 This stylistic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known A chromosome is an organized structure of DNA and Protein that is found in cells. Introns are regions often found in eukaryote genes that are removed in the splicing process (after the DNA is transcribed into RNA): only the exons encode the protein. Introns, derived from the term "intragenic regions" and also called intervening sequence (IVS are DNA regions in a Gene that are not translated into Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex In Molecular biology, splicing is a modification of an RNA after transcription, in which Introns are removed and Exons are joined An exon is a Nucleic acid sequence that is represented in the mature form of an RNA molecule after a portions of a precursor RNA Introns have been Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl This diagram labels a region of only 40 or so bases as a gene. In reality most genes are hundreds of times larger. | |
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A gene is a locatable region of genomic sequence, corresponding to a unit of inheritance, which is associated with regulatory regions, transcribed regions and/or other functional sequence regions. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby [1][2] The physical development and phenotype of organisms can be thought of as a product of genes interacting with each other and with the environment. Developmental Biology is the official journal of the Society for Developmental Biology. A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties [3] A concise definition of a gene, taking into account complex patterns of regulation and transcription, genic conservation and non-coding RNA genes, has been proposed by Gerstein et al. [4] "A gene is a union of genomic sequences encoding a coherent set of potentially overlapping functional products".
Colloquially, the term gene is often used to refer to an inheritable trait which is usually accompanied by a phenotype as in ("tall genes" or "bad genes") -- the proper scientific term for this is allele. An allele (ˈæliːl (UK /əˈliːl/ (US (from the Greek αλληλος allelos, meaning each other) is one member of a pair or series of different forms
In cells, genes consist of a long strand of DNA that contains a promoter, which controls the activity of a gene, and coding and non-coding sequence. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known In Biology, a promoter is a region of DNA that facilitates the transcription of a particular Gene. Coding sequence determines what the gene produces, while non-coding sequence can regulate the conditions of gene expression. Gene expression is the process by which inheritable information from a Gene, such as the DNA sequence, is made into a functional Gene product, such When a gene is active, the coding and non-coding sequence is copied in a process called transcription, producing an RNA copy of the gene's information. Transcription is the synthesis of RNA under the direction of DNA Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units This RNA can then direct the synthesis of proteins via the genetic code. Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins But some RNAs are used directly, for example as part of the ribosome. Ribosomes ( from ribo nucleic acid and "Greek soma ( meaning body") are complexes of RNA and Protein that These molecules resulting from gene expression, whether RNA or protein, are known as gene products. A gene product is the biochemical material either RNA or Protein, resulting from expression of a Gene.
Genes often contain regions that do not encode products, but regulate gene expression. Gene modulation redirects here For information on therapeutic regulation of gene expression see Therapeutic gene modulation. The genes of eukaryotic organisms can contain regions called introns that are removed from the messenger RNA in a process called splicing. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Introns, derived from the term "intragenic regions" and also called intervening sequence (IVS are DNA regions in a Gene that are not translated into In Molecular biology, splicing is a modification of an RNA after transcription, in which Introns are removed and Exons are joined The regions encoding gene products are called exons. An exon is a Nucleic acid sequence that is represented in the mature form of an RNA molecule after a portions of a precursor RNA Introns have been In eukaryotes, a single gene can encode multiple proteins, which are produced through the creation of different arrangements of exons through alternative splicing. Alternative splicing is the RNA splicing variation mechanism in which the Exons of the primary gene transcript the Pre-mRNA, are separated and reconnected In prokaryotes (bacteria and archaea), introns are less common and genes often contain a single uninterrupted stretch of DNA, called a cistron, that codes for a product. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Prokaryotic genes are often arranged in groups called operons with promoter and operator sequences that regulate transcription of a single long RNA. An operon is a functioning unit of key Nucleotide sequences including an operator, a common Promoter, and one or more structural Genes, In Biology, a promoter is a region of DNA that facilitates the transcription of a particular Gene. In Mathematics, an operator is a function which operates on (or modifies another function Transcription is the synthesis of RNA under the direction of DNA Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units This RNA contains multiple coding sequences. Each coding sequence is preceded by a Shine-Dalgarno sequence that ribosomes recognize. The Shine-Dalgarno sequence (or Shine-Dalgarno box proposed by Australian scientists John Shine and Lynn Dalgarno, is a ribosomal binding site
The total set of genes in an organism is known as its genome. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby An organism's genome size is generally lower in prokaryotes, both in number of base pairs and number of genes, than even single-celled eukaryotes. Genome size refers to the total amount of DNA contained within one copy of a Genome. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex However, there is no clear relationship between genome sizes and complexity in eukaryotic organisms. One of the largest known genomes belongs to the single-celled amoeba Amoeba dubia, with over 670 billion base pairs, some 200 times larger than the human genome. Amoeba (sometimes amœba or ameba, plural amoebae) is a Genus of Protozoa that moves [5] The estimated number of genes in the human genome has been repeatedly revised downward since the completion of the Human Genome Project; current estimates place the human genome at just under 3 billion base pairs and about 20,000–25,000 genes. The human genome is the Genome of Homo sapiens, which is stored on 23 chromosome pairs The Human Genome Project (HGP was an international Scientific research project with a primary goal to determine the sequence of chemical base pairs which make up DNA [6] A recent Science article gives a number of 20,488 protein-coding genes, with perhaps 100 more yet to be discovered. Science is the Academic journal of the American Association for the Advancement of Science and is considered one of the world's most prestigious Scientific [7] The gene density of a genome is a measure of the number of genes per million base pairs (called a megabase, Mb); prokaryotic genomes have much higher gene densities than eukaryotes. A megabase (Mb is a unit of length for DNA fragments equal to 1 million Nucleotides In the Human genome, one megabase is roughly equivalent to one The gene density of the human genome is roughly 12–15 genes per megabase pair. [8]
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History
The existence of genes was first suggested by Gregor Mendel (1822-1884), who, in the 1860s, studied inheritance in pea plants and hypothesized a factor that conveys traits from parent to offspring. The history of Genetics is generally held to have started with the work of an Augustinian Monk, Gregor Mendel. Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was A pea (inaccurately called a '''sweet pea''' by food distubutors is most commonly the small spherical Seed or the seed-pod of the Legume Pisum A hypothesis (from Greek) consists either of a suggested explanation for a phenomenon (an event that is observable or of a reasoned proposal suggesting a possible He spent over 10 years of his life on one experiment. Although he did not use the term gene, he explained his results in terms of inherited characteristics. Mendel was also the first to hypothesize independent assortment, the distinction between dominant and recessive traits, the distinction between a heterozygote and homozygote, and the difference between what would later be described as genotype and phenotype. Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent Zygosity refers to the genetic condition of a Zygote. In genetics zygosity describes the similarity or dissimilarity of DNA between Homologous Zygosity refers to the genetic condition of a Zygote. In genetics zygosity describes the similarity or dissimilarity of DNA between Homologous The genotype is the genetic constitution of a cell an organism or an individual (i A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties Mendel's concept was given a name by Hugo de Vries in 1889, who, at that time probably unaware of Mendel's work, in his book Intracellular Pangenesis coined the term "pangen" for "the smallest particle [representing] one hereditary characteristic". Hugo Marie de Vries ( Feb 16 1848, Haarlem - May 21 1935, Lunteren) was a Dutch Botanist and one of [9] Wilhelm Johannsen abbreviated this term to "gene" ("gen" in Danish and German) two decades later. Wilhelm Johannsen ( February 3, 1857 - November 11, 1927) was a Danish Botanist, plant physiologist and Geneticist
In the early 1900s, Mendel's work received renewed attention from scientists. In 1910, Thomas Hunt Morgan showed that genes reside on specific chromosomes. Thomas Hunt Morgan ( September 25, 1866 &ndash December 4, 1945) was an American geneticist and embryologist. A chromosome is an organized structure of DNA and Protein that is found in cells. He later showed that genes occupy specific locations on the chromosome. With this knowledge, Morgan and his students began the first chromosomal map of the fruit fly Drosophila. Drosophila melanogaster (from the Greek for black-bellied dew-lover) is a two-winged insect that belongs to the Diptera, the order In 1928, Frederick Griffith showed that genes could be transferred. Frederick Griffith (1879 - 1941 was a British medical officer and geneticist. In what is now known as Griffith's experiment, injections into a mouse of a deadly strain of bacteria that had been heat-killed transferred genetic information to a safe strain of the same bacteria, killing the mouse. Griffith's experiment, conducted in 1928 by Frederick Griffith, was one of the first experiments suggesting that bacteria are capable of transferring genetic information The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have
In 1941,George Wells Beadle and Edward Lawrie Tatum showed that mutations in genes caused errors in certain steps in metabolic pathways. George Wells Beadle ( October 22, 1903 &ndash June 9, 1989) was an American Scientist in the field of Genetics Edward Lawrie Tatum ( December 14, 1909 &ndash November 5, 1975) was an American geneticist. In Biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell. This showed that specific genes code for specific proteins, leading to the "one gene, one enzyme" hypothesis. [10] Oswald Avery, Collin Macleod, and Maclyn McCarty showed in 1944 that DNA holds the gene's information. Oswald Theodore Avery ( October 21, 1877 &ndash 2 February, 1955) was a Canadian -born American Physician and Colin Munro MacLeod ( January 28, 1909 &mdash February 11, 1972) was a Canadian-American geneticist Maclyn McCarty ( South Bend Indiana, June 9 1911 &ndash January 2 2005) was an American Geneticist. In 1953, James D. Watson and Francis Crick demonstrated the molecular structure of DNA. Francis Harry Compton Crick OM FRS (8 June 1916 – 28 July 2004 Ph Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Together, these discoveries established the central dogma of molecular biology, which states that proteins are translated from RNA which is transcribed from DNA. The central dogma of molecular biology was first enunciated by Francis Crick in 1958 and re-stated in a Nature paper published in 1970 Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units This dogma has since been shown to have exceptions, such as reverse transcription in retroviruses. Reverse transcription is the process of making a double stranded DNA (deoxyribonucleic acid molecule from a single stranded RNA (ribonucleic acid template A retrovirus is any Virus belonging to the viral family Retroviridae.
In 1972, Walter Fiers and his team at the Laboratory of Molecular Biology of the University of Ghent (Ghent, Belgium) were the first to determine the sequence of a gene: the gene for Bacteriophage MS2 coat protein. Walter Fiers (b Ieper, Belgium, 1931 is a Belgian molecular biologist Ghent University (in Dutch Universiteit Gent, abbreviated UGent) is one of the three large Flemish universities. Ghent (ˈɡɛnt Gent ʝɛnt in Dutch, Gand in French, and formerly Gaunt in English) is a City and a The Kingdom of Belgium is a Country in northwest Europe. It is a founding member of the European Union and hosts its headquarters as well as those The bacteriophage MS2. MS2 phage is an icosahedral bacteriophage with a diameter of 27-34nm and an isoelectric point (pI of 3 [11] Richard J. Roberts and Phillip Sharp discovered in 1977 that genes can be split into segments. Sir Richard John Roberts (born September 6, 1943 in Derby) is an English Biochemist and molecular biologist. Phillip Allen Sharp (born June 6, 1944) is an American Geneticist and molecular biologist who co-discovered gene splicing This leads to the idea that one gene can make several proteins. Recently (as of 2003-2006), biological results let the notion of gene appear more slippery. Foundations of modern biology There are five unifying principles In particular, genes do not seem to sit side by side on DNA like discrete beads. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Instead, regions of the DNA producing distinct proteins may overlap, so that the idea emerges that "genes are one long continuum". The article is about the geographic sense of the term For other uses including Regions and Regional, see Region (disambiguation. Continuum theories or models explain variation as involving a gradual quantitative transition without abrupt changes or discontinuities [1]
Mendelian inheritance and classical genetics
Darwin used the term Gemmule to describe a microscopic unit of inheritance, and what would later become known as Chromosomes had been observed separating out during cell division by Wilhelm Hofmeister as early as 1848. Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent Classical genetics consists of the techniques and methodologies of Genetics that predate the advent of Molecular biology. Gemmules are internal Buds found in freshwater sponges and are the result of Asexual reproduction, and resemble round food-filled balls A chromosome is an organized structure of DNA and Protein that is found in cells. Wilhelm Friedrich Benedikt Hofmeister ( 18 May 1824 to 12 January 1877) was a German Biologist and Botanist The idea that chromosomes were the carriers of inheritance was expressed in 1883 by Wilhelm Roux. Wilhelm Roux ( June 9, 1850 &ndash September 15, 1924) was a German zoologist and pioneer of experimental Embryology The modern conception of the gene originated with work by Gregor Mendel, a 19th century Augustinian monk who systematically studied heredity in pea plants. Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was The Augustinians, named after Saint Augustine of Hippo (died AD 430) are several Catholic Monastic orders and congregations Mendel's work was the first to illustrate particulate inheritance, or the theory that inherited traits are passed from one generation to the next in discrete units that interact in well-defined ways. Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent Danish botanist Wilhelm Johannsen coined the word "gene" in 1909 to describe these fundamental physical and functional units of heredity,[12] while the related word genetics was first used by William Bateson in 1905. The Kingdom of Denmark ( ˈd̥ænmɑɡ̊ (archaic ˈd̥anmɑːɡ̊ commonly known as Denmark, is a country in the Scandinavian region of northern Europe Botany, plant science(s, phytology, or plant biology is a branch of Biology and is the scientific study of plant Life Wilhelm Johannsen ( February 3, 1857 - November 11, 1927) was a Danish Botanist, plant physiologist and Geneticist Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is William Bateson ( Robin Hood's Bay, August 8 1861 &ndash February 8 1926 was a British Geneticist, a Fellow of St [10] The word was derived from Hugo De Vries' 1889 term pangen for the same concept,[9] itself a derivative of the word pangenesis coined by Darwin (1868). Hugo Marie de Vries ( Feb 16 1848, Haarlem - May 21 1935, Lunteren) was a Dutch Botanist and one of Pangenesis was Charles Darwin 's hypothetical mechanism for Heredity. Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life [13] The word pangenesis is made from the Greek words pan (a prefix meaning "whole", "encompassing") and genesis ("birth") or genos ("origin"). Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly
According to the theory of Mendelian inheritance, variations in phenotype - the observable physical and behavioral characteristics of an organism - are due to variations in genotype, or the organism's particular set of genes, each of which specifies a particular trait. A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties The genotype is the genetic constitution of a cell an organism or an individual (i Different forms of a gene, which may give rise to different phenotypes, are known as alleles. An allele (ˈæliːl (UK /əˈliːl/ (US (from the Greek αλληλος allelos, meaning each other) is one member of a pair or series of different forms Organisms such as the pea plants Mendel worked on, along with many plants and animals, have two alleles for each trait, one inherited from each parent. Alleles may be dominant or recessive; dominant alleles give rise to their corresponding phenotypes when paired with any other allele for the same trait, while recessive alleles give rise to their corresponding phenotype only when paired with another copy of the same allele. For example, if the allele specifying tall stems in pea plants is dominant over the allele specifying short stems, then pea plants that inherit one tall allele from one parent and one short allele from the other parent will also have tall stems. Mendel's work found that alleles assort independently in the production of gametes, or germ cells, ensuring variation in the next generation. A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete Germ cells are progenitors of the Gametes. These singled out cells move through the gut to the developing Gonads and undergo mitotic proliferation followed
Prior to Mendel's work, the dominant theory of heredity was one of blending inheritance, which proposes that the traits of the parents blend or mix in a smooth, continuous gradient in the offspring. In Darwin's time biologists held to the theory of blending inheritance -- an offspring was an average of its parents Although Mendel's work was largely unrecognized after its first publication in 1866, it was rediscovered in 1900 by three European scientists, Hugo de Vries, Carl Correns, and Erich von Tschermak, who had reached similar conclusions from their own research. Hugo Marie de Vries ( Feb 16 1848, Haarlem - May 21 1935, Lunteren) was a Dutch Botanist and one of Carl Erich Correns ( September 10, 1864 - February 14, 1933) was a German Botanist and Geneticist, who is notable Erich von Tschermak-Seysenegg ( November 15 1871 &ndash October 11 1962) was an Austrian Agronomist. However, these scientists were not yet aware of the identity of the 'discrete units' on which genetic material resides.
A series of subsequent discoveries led to the realization decades later that chromosomes within cells are the carriers of genetic material, and that they are made of DNA (deoxyribonucleic acid), a polymeric molecule found in all cells on which the 'discrete units' of Mendelian inheritance are encoded. A chromosome is an organized structure of DNA and Protein that is found in cells. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds The modern study of genetics at the level of DNA is known as molecular genetics and the synthesis of molecular genetics with traditional Darwinian evolution is known as the modern evolutionary synthesis. Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is Molecular genetics is the field of Biology which studies the structure and function of Genes at a molecular level Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life eVolution is the third Album by eLDee, it was due to be released in 2008
Physical definitions
The vast majority of living organisms encode their genes in long strands of DNA. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known DNA consists of a chain made from four types of nucleotide subunits: adenine, cytosine, guanine, and thymine. Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group Adenine is a Purine with a variety of roles in Biochemistry including Cellular respiration, in the form of both the energy-rich Adenosine Cytosine is one of the five main bases found in DNA and RNA. It is a Pyrimidine derivative with a Heterocyclic Aromatic ring Guanine is one of the five main Nucleobases found in the Nucleic acids DNA and RNA, the others being Adenine, Cytosine, Thymine is one of the four bases in the Nucleic acid of DNA that make up the letters ATGC Each nucleotide subunit consists of three components: a phosphate group, a deoxyribose sugar ring, and a nucleobase. A phosphate, an Inorganic chemical, is a salt of Phosphoric acid. Deoxyribose, also known as D-Deoxyribose and 2-deoxyribose, is an Aldopentose &mdash a Monosaccharide containing five Carbon Structure The "skeleton" of adenine Thus, nucleotides in DNA or RNA are typically called 'bases'; consequently they are commonly referred to simply by their purine or pyrimidine original base components adenine, cytosine, guanine, thymine. Purine ( 1) is a heterocyclic Aromatic Organic compound, consisting of a Pyrimidine ring fused to an Imidazole ring Pyrimidine is a Heterocyclic Aromatic Organic compound similar to Benzene and Pyridine, containing two Nitrogen Atoms Adenine and guanine are purines and cytosine and thymine are pyrimidines. The most common form of DNA in a cell is in a double helix structure, in which two individual DNA strands twist around each other in a right-handed spiral. In Geometry a double helix (plural helices) typically consists of two congruent helices with the same axis differing by a translation In this structure, the base pairing rules specify that guanine pairs with cytosine and adenine pairs with thymine (each pair contains one purine and one pyrimidine). In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called Guanine is one of the five main Nucleobases found in the Nucleic acids DNA and RNA, the others being Adenine, Cytosine, Cytosine is one of the five main bases found in DNA and RNA. It is a Pyrimidine derivative with a Heterocyclic Aromatic ring Adenine is a Purine with a variety of roles in Biochemistry including Cellular respiration, in the form of both the energy-rich Adenosine Thymine is one of the four bases in the Nucleic acid of DNA that make up the letters ATGC The base pairing between guanine and cytosine forms three hydrogen bonds, while the base pairing between adenine and thymine forms two hydrogen bonds. The two strands in a double helix must therefore be complementary, that is, their bases must align such that the adenines of one strand are paired with the thymines of the other strand, and so on.
Due to the chemical composition of the pentose residues of the bases, DNA strands have directionality. One end of a DNA polymer contains an exposed hydroxyl group on the deoxyribose, this is known as the 3' end of the molecule. Hydroxyl in Chemistry stands for a molecule consisting of an Oxygen atom and a Hydrogen atom connected by a Covalent bond. Deoxyribose, also known as D-Deoxyribose and 2-deoxyribose, is an Aldopentose &mdash a Monosaccharide containing five Carbon Directionality, in Molecular biology, refers to the end-to-end chemical orientation of a single strand of Nucleic acid. The other end contains an exposed phosphate group, this is the 5' end. A phosphate, an Inorganic chemical, is a salt of Phosphoric acid. Directionality, in Molecular biology, refers to the end-to-end chemical orientation of a single strand of Nucleic acid. The directionality of DNA is vitally important to many cellular processes, since double helices are necessarily directional (a strand running 5'-3' pairs with a complementary strand running 3'-5') and processes such as DNA replication occur in only one direction. DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules All nucleic acid synthesis in a cell occurs in the 5'-3' direction, because new monomers are added via a dehydration reaction that uses the exposed 3' hydroxyl as a nucleophile. Dehydration ( hypohydration) is the removal of Water ( hydro in ancient Greek) from an object In Chemistry, a nucleophile (literally nucleus lover as in nucleus and phile) is a Reagent that forms a Chemical bond to
The expression of genes encoded in DNA begins by transcribing the gene into RNA, a second type of nucleic acid that is very similar to DNA, but whose monomers contain the sugar ribose rather than deoxyribose. Gene expression is the process by which inheritable information from a Gene, such as the DNA sequence, is made into a functional Gene product, such Transcription is the synthesis of RNA under the direction of DNA Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units A nucleic acid is a Macromolecule composed of chains of monomeric Nucleotides In Biochemistry these Molecules carry Genetic information Ribose (ɹˈaɪbəʊs ɹˈaɪbəɹʊs primarily seen as D-ribose, is an Aldopentose — a Monosaccharide containing five Carbon Deoxyribose, also known as D-Deoxyribose and 2-deoxyribose, is an Aldopentose &mdash a Monosaccharide containing five Carbon RNA also contains the base uracil in place of thymine. Uracil is a common and naturally occurring Pyrimidine derivative Thymine is one of the four bases in the Nucleic acid of DNA that make up the letters ATGC RNA molecules are less stable than DNA and are typically single-stranded. Genes that encode proteins are composed of a series of three-nucleotide sequences called codons, which serve as the "words" in the genetic "language". Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins The genetic code specifies the correspondence during protein translation between codons and amino acids. The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins Translation is the first stage of Protein biosynthesis (part of the overall process of Gene expression) In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this The genetic code is nearly the same for all known organisms.
RNA genes and genomes
In some cases, RNA is an intermediate product in the process of manufacturing proteins from genes. Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units However, for other gene sequences, the RNA molecules are the actual functional products. For example, RNAs known as ribozymes are capable of enzymatic function, and miRNAs have a regulatory role. A ribozyme (from ribo nucleic acid en' zyme', also called RNA Enzyme or catalytic RNA is an RNA Molecule that catalyzes Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins In Genetics, microRNAs ( miRNA) are single-stranded RNA molecules of about 21–23 Nucleotides in length which regulate Gene expression The DNA sequences from which such RNAs are transcribed are known as RNA genes. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known A non-coding RNA ( ncRNA) is any RNA molecule that is not translated into a Protein.
Some viruses store their entire genomes in the form of RNA, and contain no DNA at all. A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable Because they use RNA to store genes, their cellular hosts may synthesize their proteins as soon as they are infected and without the delay in waiting for transcription. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called In Biology, a host is an organism that harbors a Virus or Parasite, or a mutual or Commensal Symbiont, typically providing nourishment An infection is the detrimental Colonization of a host Organism by a foreign Species. On the other hand, RNA retroviruses, such as HIV, require the reverse transcription of their genome from RNA into DNA before their proteins can be synthesized. A retrovirus is any Virus belonging to the viral family Retroviridae. Human immunodeficiency virus ( HIV) is a Lentivirus (a member of the Retrovirus family that can lead to acquired immunodeficiency syndrome Reverse transcription is the process of making a double stranded DNA (deoxyribonucleic acid molecule from a single stranded RNA (ribonucleic acid template In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby In 2006, French researchers came across a puzzling example of RNA-mediated inheritance in mouse. Mice with a loss-of-function mutation in the gene Kit have white tails. In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism Offspring of these mutants can have white tails despite having only normal Kit genes. The research team traced this effect back to mutated Kit RNA. [14] While RNA is common as genetic storage material in viruses, in mammals in particular RNA inheritance has been observed very rarely.
Functional structure of a gene
All genes have regulatory regions in addition to regions that explicitly code for a protein or RNA product. A regulatory region shared by almost all genes is known as the promoter, which provides a position that is recognized by the transcription machinery when a gene is about to be transcribed and expressed. In Biology, a promoter is a region of DNA that facilitates the transcription of a particular Gene. A gene can have more than one promoter, resulting in RNAs that differ in how far they extend in the 5' end. [15] Although promoter regions have a consensus sequence that is the most common sequence at this position, some genes have "strong" promoters that bind the transcription machinery well, and others have "weak" promoters that bind poorly. In Molecular biology and Bioinformatics, a consensus sequence is a way of representing the results of a multiple Sequence alignment, where related sequences These weak promoters usually permit a lower rate of transcription than the strong promoters, because the transcription machinery binds to them and initiates transcription less frequently. Other possible regulatory regions include enhancers, which can compensate for a weak promoter. In Genetics, an enhancer is a short region of DNA that can be bound with Proteins (namely the Trans-acting factors much like a set of Transcription Most regulatory regions are "upstream" — that is, before or toward the 5' end of the transcription initiation site. Eukaryotic promoter regions are much more complex and difficult to identify than prokaryotic promoters. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex In Biology, a promoter is a region of DNA that facilitates the transcription of a particular Gene. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other
Many prokaryotic genes are organized into operons, or groups of genes whose products have related functions and which are transcribed as a unit. An operon is a functioning unit of key Nucleotide sequences including an operator, a common Promoter, and one or more structural Genes, By contrast, eukaryotic genes are transcribed only one at a time, but may include long stretches of DNA called introns which are transcribed but never translated into protein (they are spliced out before translation). Many Genomes have been sequenced and their gene sequences are stored in general DNA sequence databases (e Introns, derived from the term "intragenic regions" and also called intervening sequence (IVS are DNA regions in a Gene that are not translated into Splicing can also occur in prokaryotic genes, but is less common than in eukaryotes. [16]
Chromosomes
The total complement of genes in an organism or cell is known as its genome, which may be stored on one or more chromosomes; the region of the chromosome at which a particular gene is located is called its locus. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby A chromosome is an organized structure of DNA and Protein that is found in cells. In the fields of Genetics and Evolutionary computation, a locus (plural loci) is a fixed position on a Chromosome such as the position of a A chromosome consists of a single, very long DNA helix on which thousands of genes are encoded. Prokaryotes - bacteria and archaea - typically store their genomes on a single large, circular chromosome, sometimes supplemented by additional small circles of DNA called plasmids, which usually encode only a few genes and are easily transferable between individuals. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have A plasmid is an extra-chromosomal DNA molecule separate from the chromosomal DNA which is capable of replicating independently of the chromosomal DNA For example, the genes for antibiotic resistance are usually encoded on bacterial plasmids and can be passed between individual cells, even those of different species, via horizontal gene transfer. Antibiotic resistance is the ability of a Microorganism to withstand the effects of Antibiotics. Although some simple eukaryotes also possess plasmids with small numbers of genes, the majority of eukaryotic genes are stored on multiple linear chromosomes, which are packed within the nucleus in complex with storage proteins called histones. In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed In Biology, histones are the chief Protein components of Chromatin. The manner in which DNA is stored on the histone, as well as chemical modifications of the histone itself, are regulatory mechanisms governing whether a particular region of DNA is accessible for gene expression. Gene expression is the process by which inheritable information from a Gene, such as the DNA sequence, is made into a functional Gene product, such The ends of eukaryotic chromosomes are capped by long stretches of repetitive sequences called telomeres, which do not code for any gene product but are present to prevent degradation of coding and regulatory regions during DNA replication. A telomere is a region of repetitive DNA at the end of Chromosomes which protects the end of the chromosome from destruction DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules The length of the telomeres tends to decrease each time the genome is replicated in preparation for cell division; the loss of telomeres has been proposed as an explanation for cellular senescence, or the loss of the ability to divide, and by extension for the aging process in organisms. Senescence refers to the biological processes of a living Organism approaching an advanced age (i Ageing or aging (American English is the accumulation of changes in an organism [17]
While the chromosomes of prokaryotes are relatively gene-dense, those of eukaryotes often contain so-called "junk DNA", or regions of DNA that serve no obvious function. In Molecular biology, junk DNA is a provisional label for the portions of the DNA sequence of a Chromosome or a Genome for which no Simple single-celled eukaryotes have relatively small amounts of such DNA, while the genomes of complex multicellular organisms, including humans, contain an absolute majority of DNA without an identified function. [6] However it now appears that, although protein-coding DNA makes up barely 2% of the human genome, about 80% of the bases in the genome may be being expressed, so the term "junk DNA" may be a misnomer. [2]
Gene expression
In all organisms, there are two major steps separating a protein-coding gene from its protein: first, the DNA on which the gene resides must be transcribed from DNA to messenger RNA (mRNA), and second, it must be translated from mRNA to protein. Gene expression is the process by which inheritable information from a Gene, such as the DNA sequence, is made into a functional Gene product, such Transcription is the synthesis of RNA under the direction of DNA Messenger ribonucleic acid ( mRNA) is a molecule of RNA encoding a chemical "blueprint" for a Protein product Translation is the first stage of Protein biosynthesis (part of the overall process of Gene expression) RNA-coding genes must still go through the first step, but are not translated into protein. The process of producing a biologically functional molecule of either RNA or protein is called gene expression, and the resulting molecule itself is called a gene product. Gene expression is the process by which inheritable information from a Gene, such as the DNA sequence, is made into a functional Gene product, such A gene product is the biochemical material either RNA or Protein, resulting from expression of a Gene.
Genetic code
The genetic code is the set of rules by which a gene is translated into a functional protein. The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins Each gene consists of a specific sequence of nucleotides encoded in a DNA (or sometimes RNA) strand; a correspondence between nucleotides, the basic building blocks of genetic material, and amino acids, the basic building blocks of proteins, must be established for genes to be successfully translated into functional proteins. Sets of three nucleotides, known as codons, each correspond to a specific amino acid or to a signal; three codons are known as "stop codons" and, instead of specifying a new amino acid, alert the translation machinery that the end of the gene has been reached. The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins There are 64 possible codons (four possible nucleotides at each of three positions, hence 43 possible codons) and only 20 standard amino acids; hence the code is redundant and multiple codons can specify the same amino acid. The correspondence between codons and amino acids is nearly universal among all known living organisms.
Transcription
The process of genetic transcription produces a single-stranded RNA molecule known as messenger RNA, whose nucleotide sequence is complementary to the DNA from which it was transcribed. Transcription is the synthesis of RNA under the direction of DNA Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units Messenger ribonucleic acid ( mRNA) is a molecule of RNA encoding a chemical "blueprint" for a Protein product The DNA strand whose sequence matches that of the RNA is known as the coding strand and the strand from which the RNA was synthesized is the template strand. When referring to DNA transcription ( Protein biosynthesis) the coding strand is the DNA strand which has the same base sequence as Sense, when applied in a Molecular biology context is a general concept used to compare the polarity of Nucleic acid molecules such as DNA or RNA Transcription is performed by an enzyme called an RNA polymerase, which reads the template strand in the 3' to 5' direction and synthesizes the RNA from 5' to 3'. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins RNA polymerase ( RNAP or RNApol) is an Enzyme that produces RNA. Directionality, in Molecular biology, refers to the end-to-end chemical orientation of a single strand of Nucleic acid. Directionality, in Molecular biology, refers to the end-to-end chemical orientation of a single strand of Nucleic acid. Directionality, in Molecular biology, refers to the end-to-end chemical orientation of a single strand of Nucleic acid. Directionality, in Molecular biology, refers to the end-to-end chemical orientation of a single strand of Nucleic acid. To initiate transcription, the polymerase first recognizes and binds a promoter region of the gene. In Biology, a promoter is a region of DNA that facilitates the transcription of a particular Gene. Thus a major mechanism of gene regulation is the blocking or sequestering of the promoter region, either by tight binding by repressor molecules that physically block the polymerase, or by organizing the DNA so that the promoter region is not accessible. Gene modulation redirects here For information on therapeutic regulation of gene expression see Therapeutic gene modulation. For other uses see Repression A repressor is a DNA-binding protein that regulates the expression of one or more genes by decreasing
In prokaryotes, transcription occurs in the cytoplasm; for very long transcripts, translation may begin at the 5' end of the RNA while the 3' end is still being transcribed. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. In eukaryotes, transcription necessarily occurs in the nucleus, where the cell's DNA is sequestered; the RNA molecule produced by the polymerase is known as the primary transcript and must undergo post-transcriptional modifications before being exported to the cytoplasm for translation. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex A primary transcript is an RNA molecule that has not yet undergone any modification after its synthesis. Post-transcriptional modification is a process in Cell biology by which in Eukaryotic cells, primary transcript RNA is converted into mature The splicing of introns present within the transcribed region is a modification unique to eukaryotes; alternative splicing mechanisms can result in mature transcripts from the same gene having different sequences and thus coding for different proteins. In Molecular biology, splicing is a modification of an RNA after transcription, in which Introns are removed and Exons are joined Introns, derived from the term "intragenic regions" and also called intervening sequence (IVS are DNA regions in a Gene that are not translated into Alternative splicing is the RNA splicing variation mechanism in which the Exons of the primary gene transcript the Pre-mRNA, are separated and reconnected This is a major form of regulation in eukaryotic cells.
Translation
Translation is the process by which a mature mRNA molecule is used as a template for synthesizing a new protein. Translation is the first stage of Protein biosynthesis (part of the overall process of Gene expression) Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl Translation is carried out by ribosomes, large complexes of RNA and protein responsible for carrying out the chemical reactions to add new amino acids to a growing polypeptide chain by the formation of peptide bonds. Ribosomes ( from ribo nucleic acid and "Greek soma ( meaning body") are complexes of RNA and Protein that In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this Peptides (from the Greek πεπτίδια, "small digestibles" are short Polymers formed from the linking in a defined order of α- Amino A peptide bond is a Chemical bond formed between two Molecules when the Carboxyl group of one molecule reacts with the The genetic code is read three nucleotides at a time, in units called codons, via interactions with specialized RNA molecules called transfer RNA (tRNA). The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins Transfer RNA (abbreviated tRNA) is a small RNA (usually about 74-95 nucleotides that transfers a specific Amino acid to a growing polypeptide chain at Each tRNA has three unpaired bases known as the anticodon that are complementary to the codon it reads; the tRNA is also covalently attached to the amino acid specified by the complementary codon. Transfer RNA (abbreviated tRNA) is a small RNA (usually about 74-95 nucleotides that transfers a specific Amino acid to a growing polypeptide chain at In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this When the tRNA binds to its complementary codon in an mRNA strand, the ribosome ligates its amino acid cargo to the new polypeptide chain, which is synthesized from amino terminus to carboxyl terminus. The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal end, or During and after its synthesis, the new protein must fold to its active three-dimensional structure before it can carry out its cellular function. Protein folding is the physical process by which a Polypeptide folds into its characteristic and functional three-dimensional structure. In Biochemistry and Chemistry, the tertiary structure of a Protein or any other Macromolecule is its three-dimensional structure as defined
DNA replication and inheritance
The growth, development, and reproduction of organisms relies on cell division, or the process by which a single cell divides into two usually identical daughter cells. Cell division is a process by which a cell, called the parent cell divides into two or more cells called daughter cells. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Cell division is a process by which a cell, called the parent cell divides into two or more cells called daughter cells. This requires first making a duplicate copy of every gene in the genome in a process called DNA replication. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules The copies are made by specialized enzymes known as DNA polymerases, which "read" one strand of the double-helical DNA, known as the template strand, and synthesize a new complementary strand. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins A DNA Polymerase is an Enzyme that assists in DNA replication. Because the DNA double helix is held together by base pairing, the sequence of one strand completely specifies the sequence of its complement; hence only one strand needs to be read by the enzyme to produce a faithful copy. In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called The process of DNA replication is semiconservative; that is, the copy of the genome inherited by each daughter cell contains one original and one newly synthesized strand of DNA. Semiconservative replication describes the method by which DNA is replicated in all known cells [8]
After DNA replication is complete, the cell must physically separate the two copies of the genome and divide into two distinct membrane-bound cells. In prokaryotes - bacteria and archaea - this usually occurs via a relatively simple process called binary fission, in which each circular genome attaches to the cell membrane and is separated into the daughter cells as the membrane invaginates to split the cytoplasm into two membrane-bound portions. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Binary fission is the form of Asexual reproduction and Cell division used by Prokaryotic organisms (such as Bacteria or Archea) The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer Invagination means to fold inward or to sheath In Biology, this can refer to a number of processes The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. Binary fission is extremely fast compared to the rates of cell division in eukaryotes. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Eukaryotic cell division is a more complex process known as the cell cycle; DNA replication occurs during a phase of this cycle known as S phase, while the process of segregating chromosomes and splitting the cytoplasm occurs during M phase. The cell cycle, or cell-division cycle, is the series of events that take place in a eukaryotic cell leading to its replication The S phase, short for synthesis phase, is a period in the Cell cycle during Interphase, between G1 phase and the G2 phase. A chromosome is an organized structure of DNA and Protein that is found in cells. The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. Mitosis is the process in which a Eukaryotic cell separates the Chromosomes in its Cell nucleus, into two identical sets in two daughter nuclei In many single-celled eukaryotes such as yeast, reproduction by budding is common, which results in asymmetrical portions of cytoplasm in the two daughter cells. Yeasts are a growth form of eukaryotic Microorganisms classified in the kingdom Fungi, with about 1500 Species currently described Budding (also called burgeoning) is the formation of a new Organism by the protrusion of part of another organism
Molecular inheritance
The duplication and transmission of genetic material from one generation of cells to the next is the basis for molecular inheritance, and the link between the classical and molecular pictures of genes. Organisms inherit the characteristics of their parents because the cells of the offspring contain copies of the genes in their parents' cells. In asexually reproducing organisms, the offspring will be a genetic copy or clone of the parent organism. Asexual reproduction is a form of reproduction which does not involve Meiosis, Ploidy reduction or Fertilization. Molecular cloning refers to the procedure of isolating a defined DNA sequence and obtaining multiple copies of it In vivo. In sexually reproducing organisms, a specialized form of cell division called meiosis produces cells called gametes or germ cells that are haploid, or contain only one copy of each gene. The Evolution of sexual reproduction is a major puzzle The first Fossilized evidence of sexually reproducing Organisms is from Eukaryotes of the Stenian In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete Germ cells are progenitors of the Gametes. These singled out cells move through the gut to the developing Gonads and undergo mitotic proliferation followed "Haplo" redirects here For the fictional character see The Death Gate Cycle. The gametes produced by females are called eggs or ova, and those produced by males are called sperm. In most Birds and Reptiles an egg ( Latin ovum) is the Zygote, resulting from Fertilization of the Ovum. The term sperm is derived from the Greek word (σπέρμα sperma (meaning "seed" and refers to the male reproductive cells. Two gametes fuse to form a fertilized egg, a single cell that once again has a diploid number of genes - each with one copy from the mother and one copy from the father. For other meanings see Zygote (disambiguation. A zygote (from Greek ζυγωτός zugōtos "joined" or "yoked" "Haplo" redirects here For the fictional character see The Death Gate Cycle.
During the process of meiotic cell division, an event called genetic recombination or crossing-over can sometimes occur, in which a length of DNA on one chromatid is swapped with a length of DNA on the corresponding sister chromatid. Genetic recombination is the process by which a strand of genetic material (usually DNA; but can also be RNA) is broken and then joined to a different DNA molecule A chromatid is one of two identical copies of DNA making up a replicated Chromosome, which are joined at their Centromeres for the process of Cell division This has no effect if the alleles on the chromatids are the same, but results in reassortment of otherwise linked alleles if they are different. An allele (ˈæliːl (UK /əˈliːl/ (US (from the Greek αλληλος allelos, meaning each other) is one member of a pair or series of different forms The Mendelian principle of independent assortment asserts that each of a parent's two genes for each trait will sort independently into gametes; which allele an organism inherits for one trait is unrelated to which allele it inherits for another trait. This is in fact only true for genes that do not reside on the same chromosome, or are located very far from one another on the same chromosome. The closer two genes lie on the same chromosome, the more closely they will be associated in gametes and the more often they will appear together; genes that are very close are essentially never separated because it is extremely unlikely that a crossover point will occur between them. This is known as genetic linkage. Genetic linkage occurs when particular genetic loci or Alleles for genes are inherited jointly
Mutation
DNA replication is for the most part extremely accurate, with an error rate per site of around 10-6 to 10-10 in eukaryotes. In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex [8] Rare, spontaneous alterations in the base sequence of a particular gene arise from a number of sources, such as errors in DNA replication and the aftermath of DNA damage. DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its Genome. These errors are called mutations. In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism The cell contains many DNA repair mechanisms for preventing mutations and maintaining the integrity of the genome; however, in some cases — such as breaks in both DNA strands of a chromosome — repairing the physical damage to the molecule is a higher priority than producing an exact copy. DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its Genome. Due to the degeneracy of the genetic code, some mutations in protein-coding genes are silent, or produce no change in the amino acid sequence of the protein for which they code; for example, the codons UCU and UUC both code for serine, so the U↔C mutation has no effect on the protein. The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins Serine (abbreviated as Ser or S) is an Organic compound with the formula H[[oxygen O]]2 CCH NH sub>2CH2OH Mutations that do have phenotypic effects are most often neutral or deleterious to the organism, but sometimes they confer benefits to the organism's fitness. Fitness (often denoted w in Population genetics models is a central concept in evolutionary theory.
Mutations propagated to the next generation lead to variations within a species' population. Generation (from the Greek γενεά) also known as procreation, is the act of producing Offspring. Variants of a single gene are known as alleles, and differences in alleles may give rise to differences in traits. An allele (ˈæliːl (UK /əˈliːl/ (US (from the Greek αλληλος allelos, meaning each other) is one member of a pair or series of different forms An allele (ˈæliːl (UK /əˈliːl/ (US (from the Greek αλληλος allelos, meaning each other) is one member of a pair or series of different forms Although it is rare for the variants in a single gene to have clearly distinguishable phenotypic effects, certain well-defined traits are in fact controlled by single genetic loci. A gene's most common allele is called the wild type allele, and rare alleles are called mutants. Wild type, sometimes written wildtype or wild-type, is the typical form of an organism strain gene or characteristic as it occurs in nature A mutant is an individual organism or new genetic character arising or resulting from an instance of Mutation, which is a base-pair sequence change within the DNA However, this does not imply that the wild-type allele is the ancestor from which the mutants are descended. An ancestor is a Parent or ( recursively) the parent of an ancestor (i A mutant is an individual organism or new genetic character arising or resulting from an instance of Mutation, which is a base-pair sequence change within the DNA
Genome
Chromosomal organization
The total complement of genes in an organism or cell is known as its genome. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby In prokaryotes, the vast majority of genes are located on a single chromosome of circular DNA, while eukaryotes usually possess multiple individual linear DNA helices packed into dense DNA-protein complexes called chromosomes. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex A chromosome is an organized structure of DNA and Protein that is found in cells. Extrachromosomal DNA is present in many prokaryotes and some simple eukaryotes as small, circular pieces of DNA called plasmids, which usually contain only a few genes each. Extrachromosomal DNA (sometimes called extranuclear DNA or nonchromosomal DNA is DNA located or maintained in a cell apart from the Chromosomes. A plasmid is an extra-chromosomal DNA molecule separate from the chromosomal DNA which is capable of replicating independently of the chromosomal DNA Generally, regulatory regions and junk DNA are considered to be part of an organism's genome, but structural regions such as telomeres are not. A telomere is a region of repetitive DNA at the end of Chromosomes which protects the end of the chromosome from destruction The location (or locus) of a gene and the chromosome on which it is situated is in a sense arbitrary. In the fields of Genetics and Evolutionary computation, a locus (plural loci) is a fixed position on a Chromosome such as the position of a Genes that appear together on the chromosomes of one species, such as humans, may appear on separate chromosomes in another species, such as mice. A mouse (plural mice) is a small Animal that belongs to one Two genes positioned near one another on a chromosome may encode proteins that figure in the same cellular process or in completely unrelated processes. As an example of the former, many of the genes involved in spermatogenesis reside together on the Y chromosome. Spermatogenesis is the process by which male Spermatogonia develop into mature Spermatozoa. A sex-determination system is a biological system that determines the development of sexual characteristics in an Organism.
Many species carry more than one copy of their genome within each of their somatic cells. Somatic cells are any cells forming the body of an organism as opposed to Germline cells Cells or organisms with only one copy of each gene are called haploid; those with two copies are called diploid; and those with more than two copies are called polyploid. "Haplo" redirects here For the fictional character see The Death Gate Cycle. "Haplo" redirects here For the fictional character see The Death Gate Cycle. Polyploidy occurs in cells and Organisms when there are more than two homologous sets of Chromosomes. When more than one copy is present, the two copies are not necessarily identical; in sexually reproducing organisms, one copy is normally inherited from each parent. The copies may contain distinct DNA sequences encoding distinct alleles.
Composition of the genome
| Species | Number of genes |
|---|---|
| Mycoplasma genitalium | 500 |
| Streptococcus pneumoniae | 2,300 |
| Escherichia coli | 4,400 |
| Saccharomyces cerevisiae | 5,800 |
| Drosophila melanogaster | 13,700 |
| Caenorhabditis elegans | 19,000 |
| Homo sapiens | 20,500[7] |
| Sea urchin | 23,300 |
| Arabidopsis thaliana | 25,500 |
| Mus musculus | 29,000 |
| Oryza sativa | 50,000 |
Typical numbers of genes and size of genomes vary widely among organisms, even those that are fairly closely evolutionarily related. Mycoplasma genitalium is a small parasitic bacterium which lives on the Ciliated Epithelial cells of the Primate genital Streptococcus pneumoniae, or pneumococcus, is a Gram-positive, alpha-hemolytic diplococcus aerotolerant anaerobe and a member of the Genus Saccharomyces cerevisiae is a Species of Budding Yeast. It is perhaps the most useful Yeast owing to its use since ancient times Drosophila melanogaster (from the Greek for black-bellied dew-lover) is a two-winged insect that belongs to the Diptera, the order Caenorhabditis elegans (ˌsiːnoʊræbˈdaɪtɪs ˈɛlɪgænz is a free-living Nematode (roundworm about 1 mm in length which Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Sea urchins are small globular spiny sea cat animals composing most of class Echinoidea. Arabidopsis thaliana ( A-ra-bi-dóp-sis tha-li-á-na; thale cress, mouse-ear cress or Arabidopsis) is a small The House Mouse ( Mus musculus) is one of the most numerous species of the genus Mus commonly termed a Mouse. Rice is a Cereal foodstuff which forms an important part of the diet of many people worldwide and as such it is a staple food for many In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby eVolution is the third Album by eLDee, it was due to be released in 2008 Although it was believed before the completion of the Human Genome Project that the human genome would contain many more genes than simpler animals such as mice or fruit flies, the completion of the project has revealed that the human genome has an unexpectedly low gene density. The Human Genome Project (HGP was an international Scientific research project with a primary goal to determine the sequence of chemical base pairs which make up DNA The human genome is the Genome of Homo sapiens, which is stored on 23 chromosome pairs A mouse (plural mice) is a small Animal that belongs to one Drosophila is a Genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" [6] Estimates of the number of genes in a genome are difficult to compile because they depend on gene finding algorithms that search for patterns resembling those present in known genes, such as open reading frames, promoter regions with sequences resembling the consensus promoter sequence, and related regulatory regions such as TATA boxes in eukaryotes. Gene finding typically refers to the area of Computational biology that is concerned with algorithmically identifying stretches of sequence usually genomic DNA In Mathematics, Computing, Linguistics and related subjects an algorithm is a sequence of finite instructions often used for Calculation An open reading frame ( ORF) is a portion of an organism's Genome which contains a sequence of bases that could potentially encode a Protein In Biology, a promoter is a region of DNA that facilitates the transcription of a particular Gene. In Molecular biology and Bioinformatics, a consensus sequence is a way of representing the results of a multiple Sequence alignment, where related sequences The TATA box (also called Goldberg-Hogness box) is a DNA sequence ( Cis-regulatory element) found in the Promoter region of most genes in Gene finding is less reliable in eukaryotic than in prokaryotic genomes due to the presence of non-coding DNA such as introns and pseudogenes. Introns, derived from the term "intragenic regions" and also called intervening sequence (IVS are DNA regions in a Gene that are not translated into Pseudogenes are defunct relatives of known Genes that have lost their Protein -coding ability or are otherwise no longer expressed [18] Computational gene finding methods are still significantly more reliable than earlier techniques that required mapping the locations of specific mutations that gave rise to distinguishable alleles. [8]
In most eukaryotic species, very little of the DNA in the genome encodes proteins, and the genes may be separated by vast regions of non-coding DNA, much of which has been labeled "junk DNA" due to its apparent lack of function in the modern organism. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex In Genetics, non-coding DNA describes DNA which does not contain instructions for making Proteins (or other cell products such as Noncoding In Molecular biology, junk DNA is a provisional label for the portions of the DNA sequence of a Chromosome or a Genome for which no A commonly studied type of "junk DNA" is the pseudogenes, or region of non-coding DNA that resembles expressed genes but usually lacks appropriate promoters and other control sequences; such regions are hypothesized to be the results of gene duplication events in a lineage's evolutionary past. Pseudogenes are defunct relatives of known Genes that have lost their Protein -coding ability or are otherwise no longer expressed Gene duplication (or chromosomal duplication) is any duplication of a region of DNA that contains a Gene; it may occur as an error in Homologous eVolution is the third Album by eLDee, it was due to be released in 2008 [19] Moreover, the genes are often fragmented internally by non-coding sequences called introns, which can be many times longer than the coding sequence but are spliced during post-transcriptional modification of pre-mRNA. Introns, derived from the term "intragenic regions" and also called intervening sequence (IVS are DNA regions in a Gene that are not translated into In Molecular biology, splicing is a modification of an RNA after transcription, in which Introns are removed and Exons are joined Post-transcriptional modification is a process in Cell biology by which in Eukaryotic cells, primary transcript RNA is converted into mature Messenger ribonucleic acid ( mRNA) is a molecule of RNA encoding a chemical "blueprint" for a Protein product
Genetic and genomic nomenclature
Gene nomenclature has been established by the HUGO Gene Nomenclature Committee (HGNC) for each known human gene in the form of an approved gene name and symbol (short-form abbreviation). Gene nomenclature is the scientific naming of Genes, the units of heredity in living organisms The Human Genome Organisation (HUGO is an organization involved in the Human Genome Project, a project about mapping the human genome The musical instrument is spelled Cymbal. A symbol is something --- such as an object, Picture, written word a sound a piece For the HTML tag see HTML element. An abbreviation (from Latin brevis "short" All approved symbols are stored in the HGNC Database. Each symbol is unique and each gene is only given one approved gene symbol. It is necessary to provide a unique symbol for each gene so that people can talk about them. This also facilitates electronic data retrieval from publications. Electronics refers to the flow of charge (moving Electrons through Nonmetal conductors (mainly Semiconductors, whereas electrical Debt AIDS Trade in Africa (or DATA) is a Multinational non-government organization founded in January 2002 in London by U2 's In preference each symbol maintains parallel construction in different members of a gene family and can be used in other species, especially the mouse. A gene family is a set of Genes with a known homology. They are generally biochemically similar In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. A mouse (plural mice) is a small Animal that belongs to one
Evolutionary concept of a gene
George C. Williams first explicitly advocated the gene-centric view of evolution in his 1966 book Adaptation and Natural Selection. Professor George Christopher Williams (b May 12 1926 is an American Evolutionary biologist. The gene-centered view of evolution, gene selection theory or selfish gene theory holds that Natural selection acts through differential survival of competing Adaptation and Natural Selection A Critique of Some Current Evolutionary Thought is a 1966 book by the American Evolutionary biologist He proposed an evolutionary concept of gene to be used when we are talking about natural selection favoring some genes. Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of The definition is: "that which segregates and recombines with appreciable frequency. " According to this definition, even an asexual genome could be considered a gene, insofar that it have an appreciable permanency through many generations. Asexuality is a Sexual orientation that describes individuals who do not experience Sexual attraction.
The difference is: the molecular gene transcribes as a unit, and the evolutionary gene inherits as a unit.
Richard Dawkins' The Selfish Gene and The Extended Phenotype defended the idea that the gene is the only replicator in living systems. Clinton Richard Dawkins, FRS, FRSL (born 26 March 1941 is a British ethologist, evolutionary biologist, and Popular science The Extended Phenotype (subtitled "The Gene as the Unit of Selection" and later "The Long Reach of the Gene" is a 1982 book by Richard DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules This means that only genes transmit their structure largely intact and are potentially immortal in the form of copies. So, genes should be the unit of selection. A unit of selection is a biological entity within the hierarchy of biological organisation (e In The Selfish Gene Dawkins attempts to redefine the word 'gene' to mean "an inheritable unit" instead of the generally accepted definition of "a section of DNA coding for a particular protein". In River Out of Eden, Dawkins further refined the idea of gene-centric selection by describing life as a river of compatible genes flowing through geological time. River out of Eden (subtitled "A Darwinian View of Life" is a 1995 Popular science book by Richard Dawkins. The geologic time scale is a chronologic schema (or idealized Model) relating Stratigraphy to time that is used by Geologists and other Scoop up a bucket of genes from the river of genes, and we have an organism serving as temporary bodies or survival machines. A river of genes may fork into two branches representing two non-interbreeding species as a result of geographical separation. In Biology, hybrid has two meanings The first meaning is the result of interbreeding between two animals or plants of different taxa. In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank.
Gene targeting and implications
Gene targeting is commonly referred to techniques for altering or disrupting mouse genes and provides the mouse models for studying the roles of individual genes in embryonic development, human disorders, aging and diseases. Embryogenesis is the process by which the Embryo is formed and develops The mouse models, where one or more of its genes are deactivated or made inoperable, are called knockout mice. A knockout mouse is a genetically engineered mouse in which one or more Genes have been turned off through a Gene knockout. Since the first reports in which homologous recombination in embryonic stem cells was used to generate gene-targeted mice,[20] gene targeting has proven to be a powerful means of precisely manipulating the mammalian genome, producing at least ten thousand mutant mouse strains and it is now possible to introduce mutations that can be activated at specific time points, or in specific cells or organs, both during development and in the adult animal. Homologous recombination is a type of Genetic recombination, a process of physical rearrangement occurring between two strands of DNA. Embryonic stem cells (ES cells are Stem cells derived from the inner cell mass of an early stage Embryo known as a Blastocyst. [21][22]
Gene targeting strategies have been expanded to all kinds of modifications, including point mutations, isoform deletions, mutant allele correction, large pieces of chromosomal DNA insertion and deletion, tissue specific disruption combined with spatial and temporal regulation and so on. A point mutation, or single base substitution, is a type of Mutation that causes the replacement of a single base nucleotide with another nucleotide of the genetic Genetic Insertion is the addition of one or more Nucleotide Base pairs into a genetic sequence In Genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) is a Mutation (a genetic aberration It is predicted that the ability to generate mouse models with predictable phenotypes will have a major impact on studies of all phases of development, immunology, neurobiology, oncology, physiology, metabolism, and human diseases. Immunology is a broad branch of biomedical Science that covers the study of all aspects of the Immune system in all Organisms It deals with Neurobiology is the study of cells of the Nervous system and the organization of these cells into functional circuits that process information and mediate behavior Oncology is the branch of medicine that studies Tumors ( Cancer) and seeks to understand their development diagnosis treatment and prevention Physiology (from Greek grc φύσις physis, "nature origin" and grc -λογία -logia) is the study of the mechanical physical Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. Gene targeting is also in theory applicable to species from which totipotent embryonic stem cells can be established, and therefore may offer a potential to the improvement of domestic animals and plants. Totipotency is the ability of a single cell to divide and produce all the differentiated cells in an Organism, including extraembryonic tissues [22][23]
Changing concept
The concept of the gene has changed considerably (see history section). History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Originally considered a "unit of inheritance" to a usually DNA-based unit that can exert its effects on the organism through RNA or protein products. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl It was also previously believed that one gene makes one protein; this concept has been overthrown by the discovery of alternative splicing and trans-splicing. Alternative splicing is the RNA splicing variation mechanism in which the Exons of the primary gene transcript the Pre-mRNA, are separated and reconnected Trans -splicing is a special form of RNA processing in Eukaryotes where Exons from two different primary RNA transcripts are joined end to end and [10]
And the definition of gene is still changing. The first cases of RNA-based inheritance have been discovered in mammals. Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units [14] In plants, cases of traits reappearing after several generations of absence have led researchers to hypothesise RNA-directed overwriting of genomic DNA. [24] Evidence is also accumulating that the control regions of a gene do not necessarily have to be close to the coding sequence on the linear molecule or even on the same chromosome. In Genetics, an enhancer is a short region of DNA that can be bound with Proteins (namely the Trans-acting factors much like a set of Transcription The coding region of a Gene is the portion of DNA or RNA that is transcribed into another RNA, such as a messenger RNA Spilianakis and colleagues discovered that the promoter region of the interferon-gamma gene on chromosome 10 and the regulatory regions of the T(H)2 cytokine locus on chromosome 11 come into close proximity in the nucleus possibly to be jointly regulated. In Biology, a promoter is a region of DNA that facilitates the transcription of a particular Gene. Interferon-gamma ( IFN-γ) is a Dimerized soluble Cytokine that is the only member of the type II class of Interferons This interferon was originally Cytokines are a category of signalling Proteins and Glycoproteins that like Hormones and Neurotransmitters, are used extensively in cellular In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed [25]
The concept that genes are clearly delimited is also being eroded. There is evidence for fused proteins stemming from two adjacent genes that can produce two separate protein products. While it is not clear whether these fusion proteins are functional, the phenomena is more frequent than previously thought. [26] Even more ground-breaking than the discovery of fused genes is the observation that some proteins can be composed of exons from far away regions and even different chromosomes. An exon is a Nucleic acid sequence that is represented in the mature form of an RNA molecule after a portions of a precursor RNA Introns have been [27][2] This new data has led to an updated, and probably tentative, definition of a gene as "a union of genomic sequences encoding a coherent set of potentially overlapping functional products. "[10] This new definition categorizes genes by functional products, whether they be proteins or RNA, rather than specific DNA loci; all regulatory elements of DNA are therefore classified as gene-associated regions. [10]
See also
References
- ^ a b Pearson H (2006). Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known In Biology, the term epigenetics refers to changes in Gene expression caused by mechanisms other than changes in the underlying DNA sequence The gene-centered view of evolution, gene selection theory or selfish gene theory holds that Natural selection acts through differential survival of competing Gene expression is the process by which inheritable information from a Gene, such as the DNA sequence, is made into a functional Gene product, such A gene family is a set of Genes with a known homology. They are generally biochemically similar In Population genetics, a gene pool is the complete set of unique Alleles in a Species or Population. Gene therapy is the insertion of Genes into an individual's cells and tissues to treat a Disease, and Hereditary diseases in which a A genetic algorithm (GA is a Search technique used in Computing to find exact or Approximate solutions to optimization and Search In Artificial intelligence, genetic programming (GP is an Evolutionary algorithm based methodology inspired by Biological evolution to find A Gene regulatory network (also called a GRN or genetic regulatory network) is a collection of DNA segments in a cell which interact with each Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby Genomics is the study of an organism's entire Genome. The field includes intensive efforts to determine the entire DNA sequence of organisms and fine-scale Genetic A homeobox is a DNA sequence found within Genes that are involved in the regulation of patterns of development ( Morphogenesis) in Animals The Human Genome Project (HGP was an international Scientific research project with a primary goal to determine the sequence of chemical base pairs which make up DNA This list describes some of the most notable Genes present in the Human genome. A meme (miːm consists of any idea or behavior that can pass from one person to another by learning or imitation Pseudogenes are defunct relatives of known Genes that have lost their Protein -coding ability or are otherwise no longer expressed Gene modulation redirects here For information on therapeutic regulation of gene expression see Therapeutic gene modulation. A smart gene is an artificially constructed Genetic Molecule (known as a construct) composed of one or more Genes encoding a Protein "Genetics: what is a gene?". Nature 441 (7092): 398–401. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16724031.
- ^ a b c Elizabeth Pennisi (2007). "DNA Study Forces Rethink of What It Means to Be a Gene". Science 316 (5831): 1556–1557. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ see eg Martin Nowak's Evolutionary Dynamics
- ^ Gerstein MB, Bruce C, Rozowsky JS, Zheng D, Du J, Korbel JO, Emanuelsson O, Zhang ZD, Weissman S, Snyder M (2007). Martin Nowak is director of the Program for Evolutionary Dynamics at Harvard University. "What is a gene, post-ENCODE? History and updated definition". Genome Research 17 (6): 669–681. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17567988.
- ^ Cavalier-Smith T. (1985). Eukaryotic gene numbers, non-coding DNA, and genome size. In Cavalier-Smith T, ed. The Evolution of Genome Size Chichester: John Wiley.
- ^ a b c International Human Genome Sequencing Consortium (2004). "Finishing the euchromatic sequence of the human genome.". Nature 431 (7011): 931–45. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15496913.
- ^ a b Pennisi, Elizabeth (2007). "Working the (Gene Count) Numbers_ Finally, a Firm Answer". Science 316 (5828): 1113. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ a b c d e Watson JD, Baker TA, Bell SP, Gann A, Levine M, Losick R (2004). Molecular Biology of the Gene, 5th ed. , Peason Benjamin Cummings (Cold Spring Harbor Laboratory Press). ISBN 080534635X.
- ^ a b Vries, H. de (1889) Intracellular Pangenesis [1] ("pangen" definition on page 7 and 40 of this 1910 translation in English)
- ^ a b c d e Mark B. Gerstein et al. , "What is a gene, post-ENCODE? History and updated definition," Genome Research 17(6) (2007): 669-681
- ^ Min Jou W, Haegeman G, Ysebaert M, Fiers W (1972). "Nucleotide sequence of the gene coding for the bacteriophage MS2 coat protein". Nature 237 (5350): 82–8. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 4555447.
- ^ The Human Genome Project Timeline. Retrieved on 2006-09-13. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 509 BC - The Temple of Jupiter on Rome 's Capitoline Hill is dedicated on the ides of September
- ^ Darwin C. (1868). Animals and Plants under Domestication (1868).
- ^ a b Rassoulzadegan M, Grandjean V, Gounon P, Vincent S, Gillot I, Cuzin F (2006). "RNA-mediated non-mendelian inheritance of an epigenetic change in the mouse". Nature 441 (7092): 469–74. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16724059.
- ^ Mortazavi A, Williams BA, McCue K, Schaeffer L, Wold B (May 2008). "Mapping and quantifying mammalian transcriptomes by RNA-Seq". Nat. Methods. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 18516045.
- ^ Woodson SA (1998). "Ironing out the kinks: splicing and translation in bacteria". Genes Dev. 12 (9): 1243–7. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 9573040.
- ^ Braig M, Schmitt C (2006). "Oncogene-induced senescence: putting the brakes on tumor development". Cancer Res 66 (6): 2881–4. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16540631.
- ^ Mount, DW (2004). Bioinformatics: Sequence and genome analysis, 2nd ed. , Cold Spring Harbor Laboratory Press: Cold Spring Harbor, New York. ISBN 0879697121.
- ^ Lodish, H, Berk A, Matsudaira P, Kaiser CA, Krieger M, Scott MP, Zipursky SL, Darnell J. (2004). Molecular Cell Biology, 5th, New York: WH Freeman.
- ^ Thomas KR, Capecchi MR. Site-directed mutagenesis by gene targeting in mouse embryo-derived stem cells. Cell. 1987;51:503-12
- ^ The 2007 Nobel Prize in Physiology or Medicine - Press Release
- ^ a b Deng C. In Celebration of Dr. Mario R. Capecchi's Nobel Prize. Int J Biol Sci 2007; 3:417-419. http://www.biolsci.org/v03p0417.htm
- ^ Mario R. Capecchi
- ^ Lolle & colleagues (2005) Genome-wide non-mendelian inheritance of extra-genomic information in Arabidopsis. PMID 15785770
- ^ Spilianakis & colleagues (2005) Interchromosomal associations between alternatively expressed loci. PMID 15880101
- ^ Parra & colleagues (2006) Tandem chimerism as a means to increase protein complexity in the human genome. PMID 16344564
- ^ Kapranov & colleagues (2005) Examples of the complex architecture of the human transcriptome revealed by RACE and high-density tiling arrays. RACE, or Rapid Amplification of cDNA Ends, is a technique used in Molecular biology to obtain the partial sequence of an RNA transcript found within a cell PMID 15998911
Further reading
- Dawkins, Richard (1990). Clinton Richard Dawkins, FRS, FRSL (born 26 March 1941 is a British ethologist, evolutionary biologist, and Popular science The Selfish Gene. Oxford University Press. ISBN 0-19-286092-5. Google Book Search; first published 1976.
- Dawkins, Richard (1995). Clinton Richard Dawkins, FRS, FRSL (born 26 March 1941 is a British ethologist, evolutionary biologist, and Popular science River Out of Eden. River out of Eden (subtitled "A Darwinian View of Life" is a 1995 Popular science book by Richard Dawkins. Basic Books. ISBN 0-465-06990-8.
External links
Tutorial and news
- Science aid: Genetics for beginners
- Recount slashes number of human genes (from New Scientist magazine)
- National Human Genome Research Institute — News Release
- "Finishing the euchromatic sequence of the human genome" (2004). New Scientist is a weekly International science magazine and website covering recent developments in science and technology for a general English -speaking Nature 431 (7011): 931–45. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15496913.
References and databases
- Bioinformatic Harvester A Meta search engine (29 databases) for gene and protein information.
- HUGO Gene Nomenclature Committee, HGNC
- OMIM NIH's National Library of Medicine NCBI website link to Online Mendelian Inheritance in Man.
- Human Genome Organisation, HUGO
- iHOP - Information Hyperlinked over Proteins
- UniProt
- Entrez Gene - A searchable database of genes
- IDconverter - Map your ids to other known public DBs
- GeneCards - the Human Gene Compendium
- Gene Therapy Net
Dictionary
gene
-noun
- (genetics) A unit of heredity; a segment of DNA or RNA that is transmitted from one generation to the next, and that carries genetic information such as the sequence of amino acids for a protein.
Gene
-proper noun
- A diminutive of Eugene, also used as a formal male given name.
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