Part of the Biology series on

Evolution

Mechanisms and processes

Adaptation Genetic drift Gene flow Mutation Natural selection Speciation

Research and history

Evidence Evolutionary history of life History Modern synthesis Social effect / Objections

Evolutionary biology fields

Cladistics Ecological genetics Evolutionary development Human evolution Molecular evolution Phylogenetics Population genetics

Biology Portal · v • d • e

In biology, mutations are changes to the nucleotide sequence of the genetic material of an organism. Foundations of modern biology There are five unifying principles eVolution is the third Album by eLDee, it was due to be released in 2008 An adaptation is a characteristic of an Organism that has been favored by Natural selection and In Population genetics, genetic drift is the accumulation of random events that change the makeup of a gene pool slightly but often compound over time In Population genetics, gene flow (also known as gene migration) is the transfer of Alleles of Genes from one Population to another Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of Speciation is the Evolutionary process by which new biological Species arise The wide range of evidence of common descent of living things strongly indicates the occurrence of Evolution and provides a wealth of information on the natural processes Although evidence of early Life is scarce and often difficult to interpret it appears that life appeared on Earth relatively soon (on the Geologic time scale) after Evolutionary thought, the idea that species change over time has roots in antiquity in the ideas of the Greeks, Romans, Chinese and Muslims theory of transmutation had early origins in the speculations and hypotheses of Erasmus Darwin, and Jean-Baptiste Lamarck. Objections to evolution have been raised ever since various evolutionary ideas came to prominence around the start of the nineteenth century Cladistics is the hierarchical classification of Species based on evolutionary ancestry Ecological genetics is the study of Genetics in the context of the interactions among organisms and between the organisms and their environment Evolutionary developmental biology ( evolution of development or informally evo-devo) is a field of Biology that compares the developmental processes Human evolution, or anthropogenesis, is the part of biological Evolution concerning the emergence of Homo sapiens as a distinct Species Molecular evolution is the process of evolution at the scale of DNA, RNA, and Proteins Molecular evolution emerged as a scientific field in the 1960s as Population genetics is the study of the Allele frequency distribution and change under the influence of the four evolutionary forces Natural selection, Genetic Foundations of modern biology There are five unifying principles Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group Genetic material is used to store the genetic information of an organic life form Mutations can be caused by copying errors in the genetic material during cell division, by exposure to ultraviolet or ionizing radiation, chemical mutagens, or viruses, or can occur deliberately under cellular control during processes such as hypermutation. Cell division is a process by which a cell, called the parent cell divides into two or more cells called daughter cells. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Image talkNew_radiation_symbol_ISO_21482svg for details --> Ionizing radiation In Biology, a mutagen ( Latin, literally origin of change) is a physical or chemical agent that changes the genetic information (usually DNA) A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable Somatic hypermutation (or SHM is a mechanism inside cells that is part of the way the immune system adapts to the new foreign elements which confront it (for example In multicellular organisms, mutations can be subdivided into germ line mutations, which can be passed on to descendants, and somatic mutations, which are not transmitted to descendants in animals. A Germline Mutation is any detectable and heritable variation in the lineage of germ cells. Plants sometimes can transmit somatic mutations to their descendants asexually or sexually (in case when flower buds develop in somatically mutated part of plant). A new mutation that was not inherited from either parent is called a de novo mutation. The source of the mutation is unrelated to the consequence, although the consequences are related to which cells are affected.

Mutations create variations in the gene pool. In Population genetics, a gene pool is the complete set of unique Alleles in a Species or Population. Less favorable (or deleterious) mutations can be reduced in frequency in the gene pool by natural selection, while more favorable (beneficial or advantageous) mutations may accumulate and result in adaptive evolutionary changes. Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of eVolution is the third Album by eLDee, it was due to be released in 2008 For example, a butterfly may produce offspring with new mutations. The majority of these mutations will have no effect; but one might change the color of one of the butterfly's offspring, making it harder (or easier) for predators to see. If this color change is advantageous, the chance of this butterfly surviving and producing its own offspring are a little better, and over time the number of butterflies with this mutation may form a larger percentage of the population.

Neutral mutations are defined as mutations whose effects do not influence the fitness of an individual. The neutral theory of molecular evolution is an influential theory that was introduced with provocative effect by Motoo Kimura in the late 1960s and early 1970s Fitness (often denoted w in Population genetics models is a central concept in evolutionary theory. These can accumulate over time due to genetic drift. In Population genetics, genetic drift is the accumulation of random events that change the makeup of a gene pool slightly but often compound over time It is believed that the overwhelming majority of mutations have no significant effect on an organism's fitness. Also, DNA repair mechanisms are able to mend most changes before they become permanent mutations, and many organisms have mechanisms for eliminating otherwise permanently mutated somatic cells. DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its Genome. Somatic cells are any cells forming the body of an organism as opposed to Germline cells

Mutation is generally accepted by the scientific community as the mechanism upon which natural selection acts, providing the advantageous new traits that survive and multiply in offspring or disadvantageous traits that die out with weaker organisms.

Classification

By effect on structure

Illustrations of five types of chromosomal mutations.

The sequence of a gene can be altered in a number of ways. Gene mutations have varying effects on health depending on where they occur and whether they alter the function of essential proteins. Structurally, mutations can be classified as:

• Small-scale mutations, such those as affecting a small gene in one or a few nucleotides, including:
  • Point mutations, often caused by chemicals or malfunction of DNA replication, exchange a single nucleotide for another^[1]. 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 Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group Most common is the transition that exchanges a purine for a purine (A ↔ G) or a pyrimidine for a pyrimidine, (C ↔ T). Not to be confused with the evolutionary concept of a Transitional fossil. 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 A transition can be caused by nitrous acid, base mis-pairing, or mutagenic base analogs such as 5-bromo-2-deoxyuridine (BrdU). Nitrous acid (molecular formula H[[Nitrogen N]] O 2 is a weak and monobasic Acid known only in Solution and in the form of Nitrite Bromodeoxyuridine (5-bromo-2-deoxyuridine BrdU is a synthetic Nucleoside which is an analogue of Thymidine. Less common is a transversion, which exchanges a purine for a pyrimidine or a pyrimidine for a purine (C/T ↔ A/G). In Molecular biology, transversion refers to the substitution of a Purine for a Pyrimidine or vice versa A point mutation can be reversed by another point mutation, in which the nucleotide is changed back to its original state (true reversion) or by second-site reversion (a complementary mutation elsewhere that results in regained gene functionality). These changes are classified as transitions or transversions^[2]. An example of a transversion is adenine (A) being converted into a cytosine (C). 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 There are also many other examples that can be found. Point mutations that occur within the protein coding region of a gene may be classified into three kinds, depending upon what the erroneous codon codes for:
    • Silent mutations: which code for the same amino acid. 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 Silent mutations are DNA Mutations that do not result in a change to the Amino acid sequence of a Protein. In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this
    • Missense mutations: which code for a different amino acid. In Genetics, a missense mutations (a type of nonsynonymous mutation) is a Point mutation in which a single nucleotide is changed resulting in a Codon
    • Nonsense mutations: which code for a stop and can truncate the protein. In Genetics, a nonsense mutation is a Point mutation in a sequence of DNA that results in a premature Stop codon, or a nonsense Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl
  • Insertions add one or more extra nucleotides into the DNA. Genetic Insertion is the addition of one or more Nucleotide Base pairs into a genetic sequence They are usually caused by transposable elements, or errors during replication of repeating elements (e. Transposons are sequences of DNA that can move around to different positions within the Genome of a single cell, a process called transposition g. AT repeats). Insertions in the coding region of a gene may alter splicing of the mRNA (splice site mutation), or cause a shift in the reading frame (frameshift), both of which can significantly alter the gene product. In Molecular biology, splicing is a modification of an RNA after transcription, in which Introns are removed and Exons are joined Messenger ribonucleic acid ( mRNA) is a molecule of RNA encoding a chemical "blueprint" for a Protein product A splice site mutation is a genetic Mutation that inserts or deletes a number of nucleotides in the specific site at which splicing In Biology, a reading frame is a contiguous and non-overlapping set of three- Nucleotide Codons in DNA or RNA. A frameshift mutation (also called a framing error) is a genetic Mutation caused by Indels ie Insertions can be reverted by excision of the transposable element. Transposons are sequences of DNA that can move around to different positions within the Genome of a single cell, a process called transposition
  • Deletions remove one or more nucleotides from the DNA. In Genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) is a Mutation (a genetic aberration Like insertions, these mutations can alter the reading frame of the gene. In Biology, a reading frame is a contiguous and non-overlapping set of three- Nucleotide Codons in DNA or RNA. They are generally irreversible: though exactly the same sequence might theoretically be restored by an insertion, transposable elements able to revert a very short deletion (say 1-2 bases) in any location are either highly unlikely to exist or do not exist at all. Note that a deletion is not the exact opposite of an insertion: the former is quite random while the latter consists of a specific sequence inserting at locations that are not entirely random or even quite narrowly defined.
• Large-scale mutations in chromosomal structure, including:
  • Amplifications (or gene duplications) leading to multiple copies of all chromosomal regions, increasing the dosage of the genes located within them. A chromosome is an organized structure of DNA and Protein that is found in cells. 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
  • Deletions of large chromosomal regions, leading to loss of the genes within those regions. In Genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) is a Mutation (a genetic aberration
  • Mutations whose effect is to juxtapose previously separate pieces of DNA, potentially bringing together separate genes to form functionally distinct fusion genes (e. A fusion gene is a hybrid gene formed from two previously separate genes g. bcr-abl). Philadelphia chromosome or Philadelphia translocation is a specific chromosomal abnormality that is associated with Chronic myelogenous leukemia (CML These include:
    • Chromosomal translocations: interchange of genetic parts from nonhomologous chromosomes. In Genetics, a chromosome translocation is a Chromosome abnormality caused by rearrangement of parts between nonhomologous Chromosomes.
    • Interstitial deletions: an intra-chromosomal deletion that removes a segment of DNA from a single chromosome, thereby apposing previously distant genes. For example, cells isolated from a human astrocytoma, a type of brain tumor, were found to have a chromosomal deletion removing sequences between the "fused in glioblastoma" (fig) gene and the receptor tyrosine kinase "ros", producing a fusion protein (FIG-ROS). Astrocytomas are primary Central nervous system Tumors that arise primarily in and rarely spread away from the CNS parenchyma contained within the Cranial vault The abnormal FIG-ROS fusion protein has constitutively active kinase activity that causes oncogenic transformation (a transformation from normal cells to cancer cells).
    • Chromosomal inversions: reversing the orientation of a chromosomal segment. An inversion is a Chromosome rearrangement in which a segment of a chromosome is reversed end to end
  • Loss of heterozygosity: loss of one allele, either by a deletion or recombination event, in an organism that previously had two different alleles. Loss of heterozygosity (LOH in a cell represents the loss of normal function of one allele of a gene in which the other allele was already inactivated 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

By effect on function

• Loss-of-function mutations are the result of gene product having less or no function. When the allele has a complete loss of function (null allele) it is often called an amorphic mutation. A null allele is a mutant copy of a gene that completely lacks that gene's normal function 1946 Nobel Prize winner Hermann J Muller (1890-1967 coined the terms amorph hypomorph hypermorph antimorph and neomorph to classify mutations based on their behaviour Phenotypes associated with such mutations are most often recessive. Exceptions are when the organism is haploid, or when the reduced dosage of a normal gene product is not enough for a normal phenotype (this is called haploinsufficiency). "Haplo" redirects here For the fictional character see The Death Gate Cycle. Haploinsufficiency occurs when a Diploid organism only has a single functional copy of a gene (with the other copy inactivated by Mutation) and the single
• Gain-of-function mutations change the gene product such that it gains a new and abnormal function. These mutations usually have dominant phenotypes. Often called a neomorphic mutation. 1946 Nobel Prize winner Hermann J Muller (1890-1967 coined the terms amorph hypomorph hypermorph antimorph and neomorph to classify mutations based on their behaviour
• Dominant negative mutations (also called antimorphic mutations) have an altered gene product that acts antagonistically to the wild-type allele. 1946 Nobel Prize winner Hermann J Muller (1890-1967 coined the terms amorph hypomorph hypermorph antimorph and neomorph to classify mutations based on their behaviour These mutations usually result in an altered molecular function (often inactive) and are characterised by a dominant or semi-dominant phenotype. In humans, Marfan syndrome is an example of a dominant negative mutation occurring in an autosomal dominant disease. Marfan syndrome (or Marfan's syndrome is a genetic disorder of the Connective tissue. In this condition, the defective glycoprotein product of the fibrillin gene (FBN1) antagonizes the product of the normal allele.
• Lethal mutations are mutations that lead the death of the organisms which carry the mutations.

By aspect of phenotype affected

• Morphological mutations usually affect the outward appearance of an individual. Mutations can change the height of a plant or change it from smooth to rough seeds.
• Biochemical mutations result in lesions stopping the enzymatic pathway. Often, morphological mutants are the direct result of a mutation due to the enzymatic pathway.

By inheritance

The human genome contains two copies of each gene- a paternal and a maternal allele.

• Wildtype or Homozygous non-mutated is when neither allele is mutated.
• A Heterozygous mutation is when only one allele is mutated.
• A Homozygous mutation is when both the paternal and maternal alleles have an identical mutation.
• Compound heterozygous mutations or a Genetic compound is when the paternal and maternal alleles have two different mutations. ^[3]

Special classes

• Conditional mutation is a mutation that has wild-type (or less severe) phenotype under certain "permissive" environmental conditions and a mutant phenotype under certain "restrictive" conditions. For example, a temperature-sensitive mutation can cause cell death at high temperature (restrictive condition), but might have no deleterious consequences at a lower temperature (permissive condition).

Causes of mutation

Two classes of mutations are spontaneous mutations (molecular decay) and induced mutations caused by mutagens. In Biology, a mutagen ( Latin, literally origin of change) is a physical or chemical agent that changes the genetic information (usually DNA)

Spontaneous mutations on the molecular level include:

• Tautomerism - A base is changed by the repositioning of a hydrogen atom. Tautomers are Organic compounds that are interconvertible by a Chemical reaction called tautomerization.
• Depurination - Loss of a purine base (A or G). Depurination is a DNA alteration in which the hydrolysis of a Purine base (Adenine or Guanine from the Deoxyribose - Phosphate backbone occurs
• Deamination - Changes a normal base to an atypical base; C → U, (which can be corrected by DNA repair mechanisms), or spontaneous deamination of 5-methycytosine (irreparable), or A → HX (hypoxanthine). Deamination is the removal of an Amine group from a Molecule.
• Transition - A purine changes to another purine, or a pyrimidine to a pyrimidine.
• Transversion - A purine becomes a pyrimidine, or vice versa.

Benzopyrene, the major mutagen in tobacco smoke, in an adduct to DNA. Benzopyrene, C20H12 is a five-ring Polycyclic aromatic hydrocarbon that is Mutagenic and highly Carcinogenic It is a crystalline Tobacco Smoking is the inhalation of smoke from burned dried or cured leaves of the Tobacco plant most often in the form of a Cigarette. Produced from PDB 1JDG.

Induced mutations on the molecular level can be caused by:

• Chemicals
  • Nitrosoguanidine (NTG)
  • Hydroxylamine NH₂OH
  • Base analogs (e. Hydroxylamine is a reactive chemical with formula NH2OH It can be considered a hybrid of Ammonia and Water due to parallels it shares A base analog is a chemical that can substitute for a normal Nucleobase in Nucleic acids A common example would be 5-bromouracil (5BU the abnormal g. BrdU)
  • Simple chemicals (e. Bromodeoxyuridine (5-bromo-2-deoxyuridine BrdU is a synthetic Nucleoside which is an analogue of Thymidine. g. acids)
  • Alkylating agents (e. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are g. N-ethyl-N-nitrosourea (ENU)) These agents can mutate both replicating and non-replicating DNA. ENU, also known as N -ethyl- N -nitrosourea (chemical formula C3H7N3O2 is a highly potent Mutagen. In contrast, a base analog can only mutate the DNA when the analog is incorporated in replicating the DNA. Each of these classes of chemical mutagens has certain effects that then lead to transitions, transversions, or deletions.
  • Methylating agents (e. g. ethyl methanesulfonate (EMS))
  • Polycyclic hydrocarbons (e. Ethyl methanesulfonate (EMS is a Mutagenic Teratogenic and possibly Carcinogenic Organic compound with formula 383 In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. g. benzopyrenes found in internal combustion engine exhaust)
  • DNA intercalating agents (e. Benzopyrene, C20H12 is a five-ring Polycyclic aromatic hydrocarbon that is Mutagenic and highly Carcinogenic It is a crystalline The internal combustion engine is an engine in which the Combustion of Fuel and an Oxidizer (typically air occurs in a confined space called a Exhaust gas is Flue gas which occurs as a result of the Combustion of fuels such as Natural gas, Gasoline /petrol Diesel, Fuel g. ethidium bromide)
  • DNA crosslinker (e. Ethidium bromide (sometimes abbreviated as "EtBr", the abbreviation also confusingly used for Bromoethane) is an intercalating agent g. platinum)
  • Oxidative damage caused by oxygen(O) radicals
• Radiation
  • Ultraviolet radiation (nonionizing radiation) excites electrons to a higher energy level. Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the In Chemistry, radicals (often referred to as free radicals) are atoms molecules or ions with Unpaired electrons on an otherwise Open shell Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays DNA molecules are good absorbers of ultraviolet light, especially that with wavelengths in the 260 to 280 nm range. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a Two nucleotide bases in DNA - cytosine and thymine-are most vulnerable to excitation that can change base-pairing properties. UV light can induce adjacent thymine bases in a DNA strand to pair with each other, as a bulky dimer.
  • Ionizing radiation

DNA has so-called hotspots, where mutations occur up to 100 times more frequently than the normal mutation rate. Image talkNew_radiation_symbol_ISO_21482svg for details --> Ionizing radiation In Genetics, the mutation rate is the chance of a Mutation occurring in an organism or gene in each generation (or in the case of Multicellular organisms A hotspot can be at an unusual base, e. g. , 5-methylcytosine. 5-Methylcytosine is a methylated form of Cytosine in which a Methyl group is attached to carbon 5 altering its structure without altering its base-pairing

Mutation rates also vary across species. In Genetics, the mutation rate is the chance of a Mutation occurring in an organism or gene in each generation (or in the case of Multicellular organisms Evolutionary biologists have theorized that higher mutation rates are beneficial in some situations, because they allow organisms to evolve and therefore adapt more quickly to their environments. For example, repeated exposure of bacteria to antibiotics, and selection of resistant mutants, can result in the selection of bacteria that have a much higher mutation rate than the original population (mutator strains). A mutator genotype is a Genotype with an elevated rate of Mutation.

Nomenclature

Nomenclature of mutations specify the type of mutation and base or amino acid changes.

• Amino acid substitution - (e. g. D111E) The first letter is the one letter code of the wildtype amino acid, the number is the position of the amino acid from the N terminus and the second letter is the one letter code of the amino acid present in the mutation. If the second letter is 'X', any amino acid may replace the wildtype.
• Amino acid deletion - (e. g. ΔF508) The Greek symbol Δ or 'delta' indicates a deletion. The letter refers to the amino acid present in the wildtype and the number is the position from the N terminus of the amino acid were it to be present as in the wildtype.

Types of mutations

Adaptive mutation

Main article: Adaptive mutation

In mainstream biological thought it is held that while mutagenesis is non-random in many ways, the utility of a genetic mutation to the organism in which it occurs does not affect the rate at which it occurs. The central dogma of evolutionary theory is selection from random variation However experimental evidence exists that in some instances the rate of specific mutations arising is greater when they are advantageous to the organism than when they are not.

Back mutation

Back mutation is a change in a nucleotide pair of a point-mutated DNA sequence that restores the original sequence and hence the original phenotype. In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called 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 A DNA sequence or genetic sequence is a succession of letters representing the Primary structure of a real or hypothetical DNA Molecule A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties ^[4]

Frameshift mutation

Main article: Frameshift mutation

A frameshift mutation is a mutation caused by indels, ie. A frameshift mutation (also called a framing error) is a genetic Mutation caused by Indels ie inserts or deletes a number of nucleotides that is not evenly divisible by three from a DNA sequence. 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 Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Due to the triplet nature of gene expression by codons, the insertion or deletion can disrupt the reading frame, or the grouping of the codons, resulting in a completely different translation from the original. 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 genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins In Genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) is a Mutation (a genetic aberration In Biology, a reading frame is a contiguous and non-overlapping set of three- Nucleotide Codons in DNA or RNA. Translation is the first stage of Protein biosynthesis (part of the overall process of Gene expression) The earlier in the sequence the deletion or insertion occurs, the more altered the protein produced is. Genetic Insertion is the addition of one or more Nucleotide Base pairs into a genetic sequence

Missense mutation

Main article: Missense mutation

Missense mutations or nonsynonymous mutations are types of point mutations where a single nucleotide is changed to cause substitution of a different amino acid. In Genetics, a missense mutations (a type of nonsynonymous mutation) is a Point mutation in which a single nucleotide is changed resulting in a Codon 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 In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this This in turn can render the resulting protein nonfunctional. Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl Such mutations are responsible for diseases such as Epidermolysis bullosa, sickle-cell disease, and SOD1 mediated ALS(Boillée 2006, p. Epidermolysis Bullosa ( EB) is a rare Genetic disease characterized by the presence of extremely fragile Skin and recurrent Blister Sickle-cell disease or sickle-cell anaemia (or anemia) is a Blood disorder characterized by Red blood cells that assume an abnormal rigid The enzyme superoxide dismutase ( SOD,) catalyzes the Dismutation of Superoxide into Oxygen and Hydrogen peroxide. Amyotrophic Lateral Sclerosis ( ALS, sometimes called Maladie de Charcot, or in the United States Lou Gehrig's Disease) is a progressive  39).

Neutral mutation

Main article: Neutral mutation

A neutral mutation is a mutation that occurs in an amino acid codon (presumably within an mRNA molecule) which results in the use of a different, but chemically similar, amino acid. In Genetics, a neutral mutation is a mutation that occurs in an amino acid Codon (presumably within an MRNA molecule which results in the use of a different The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins Messenger ribonucleic acid ( mRNA) is a molecule of RNA encoding a chemical "blueprint" for a Protein product In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this This is similar to a silent mutation, where a codon mutation may encode the same amino acid (see Wobble Hypothesis); for example, a change from AUU to AUC will still encode leucine, so no discernible change occurs (a silent mutation). Silent mutations are DNA Mutations that do not result in a change to the Amino acid sequence of a Protein. Leucine (abbreviated as Leu or L) is an α- Amino acid with the Chemical formula HO2CCH(NH2CH2CH(CH32 Silent mutations are DNA Mutations that do not result in a change to the Amino acid sequence of a Protein.

Nonsense mutation

Main article: Nonsense mutation

A nonsense mutation is a point mutation in a sequence of DNA that results in a premature stop codon, or a nonsense codon in the transcribed mRNA, and possibly a truncated, and often nonfunctional protein product. In Genetics, a nonsense mutation is a Point mutation in a sequence of DNA that results in a premature Stop codon, or a nonsense 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 A DNA sequence or genetic sequence is a succession of letters representing the Primary structure of a real or hypothetical DNA Molecule Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known In the Genetic code, a stop codon (or termination codon) is a Nucleotide triplet within Messenger RNA that signals a termination of translation 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 In Mathematics, truncation is the term for limiting the number of digits right of the Decimal point, by discarding the least significant ones Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl

Point mutation

Main article: Point mutation

A point mutation, or substitution, is a type of mutation that causes the replacement of a single base nucleotide with another nucleotide. 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 Often the term point mutation also includes insertions or deletions of a single base pair (which have more of an adverse effect on the synthesized protein due to nucleotides still being read in triplets, but in different frames- a mutation called a frameshift mutation). Genetic Insertion is the addition of one or more Nucleotide Base pairs into a genetic sequence A frameshift mutation (also called a framing error) is a genetic Mutation caused by Indels ie

Silent mutation

Main article: Silent mutation

Silent mutations are DNA mutations that do not result in a change to the amino acid sequence of a protein. Silent mutations are DNA Mutations that do not result in a change to the Amino acid sequence of a Protein. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl They may occur in a non-coding region (outside of a gene or within an intron), or they may occur within an exon in a manner that does not alter the final amino acid sequence. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Introns, derived from the term "intragenic regions" and also called intervening sequence (IVS are DNA regions in a Gene that are not translated into 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 Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this The phrase silent mutation is often used interchangeably with the phrase synonymous mutation; however, synonymous mutations are a subcategory of the former, occurring only within exons. A single nucleotide polymorphism ( SNP, pronounced snip) is a DNA sequence variation occurring when a single Nucleotide - A, T

Harmful mutations

Changes in DNA caused by mutation can cause errors in protein sequence, creating partially or completely non-functional proteins. Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl To function correctly, each cell depends on thousands of proteins to function in the right places at the right times. When a mutation alters a protein that plays a critical role in the body, a medical condition can result. A condition caused by mutations in one or more genes is called a genetic disorder. A genetic disorder is a condition caused by abnormalities in Genes or Chromosomes While some diseases such as Cancer, are due to genetic abnormalities acquired However, only a small percentage of mutations cause genetic disorders; most have no impact on health. For example, some mutations alter a gene's DNA base sequence but don’t change the function of the protein made by the gene. Studies in the fly Drosophila melanogaster suggest that if a mutation does change a protein, this will probably be harmful, with about 70 percent of these mutations having damaging effects, and the remainder being either neutral or weakly beneficial. Drosophila melanogaster (from the Greek for black-bellied dew-lover) is a two-winged insect that belongs to the Diptera, the order ^[5]

If a mutation is present in a germ cell, it can give rise to offspring that carries the mutation in all of its cells. Germ cells are progenitors of the Gametes. These singled out cells move through the gut to the developing Gonads and undergo mitotic proliferation followed This is the case in hereditary diseases. A genetic disorder is a condition caused by abnormalities in Genes or Chromosomes While some diseases such as Cancer, are due to genetic abnormalities acquired On the other hand, a mutation can occur in a somatic cell of an organism. Somatic cells are any cells forming the body of an organism as opposed to Germline cells Such mutations will be present in all descendants of this cell, and certain mutations can cause the cell to become malignant, and thus cause cancer^[6]. Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled

Often, gene mutations that could cause a genetic disorder are repaired by the DNA repair system of the cell. DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its Genome. Each cell has a number of pathways through which enzymes recognize and repair mistakes in DNA. Because DNA can be damaged or mutated in many ways, the process of DNA repair is an important way in which the body protects itself from disease.

Beneficial mutations

A very small percentage of all mutations actually have a positive effect. These mutations lead to new versions of proteins that help an organism and its future generations better adapt to changes in their environment. For example, a specific 32 base pair deletion in human CCR5 (CCR5-Δ32) confers HIV resistance to homozygotes and delays AIDS onset in heterozygotes. In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called CCR5, short for chemokine (C-C motif receptor 5, is a Chemokine receptor. CCR5, short for chemokine (C-C motif receptor 5, is a Chemokine receptor. Human immunodeficiency virus ( HIV) is a Lentivirus (a member of the Retrovirus family that can lead to acquired immunodeficiency syndrome 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 ^[7] The CCR5 mutation is more common in those of European descent. One theory for the etiology of the relatively high frequency of CCR5-Δ32 in the European population is that it conferred resistance to the bubonic plague in mid-14th century Europe. Etiology (alternatively aetiology, aitiology) is the study of causation. Bubonic plague is the best-known manifestation of the bacterial disease plague, caused by the bacterium Yersinia pestis (formerly known as People who had this mutation were able to survive infection; thus, its frequency in the population increased. ^[8] It could also explain why this mutation is not found in Africa where the bubonic plague never reached. Newer theory says the selective pressure on the CCR5 Delta 32 mutation has been caused by smallpox instead of the bubonic plague. Any cause that reduces reproductive success in a proportion of a population potentially exerts Evolutionary pressure or selection pressure. Smallpox is an Infectious disease unique to humans caused by either of two virus variants named Variola major and Variola minor. ^[9]

Other genes influence the development of the body. For example, different alleles in the myostatin pathway influence the strength of the person, since these genes control muscle development. Myostatin (formerly known as Growth differentiation factor 8) is a Growth factor that limits Muscle tissue growth i ^[10]

See also

References

• Leroi A. 2003. Mutants: On the form, varieties & errors of the human body. 1:16-17. Harper Collins 2003
• Maki H. 2002. Origins of spontaneous mutations: specificity and directionality of base-substitution, frameshift, and sequence-substitution mutageneses. Annual Review of Genetics 36:279-303.
• Taggart R. Starr C. Biology The Unity and Diversity of Life: Mutated Genes and Their Protein Products. 14. 4:227. Thompson Brooks/Cole 2006.

Online books

• Chapter 7, The Molecular Basis of Mutation in Modern Genetic Analysis by Anthony J. F. Griffiths, William M. Gelbart, Jeffrey H. Miller and Richard C. Lewontin (1999) published by W. Richard Charles "Dick" Lewontin (born March 29, 1929) is an American Evolutionary biologist H. Freeman and Company ISBN 0-7167-3597-0.
• Chapter 9, Instability of the human genome: mutation and DNA repair in Human Molecular Genetics 2 by Tom Strachan and Andrew P. Read (1999) published by John Wiley & Sons, Inc.
• Genes and Disease from the National Library of Medicine provides descriptions of mutations that cause human diseases. The United States National Library of Medicine ( NLM) operated by the United States federal government, is the world's largest Medical library. For example, a common mutation associated with Huntington disease is an increased number of copies of repeated CGA triplets in the Huntingtin gene. The Huntingtin Gene, also called HD (
• GeneReviews by Roberta A. Pagon, Editor-in-chief is made available by the University of Washington and contains peer-reviewed descriptions of heritable diseases written by experts. See Washington (disambiguation for other uses The University of Washington, founded in 1861, is a public research University For example, BRCA1 and BRCA2 Hereditary Breast/Ovarian Cancer describes mutations in BRCA1 and BRCA2 that are associated with predispositions to cancer. BRCA1 ( Breast cancer 1 early onset is a Human Gene, some mutations of which are associated with a significant increase in the risk of Breast cancer BRCA2 (Breast Cancer Type 2 susceptibility protein is a Human Gene that is involved in the repair of chromosomal

External links

• Central Locus Specific Variation Database at the Institute of Genomics and Integrative Biology
• The mutations chapter of the WikiBooks General Biology textbook
• Examples of Beneficial Mutations
• Gene Therapy Net