Population genetics is the study of the allele frequency distribution and change under the influence of the four evolutionary forces: natural selection, genetic drift, mutation and gene flow. Allele frequency is a measure of the relative frequency of an Allele at a genetic place(locus in a Population. Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of 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 biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism In Population genetics, gene flow (also known as gene migration) is the transfer of Alleles of Genes from one Population to another It also takes account of population subdivision and population structure in space. As such, it attempts to explain such phenomena as adaptation and speciation. An adaptation is a characteristic of an Organism that has been favored by Natural selection and Speciation is the Evolutionary process by which new biological Species arise Population genetics was a vital ingredient in the modern evolutionary synthesis, its primary founders were Sewall Wright, J. B. S. Haldane and R. A. Fisher, who also laid the foundations for the related discipline of quantitative genetics. Sewall Green Wright ( December 21, 1889 – March 3, 1988) was an American Geneticist John Burdon Sanderson Haldane FRS ( 5 November 1892 &ndash 1 December 1964) known as Jack (but who used 'J Sir Ronald Aylmer Fisher, FRS ( 17 February 1890 – 29 July 1962) was an English Statistician, Evolutionary Quantitative genetics is the study of continuous traits (such as height or weight and its underlying mechanisms

## Scope and theoretical considerations

Perhaps the most significant "formal" achievement of the modern evolutionary synthesis has been the framework of mathematical population genetics. Indeed some authors (Beatty 1986) would argue that it does define the core of the modern synthesis.

Lewontin (1974) outlined the theoretical task for population genetics. Richard Charles "Dick" Lewontin (born March 29, 1929) is an American Evolutionary biologist He imagined two spaces: a "genotypic space" and a "phenotypic space". The challenge of a complete theory of population genetics is to provide a set of laws that predictably map a population of genotypes (G1) to a phenotype space (P1), where selection takes place, and another set of laws that map the resulting population (P2) back to genotype space (G2) where Mendelian genetics can predict the next generation of genotypes, thus completing the cycle. 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 Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent Even leaving aside for the moment the non-Mendelian aspects revealed by molecular genetics, this is clearly a gargantuan task. Molecular genetics is the field of Biology which studies the structure and function of Genes at a molecular level Visualizing this transformation schematically:

$G_1 \rightarrow^{T_1}P_1 \rightarrow^{T_2}P_2 \rightarrow^{T_3}G_2\rightarrow^{T_4}G_1' \rightarrow \cdots$

(adapted from Lewontin 1974, p. 12). XD

T1 represents the genetic and epigenetic laws, the aspects of functional biology, or development, that transform a genotype into phenotype. In Biology, the term epigenetics refers to changes in Gene expression caused by mechanisms other than changes in the underlying DNA sequence Developmental Biology is the official journal of the Society for Developmental Biology. We will refer to this as the "genotype-phenotype map". The genotype-phenotype distinction is drawn in Genetics. " Genotype " is an organism's full Hereditary information even if not expressed T2 is the transformation due to natural selection, T3 are epigenetic relations that predict genotypes based on the selected phenotypes and finally T4 the rules of Mendelian genetics.

In practice, there are two bodies of evolutionary theory that exist in parallel, traditional population genetics operating in the genotype space and the biometric theory used in plant and animal breeding, operating in phenotype space. Biostatistics (a Portmanteau word made from biology and statistics sometimes referred to as biometry or biometrics) is the application of Statistics Plant breeding is the art and science of changing the genetics of plants for the benefit of humankind This article focuses on selective breeding in domesticated animals The missing part is the mapping between the genotype and phenotype space. This leads to a "sleight of hand" (as Lewontin terms it) whereby variables in the equations of one domain, are considered parameters or constants, where, in a full-treatment they would be transformed themselves by the evolutionary process and are in reality functions of the state variables in the other domain. The "sleight of hand" is assuming that we know this mapping. Proceeding as if we do understand it is enough to analyze many cases of interest. For example, if the phenotype is almost one-to-one with genotype (sickle-cell disease) or the time-scale is sufficiently short, the "constants" can be treated as such; however, there are many situations where it is inaccurate. Sickle-cell disease or sickle-cell anaemia (or anemia) is a Blood disorder characterized by Red blood cells that assume an abnormal rigid

## Population geneticists

The three founders of population genetics were the Britons R.A. Fisher and J.B.S. Haldane and the American Sewall Wright. Sir Ronald Aylmer Fisher, FRS ( 17 February 1890 – 29 July 1962) was an English Statistician, Evolutionary John Burdon Sanderson Haldane FRS ( 5 November 1892 &ndash 1 December 1964) known as Jack (but who used 'J Sewall Green Wright ( December 21, 1889 – March 3, 1988) was an American Geneticist Fisher and Wright had some fundamental disagreements and a controversy about the relative roles of selection and drift continued for much of the century between the Americans and the British. The Frenchman Gustave Malécot was also important early in the development of the discipline. Gustave Malécot ( December 28 1911 &mdash November 1998 was a French Mathematician whose work on Heredity had a strong influence John Maynard Smith was Haldane's pupil, whilst W.D. Hamilton was heavily influenced by the writings of Fisher. Maynard Smith redirects here -- for other uses see Maynard Smith (disambiguation Professor John Maynard Smith, F William Donald Hamilton, FRS ( 1 August 1936 &mdash 7 March 2000) was a British Evolutionary biologist The American George R. Price worked with both Hamilton and Maynard Smith. George R Price (1922 – January 6, 1975) was an American population geneticist. On the American side, Richard Lewontin and the Japanese Motoo Kimura were heavily influenced by Wright. Richard Charles "Dick" Lewontin (born March 29, 1929) is an American Evolutionary biologist Motoo Kimura (木村資生 Kimura Motoo) ( November 13, 1924 - November 13, 1994) was a Japanese biologist best known for introducing

## References

• J. In Genetics, coalescent theory is a retrospective model of population genetics that traces all Alleles of a Gene in a sample from a population to a single Dual Inheritance Theory (DIT also known as Gene-Culture Coevolution, was developed in the late 1970s and early 1980s to explain how Human behavior is a product of Ecological genetics is the study of Genetics in the context of the interactions among organisms and between the organisms and their environment In Population genetics, Ewens' sampling formula, introduced by Warren Ewens, states that under certain conditions (specified below if a random sample of n In Evolutionary biology, fitness landscapes or adaptive landscapes are used to visualize the relationship between Genotypes (or Phenotypes and In Population genetics, the founder effect refers to the loss of genetic variation when a new colony is established by a very small number of individuals from a larger Genetic diversity is a level of Biodiversity that refers to the total number of genetic characteristics in the genetic makeup of a species 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 Genetic erosion is a process whereby an already limited Gene pool of an Endangered species of plant or animal diminishes even more when individuals from the surviving Genetic pollution is undesirable Gene flow into wild populations In Population genetics, a gene pool is the complete set of unique Alleles in a Species or Population. The genotype-phenotype distinction is drawn in Genetics. " Genotype " is an organism's full Hereditary information even if not expressed Habitat fragmentation is a process of environmental change important in Evolution and Conservation biology. Microevolution is the occurrence of small-scale changes in Allele frequencies in a population over a few generations also known as change at or below the 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 In Evolutionary Genetics, Muller's ratchet (named after Hermann Joseph Muller and a mechanical device) is the name given to the process by which Mutational meltdown refers to the process by which a small population accumulates deleterious mutations which leads to loss of fitness and decline of the population A panmictic population is one where all individuals are potential partners A population bottleneck (or genetic bottleneck) is an Evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented Quantitative genetics is the study of continuous traits (such as height or weight and its underlying mechanisms In the context of Evolution, certain traits or Alleles of a Species may be subject to selection Populations with small population size behave differently to larger populations A viral quasispecies is a group of Viruses related by a similar mutation or mutations competing within a highly Mutagenic environment Beatty. "The synthesis and the synthetic theory" in Integrating Scientific Disciplines, edited by W. Bechtel and Nijhoff. Dordrecht, 1986.
• Luigi Luca Cavalli-Sforza. Luigi Luca Cavalli-Sforza (born January 25, 1922) is an Italian population geneticist born in Genoa, who has been a professor at Genes, Peoples, and Languages. North Point Press, 2000.
• Luigi Luca Cavalli-Sforza et al. Luigi Luca Cavalli-Sforza (born January 25, 1922) is an Italian population geneticist born in Genoa, who has been a professor at The History and Geography of Human Genes. Princeton University Press, 1994.
• James F. Crow and Motoo Kimura. James F Crow (born 1916 is Professor Emeritus of Genetics at the University of Wisconsin-Madison. Motoo Kimura (木村資生 Kimura Motoo) ( November 13, 1924 - November 13, 1994) was a Japanese biologist best known for introducing Introduction to Population Genetics Theory. Harper & Row, 1972.
• Warren J Ewens. Warren Ewens, FRS, is an Australian-born professor of Biology at the University of Pennsylvania. Mathematical Population Genetics. Springer-Verlag New York, Inc. , 2004. ISBN 0-387-20191-2
• John H. Gillespie Population Genetics: A Concise Guide, Johns Hopkins Press, 1998. John H Gillespie is an Evolutionary biologist interested in theoretical population genetics and Molecular evolution. ISBN 0-8018-5755-4.
• Richard Halliburton. Introduction to Population Genetics. Prentice Hall, 2004
• Daniel Hartl. Primer of Population Genetics, 3rd edition. Sinauer, 2000. ISBN 0-87893-304-2
• Daniel Hartl and Andrew Clark. Principles of Population Genetics, 3rd edition. Sinauer, 1997. ISBN 0-87893-306-9.
• Richard C. Lewontin. Richard Charles "Dick" Lewontin (born March 29, 1929) is an American Evolutionary biologist The Genetic Basis of Evolutionary Change. Columbia University Press, 1974.
• William B. Provine. Professor William B Provine is an American historian of science, particularly of Evolutionary biology and Population genetics. The Origins of Theoretical Population Genetics. University of Chicago Press. 1971. ISBN 0-226-68464-4.
• Spencer Wells. Spencer Wells (born April 6 1969 in Georgia United States) is a Geneticist and Anthropologist, and an Explorer-in-Residence at the The Journey of Man. Random House, 2002.
• Spencer Wells. Spencer Wells (born April 6 1969 in Georgia United States) is a Geneticist and Anthropologist, and an Explorer-in-Residence at the Deep Ancestry: Inside the Genographic Project. National Geographic Society, 2006.
• Cheung, KH; Osier MV, Kidd JR, Pakstis AJ, Miller PL, Kidd KK (2000). "ALFRED: an allele frequency database for diverse populations and DNA polymorphisms". Nucleic Acids Research 28 (1): 361-3.