Basic concepts of population genetics - Bioversity International

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A population is … Ecologically: A group of individuals of the same species living within a restricted geographical area that allows any two individuals to interbreed Genetically: A group of individuals who share a common gene pool and have the potential to interbreed Copyright: IPGRI and Cornell University, 2003 Population genetics 10 Populations are extremely complex entities. In population genetics, the focus is on the local interbreeding unit of a larger population because changes in allele frequencies occur within such limited units and may result in the evolution of adaptive traits. These local interbreeding units are usually called local populations, subpopulations or simply populations. Normally, in a population, members of a species are unevenly distributed. Subdivision of populations are often due to accidents in the environment where they are present. In principle, population size is not infinitely large and does not remain constant. 10
Population structure Three levels of population structure are identified: Individual organisms Subpopulations Total population Copyright: IPGRI and Cornell University, 2003 Population genetics 11 A population may be considered as a single unit. However, in many species and circumstances, populations are subdivided in smaller units. Such subdivision may be the result of ecological (habitats are not continuous) or behavioural factors (conscious or unconscious relocation). If a population is subdivided, the genetic links among its parts may differ, depending on the real degree of gene flow taking place. A population is considered structured if (1) genetic drift is occurring in some of its subpopulations, (2) migration does not happen uniformly throughout the population, or (3) mating is not random throughout the population. A population’s structure affects the extent of genetic variation and its patterns of distribution. See the following slides and the Glossary for more details on these new concepts (e.g. gene flow, migration). 11
Page 1 and 2: Genetic diversity analysis with mol
Page 3 and 4: Definitions: Population genetics T
Page 5 and 6: Phenotypic variation Pink Pale crea
Page 7 and 8: Genotype is … The description of
Page 9: What is polymorphism? ‘Presence
Page 13 and 14: Allele frequency Allele frequency
Page 15 and 16: Genotype frequency This is the fre
Page 17 and 18: Demonstrating the H-W principle Gen
Page 19 and 20: The chi-square test This hypothesi
Page 21 and 22: Calculating allele frequencies: Exa
Page 23 and 24: Locus A B D … with a codominant m
Page 25 and 26: Locus A Locus B Locus D … with a
Page 27 and 28: ... with a codominant gene having m
Page 29 and 30: Random mating Mating that takes pl
Page 31 and 32: Inbreeding coefficient It compares
Page 33 and 34: Forces shaping genetic diversity M
Page 35 and 36: Migration It is the movement of in
Page 37 and 38: Selection It is the inherited abili
Page 39 and 40: Effective population size Ne is th
Page 41 and 42: Consequences … (continued) A bot
Page 43 and 44: Appendix 1 Copyright: IPGRI and Cor
Page 45 and 46: By now you should know … The bas
Page 47:
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