Basic concepts of population genetics - Bioversity International

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Gene and allele A gene is the basic physical and functional unit of heredity, passing information from one generation to the next An allele is any of the alternative forms of a gene that can exist at a single locus Copyright: IPGRI and Cornell University, 2003 Population genetics 6 Not all of a DNA sequence is made up of genes. Genes are those sections of DNA that have a known function. They include a transcribed section and a regulatory element that allows its transcription. The existence of genes is deduced by observing the segregation of variants in the progeny of crosses, whether naturally or artificially produced. This observation was the basis on which Gregor Mendel defined the laws of inheritance at the end of the 19 th century. Genes may have two or more alleles. Indeed, a gene may have so many alleles as to constitute an allelic series for that gene. Alleles belonging to a series may show different patterns of dominance to each other. For example, an allele may show a dominant effect, which means that it expresses its phenotype, even if accompanied by a recessive allele. A recessive allele is one where its phenotype is not expressed in an heterozygous individual. If an allele is codominant, its phenotypic effect will be intermediate in the heterozygote relative to the effect of an homozygous dominant and that of an homozygous recessive. 6
Genotype is … The description of the complete set of genes that an individual inherits from its parents The genotype of an individual remains unchanged throughout its life, regardless of the environment surrounding and affecting it Copyright: IPGRI and Cornell University, 2003 Population genetics 7 The term ‘gene’ generally refers to the physical entity that is transmitted from parents to offspring during the reproductive process that influences hereditary traits. An individual’s genotype, then, is the sum of all genes inherited from its parents. Genes determine the composition of proteins and also influence external traits and behaviour. 7
Page 1 and 2: Genetic diversity analysis with mol
Page 3 and 4: Definitions: Population genetics T
Page 5: Phenotypic variation Pink Pale crea
Page 9 and 10: What is polymorphism? ‘Presence
Page 11 and 12: Population structure Three levels o
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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Basic concepts of population genetics - Bioversity International

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