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Population genetics Bio341 Mutation - the ultimate source of all genetic variation Recombination - shuffles existing alleles Selection - different alleles.

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Presentation on theme: "Population genetics Bio341 Mutation - the ultimate source of all genetic variation Recombination - shuffles existing alleles Selection - different alleles."— Presentation transcript:

1 Population genetics Bio341 Mutation - the ultimate source of all genetic variation Recombination - shuffles existing alleles Selection - different alleles and genotypes have different fitness. Frequencies change with time Migration - introduces alleles and genotypes into populations Drift - results in the loss of alleles from populations

2 Mutation and the fluctuation test

3 A population is: a group of individuals of the same species from which the next generation is drawn. (Often included is that members of the same population occupy the same locality and ecological niche.)

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8 Effect of strong selection

9 See: Kent Holsinger’s web site, Univ. Connecticut

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11 Consider a population that is: Haploid Asexual (no recombination) Not subject to any kind of selection

12 Random numbers:1 3 1 4 3 IndividualsIndividuals Generations

13 Random numbers:3 4 3 5 1 IndividualsIndividuals Generations

14 Random numbers:5 3 5 4 4 IndividualsIndividuals Generations

15 Random numbers:5 1 5 1 3 IndividualsIndividuals Generations

16 Random numbers:2 3 1 3 2 IndividualsIndividuals Generations

17 IndividualsIndividuals

18 IndividualsIndividuals Not all individuals leave behind descendants.

19 IndividualsIndividuals Generations Present individuals have a common ancestor.

20 IndividualsIndividuals Generations Present individuals have a common ancestor.

21 IndividualsIndividuals Generations Present individuals have a common ancestor.

22 IndividualsIndividuals Generations Present individuals have a common ancestor.

23 IndividualsIndividuals Generations Present individuals have a common ancestor.

24 For any pair of individuals, what is the chance of a common ancestor in the generation immediately preceding? Answer: 1/N IndividualsIndividuals Generations

25 For any pair of individuals, what is the average time back to the most recent common ancestor? Answer: N generations IndividualsIndividuals Generations

26 For any pair of individuals, what is the average number of mutational events separating them? Answer: 2N where  is the  RATE of mutation per gene (or per nucleotide) per generation. IndividualsIndividuals Generations

27 The effects of various forces on gene frequency (A) 0.0 100.0 Mutation a to A Mutation A to a drift migration Balancing selection Directional selection Selection against heterozygotes


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