Flashcards in Lecture 19 Deck (19):
1
F
 Inbreeding coefficient
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H
 Heterozygosity
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N
 Population size, the number of breeding intividuals
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t
 Generation time
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Autozygous (F):
 The probability of that any two randomly chosen alleles in a population are identical by descent
 A1A1 or A2A2 from the same A1 or A2
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Allozygous (1  F):
 The probability of that any two randomly chosen aleles in a population are NOT identical by descent
 A1A1 or A2A2 from different A1 or A2
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Generational increase in frequency of homozygotes in a selfing population:
 G0 AA 0, Aa 1, aa 0
 G1 AA 1/4, Aa 1/2, aa 1/4
 G2 AA3/8, Aa1/4, aa 2/8
 G AA 1/2, AA 0, aa 0
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Effects of inbreeding:
 Decrease in heterozygosity
 Increase in homozygosity
 Allele frequencies do not change
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Hardy Weinburg Equilibrium:
 A1A1 = 2pq 2pqF
 p + q = 1
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Homozygous:
A1A1 = p squared (1  F) + pF
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Heterozygous:
A1A2 = 2pq (1F)
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Calculating F from observed genotype frequencies:
A1A2 = 2pq (1F)
 Allele frequency of A1
 Allele frequency of A2
 Observed heterozygosity
 F =
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Reduction in heterozygosity is a convenient measure of the effect of inbreeding in a population:
 F = (Hexp  Hobs) / Hexp
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Can we predict how fast F increase and H decrease over time in a finite population?
 Yes

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Ft = 1  [11/2N] t the power t (1Fo)
F = Level of inbreeding in generation t
N = Population size
t = Generation
o = Level of inbreeding in the base population
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Ht = Ho [11/2N] to the power t
Ht = heterozygosity in generation t
Ho = Heterozygosity in the base population
t = generation
N = population size
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From generation t to t+1, there are 2 ways to get alleles IBD
 1/2N
 Probability of an individual receiving two copies of the same allele (new inbreeding)
OR
 [11/2N] Ft
 Probability of an individual receiving copies of two different alleles from generation t, but those alleles are identical by descent from generation t1 (previous inbreeding)
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Increase in inbreeding (F) over time in finite populations:
Ft = 1 [1  1/2N]to the power t
 F will increase over time as a function of population size (N)
 When N is large, F increases slowly over time
 When N is small, F increases rapidly over time
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