| Research Abstract |
Let N(t) = N(t,ωィイD21ィエD2) be the size of population in generation t. We assume that {N(t,ωィイD21ィエD2)}t=0,1,2,…, in a Markov chain of {NィイD21ィエD2, NィイD22ィエD2}, with the transition probability/
P(N(t+1,ωィイD21ィエD2)≠ N(t, ωィイD21ィエD2)|N(t, ωィイD21ィエD2) =NィイD2jィエD2) = qィイD2jィエD2,
P(N(t+1,ωィイD21ィエD2) = N(t, ωィイD21ィエD2)|N(t, ωィイD21ィエD2) =NィイD2jィエD2) = 1 - qィイD2jィエD2,
(1 < NィイD21ィエD2 < NィイD22ィエD2). We consider a locus with two alleles AィイD21ィエD2 and AィイD22ィエD2. Let Z(t,ωィイD21ィエD2,ωィイD22ィエD2) be the number of AィイD21ィエD2 allele in generation t. For given {N(t,ωィイD21ィエD2)}t=0,1,2,…, a Markov chain {Z(t,ωィイD21ィエD2)}t=0,1,2,…, whose probability law is given by P(Z(t+1,ωィイD21ィエD2,ωィイD22ィエD2) = j|Z(t,ωィイD21ィエD2,ωィイD22ィエD2) = I) =(ィイD72N(t+1,ωィイD21ィエD2)(/)jィエD7)j) (ィイD7i(/)2N(t,ωィイD21ィエD2ィエD7)ィイD1jィエD1 (1-ィイD7i(/)2N(t,ωィイD21ィエD2)ィエD7)ィイD12N(t+1+ω1)-JィエD1, 0【less than or equal】I【less than or equal】"N(t,ωィイD21ィエD2), 0【less than or equal】j【less than or equal】2N(t+1,ωィイD21ィエD2), is referred to as a Wright-Fis
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her model with fluctuation of population size.
In population genetics theory, a concept of effective size of population has played and important role. For the above model, we can define two effective sizes. The one is the variance effective size NィイD3(v)(/)eィエD3 and the other is the inbreeding effective size NィイD3(I)(/)eィエD3. In this study, the following properties are shown for the Wright-Fisher model with fluctuation of population size.
1. The variance effective size is the same as the inbreeding effective size NィイD2eィエD2 = NィイD3(v)(/)eィエD3 = NィイD3(I)(/)eィエD3).
2. The explicit form of the effective size NィイD2eィエD2 is determined.
3. The effective size NィイD2eィエD2 is larger (resp. smaller) than the harmonic mean NィイD2HィエD2 of NィイD21ィエD2 and NィイD22ィエD2 if the fluctuation of population size is positively (resp. negatively) autocorrelated. The effective size is the same as the harmonic mean (NィイD2eィエD2 = NィイD2HィエD2) if and only if the fluctuation is uncorrelated.
4. The dependence of qィイD21ィエD2 and qィイD22ィエD2 on the effective size NィイD2eィエD2 is determined.
5. Asymptotic expression for the effective size NィイD2eィエD2 is determined for cases of qィイD21ィエD2, qィイD22ィエD2 → 0 or NィイD21ィエD2, NィイD22ィエD2 → ∞. Less
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