_{g}= (1/2)N + [1 − (1/2)N]F

_{g−1}and this is called the

*index of fixation*. Its complement is the

*panmictic index*(P

_{g}) that represents the average non-inbred fraction of the population:

*A*or

*a*alleles is Fp

_{AA}and Fq

_{aa}, respectively. Also, the probability of two alleles of a locus being non-identical by descent is 1–F, and the proportions of

*AA*,

*Aa*, and

*aa*are p

^{2}, 2pq, and q

^{2}(according to the Hardy-Weinberg theorem). Because the population will have both inbred and non-inbred components, its genetic structure will be:

When a population is completely inbred, only homozygotes are found. There may be a change in genotypes but may not be a change in allelic frequencies if both alleles have equal fitness. The change may actually be from *AA* + *2Aa* + *aa* → *AA* + *AA* + *aa* + *aa*, i.e., mathematically it is the same. The ultimate probability of fixation \({\rm{P}}_{\rm{f}} = {{1 - e^{ - N_e } sp} \over {1 - e^{ - N_e } s}}\) may be estimated also on the basis of the *initial frequency of the gene* (= p), the *selection advantage* (= s) and the *effective population size* (N_{e}). [The base of the natural logarithm = *e ≈* 2.718]. inbreeding, panmixis, inbreeding rate, Hardy-Weinberg theorem, mutation neutral, mutation beneficial, hybrid vigor; Whitlock MC 2003 Genetics 164:767.