Institute of Agricultural Research Statistics, New Delhi-12
*Present address: Directorate of Research Lebs, West Block 8, New Delhi-22.
Online published on 25 January, 2012.
The effect of incomplete penetrance of a gene on the genetical consequences of positive and negative assortative matings has been studied in this paper. Four models of assortative mating with incomplete penetrance and dominance relationships have been considered. In the first and second models of positive assortative mating with or without dominance, the population attains equilibrium with all the three genotypes present. This is in contrast with the case of complete penetrance where the population becomes homozygous ultimately.
In this case, the distribution of genotypes at equilibrium depends on the initial gene frequencies and the parameter of incomplete penetrance. Irrespective of the initial gene frequency, the inbreeding coefficient at equilibrium decreases as the incomplete penetrance increases. In the third and fourth models of negative assortative mating with or without dominance, the population attains equilibrium, with all the three genotypes present. However, in this case, the initial gene frequencies have no influence on the genotypic frequencies at equilibrium. The heterozygosity of the population at equilibrium under this system is always greater than that of the corresponding random mating population so that the inbreeding coefficient in the population is negative. This is also true with complete penetrance. The effect of incomplete penetrance is to make the inbreeding coefficient of the population at equilibrium less negative.
