SEX DETERMINATION IN A SYMMETRICAL AUTOSOMAL MULTILOCUS MODEL

A model of determination of sex by an individual's genotype at n loci is discussed. The parameters that determine the probability that an in dividual is male (or female) depend only on the loci at which the indi vidual is heterozygous, extending the two-gene theory of Feldman et al . (1991, Genetics 129, 297-312). The analysis uses a set indexation te chnique that allows a compact expression of the recombination process, and a transformation of the chromosome frequencies that induces a nat ural subgroup structure on hyperplanes in the frequency simplex. It is shown that the polymorphic equilibria correspond to these subgroups. Conditions are determined under which equilibria that exhibit the even sex ratio are stable. How recombination affects the stability of othe r equilibria, including those with linkage disequilibrium, are also ex plored. (C) 1995 Academic Press, Inc.