Selective structure of the gene pool: II. The standard method using F-ST statistics

A new approach to the description of the selective structure of the gene po ol that is determined by the type and intensity of selection for individual genes is suggested. Selective pressure is defined based on the heterogenei ty of the interpopulation diversity index F-ST. It is assumed that a signif icant difference between the estimated heterogeneity for the ith gene F-ST( i) and the selectively neutral interpopulation differentiation of the gene pool (F-e) indicate an effect of selection on the ith gene. In order to rev eal such significant differences, empirical F-ST(i) distributions for the h uman gene pools of all parts of the world and five subregions of northeaste rn Eurasia were approximated by different theoretical distributions. It was demonstrated that only beta-distributions yielded a good approximation of the empirical F-ST(i) estimations in all studied gene pools. Based on the b eta-approximations, confidence intervals for F-ST were calculated. These in tervals allowed the genes to be divided into three classes of selective str ucture. Class NEUTRAL comprised genes that were assumed to be selectively n eutral (F-ST(i) approximate to F-e); classes LOWER DIFF and SUPER DIFF comp rised selectively important genes with significantly decreased (F-ST(i) < F -e) and increased (F-ST(i) > F-e) differentiation, respectively. Positions of 80 immunologically important biochemical markers were determined in the selective structure of the gene pools of six regions of the world: Europe, Asia, Africa, Australia, America, and northwestern Eurasia. The suggested m ethod of estimating selective structure can be used if (F) over bar(ST) = F -e, where F-e is a selectively neutral variation of genes. F-e = 4N(e)M(e) + 1)(-1); the main conditions for the use of this method are the following assumptions: (1) the genetic process is stationary and (2) the effective po pulation size (N-e), the migration rate (M-e), and the selection rate (S) a re constant in time and space. If these conditions are not met, a correctio n (numeric resampling) is required.