A polygenic basis of hybrid sterility may give rise to spurious localizations of major sterility factors.

A simple model is presented to illustrate how an underlying generalized polygenic basis of hybrid sterility is expected to lead to spurious localizations of factors with major effects, when a conventional experiment of recombination mapping is carried out. The model shows that a major gene will be detected at roughly the same distance from each of the chromosome markers used in the experiment. These expectations are contrasted with the results from several experiments on hybrid male sterility in Drosophila, which claimed to have mapped single sterility factors. It is concluded that, except for one report, all the evidence presented so far on the genetic basis of hybrid male sterility in Drosophila is in fact compatible with the generalized polygenic model.