Competition Involving Dominant Mutants in Experimental Populations of DROSOPHILA MELANOGASTER.

EARLIER papers (MERRELL 1953a, b; MERRELL and UNDERHILL 1956) explored the effects of competition between sex-linked and autosomal recessives and their wild-type alleles in experimental populations of Drosophila melanogaster. FALCONER (1960) has used data from one of these papers (1953b) to show the change in gene frequency under selection of a sex-linked gene, commenting that “there is no well documented case of an autosomal gene.” Actually, there were a few cases (e.g. WIEDEMANN 1936; L‘HERITIER and TEISSIER 1937; NIKORO and GUSSEV 1938; MERRELL and UNDERHILL 1956) but the comment is still, to a large extent, valid. Relatively little experimental work has been done on the adaptive value of specific genes compared to the amount on polygenic traits. Inasmuch as the pioneering theoretical work of FISHER, HALDANE, and WRIGHT on the genetics of populations dealt initially with effects at single loci, this is rather surprising. Furthermore, the number of known cases of genic polymorphism in natural populations (melanism in moths, blood groups in man, burnsi-kandiyohi polymorphism in leopard frogs, etc.) suggests that further work on the adaptive role of individual genes may be of considerable significance. This report deals with the competitive relationship between autosomal and sex-linked dominant genes and their wild-type alleles.