FURTHER STUDIES ON THE CHROMOSOME MECHANISM RESPONSIBLE FOR UNISEXUAL PROGENIES IN SCIARA. TESTS OF EXCEPTIONAL MALES

Abstract

A preceding paper has shown that XX [female][female] and X[image]X [female][female] are not alike from the standpoint of sex determination. Additional experiments were performed to determine whether X[image]Y [male][male] occurred and if so whether they exhibited the expected type of genetic behavior. A sex-linked mutant character carried in the X chromosome was used, in order to distinguish the ordinary XY type [male] from the exceptional X[image]Y type. Experiments were performed to determine whether the X[image]Y type [male] transmitted the X[image] to his daughters, making them all [female]-producers instead of 50% [male]-producers and 50% ([male]-producers, as would be the case if an ordinary [male] were used. This was found to be the case. In the next generation, using XY [male][male], the progenies were all [female] but 50% of the [female][female] were female producers and 50% male producers as usual. The observations throw some light on the nature of the X[image] chromosome and its relation to X. Perhaps the most significant feature is the fact that X[image] may be substituted for X in both [male][male] and [female][female] without any conspicuous effect on external morphology, viability or fertility of the flies, although it is evident that in nature X[image]Y males and X[image]X[image] females are relatively uncommon.