A gene, Lethal hybrid rescue (Lhr 2-95), which rescues the lethal hybrids between Drosophila melanogaster and D. simulans was found on a second chromosome of D. simulans from a natural population. The cross, melanogaster _??_×simulans _??_, which normally produces only female progeny, resulted in the production of both female and males at an equal frequency when the simulans males carried Lhr. The reciprocal cross, simulans _??_×melanogaster _??_, which ordinarily produces only males, gave rise to about 14% females and 86% males. The cross, XX/Y melanogaster _??_×simulans _??_ carrying Lhr, produced a few percent females, although normal simulans produced only hybrid males. The sex ratio (SR) factor and daughterless (da) gene killed either hybrid males or hybrid females according to their usual actions, showing no specific interactions with the Lhr gene. All hybrids, those rescued by Lhr as well as those produced normally, were completely sterile. Evolutionally implications of Lhr are briefly discussed.
The Genetics Society of Japan