Persistent sexual behavior in castrated, recombinant inbred mice

In contrast to other male mice, many hybrid B6D2F1 males continue to mate after being castrated in adulthood. This persistent sexual behavior in the castrated hybrids presumably is based upon heterozygosity that might occur within individual loci or between different loci. Those possibilities were discriminated by studying BXD recombinant inbred mice. In BXD strains, individual loci are homozygous, but heterozygosity has arisen between separate loci. Males in two of six BXD strains persisted in copulating for 5 mo after being castrated. Thus, it is concluded that retention of masculine sexual behavior in castrated mice is a function of heterozygosity between loci.