Genetic analysis of X-linked hybrid sterility in the house mouse

Hybrid sterility is a common postzygotic reproduc-tive isolation mechanism that appears in the early stages of speciation of various organisms. Mus mus-culus musculus and Mus musculus domesticus rep-resent two recently separated mouse subspecies particularly suitable for genetic studies of hybrid sterility. Here we show that the introgression of Chr X of M. m. musculus origin (PWD/Ph inbred strain, henceforth PWD) into the genetic background of the C57BL/6J (henceforth B6) inbred strain (predomi-nantly of M. m. domesticus origin) causes male ste-rility. The X-linked hybrid sterility is associated with reduced testes weight, lower sperm count, and mor-phological abnormalities of sperm heads. The analy