Loci affecting male fertility in hybrids between Mus macedonicus and C57BL/6.

Male F1 hybrids between inbred strains and Mus macedonicus have very small testes and are sterile. Cytological analysis of testes shows very few meioses. To determine the genetic basis for this sterility, (C57BL/6J x Mus macedonics) F1 females were mated to males from C57BL/10J.