Development of interspecific hybrids of Mus.

Artificial insemination has been used to produce interspecific mouse hybrids. Mus musculus x Mus cervicolor cervicolor hybrids failed to complete more than a few cleavage divisions but both M. musculus x M. dunni and M. musculus x M. caroli hybrids completed preimplantation development. These hybrid embryos are heterozygous for various X-linked enzymes and may provide a useful genetic system for studying X-chromosome inactivation during early development. Further development of M. muscuius x M. caroli hybrids was studied: several completed foetal development; a few survived to maturity but none has yet reproduced.