Linkage-dependent gene flow in a house mouse chromosomal hybrid zone.

In the alpine valley of Valtellina there are two Robertsonian chromosomal races of house mouse, the Poschiavo (POS: 2n = 24-26) characterized by metacentric 8.12 and acrocentrics 2 and 10 and the Upper Valtellina (UV: 2n = 22-24) characterized by metacentrics 2.8 and 10.