Chiasma repatterning across a chromosomal hybrid zone between chromosomal races of Mus musculus domesticus

Chiasma number and distribution were analysed in male house mice from a karyotypic hybrid zone between the CD race (2n = 22) and the standard race (2n = 40) located in central Italy. Chiasma repatterning occurs across the transect. The overall trend produces a diminution of chiasmata in the mice with CD chromosomal background. The progressive reduction of chiasmata indicates that genes could pass from one race to another in an asymmetrical way: from metacentric races to the standard population.