House mice with metacentric chromosomes in the Middle East

Abstract

The western house mouse (Mus musculus domesticus) is standardly characterised by a karyotype of 40 acrocentric chromosomes. However, within the West European and North African parts of its range there are numerous local races defined by reduced chromosome numbers and metacentric chromosomes (review: NACHMAN and SEARLE 1995). The presence of metacentric chromosomes reflects the fusion of pairs of acrocentric chromosomes at their centromeres (Robertsonian fusions), any metacentrics so formed may evolve into other metacentrics by whole-arm reciprocal translocations (WARTs: HAUFFE and PIALEK 1997). Races with metacentrics may be characterised by a diploid number as low as 22 chromosomes (CAPANNA el al. 1976).