Polymorphisms for Lethal Alleles in European Populations of Mus musculus

Abstract
Breeding tests of wild house mice (Mus musculus) from European populations in Denmark and East Germany show that each population contains mice heterozygous for recessive lethal alleles at the T locus (chromosome 17). Two of the lethal alleles found in Europe are indistinguishable from those known to be widespread in North American populations of Mus;one European lethal (from Denmark) represents an hitherto unknown form. The European lethals appear to be maintained as polymorphisms by the same type of gametic selection (sperm transmission ratios of 80 to 99 per cent) previously found in North American t-lethals. Some possible evolutionary histories of lethal polymorphisms in the European subspecies of Mus are discussed.