THE HSR ON CHROMOSOME-1 OF THE HOUSE MOUSE, MUS-DOMESTICUS - DISTRIBUTION AND FREQUENCY IN SWITZERLAND

A total of 357 house mice (Mus domesticus) from 83 localities uniforml y distributed throughout Switzerland were screened for the presence of a homogenously staining region (HSR) on chromosome 1. Altogether 47 m ice from 11 localities were HSR/+ or HSR/HSR. One sample of 11 individ uals all had an HSR/HSR karyotype. Almost all mice with the variant we re collected from the Rhone valley (HSR frequency: 61%) and Val Bregag lia (HSR frequency: 81%). For samples from most of the area of Switzer land, the HSR was absent. There was no strong association between the geographic distribution of the HSR and the areas of occurrence of meta centrics. However, at Chiggiogna the HSR was found on Rb (1.3). Possib le explanations for the HSR polymorphism are discussed.