A LARGE ACROCENTRIC CHROMOSOME IN THE FIRST PAIR OF AUTOSOMES IN NATURAL-POPULATIONS OF MUS-MUSCULUS, LINNE 1758

In this study, polymorphism of chromosomes was examined in natural pop ulations of Mus musculus. The investigations were conducted in 5 diffe rent localities (Sevarice, Glusci, Lipolist, Bogatic, Sremska Mitrovic a) in North-West Serbia, around, the rivers Sava and Danube. Besides t he frequent finding of Robertsonian type of chromosomal polymorphism, the presence of one large acrocentric chromosome in the first pair of autosome, unusual for the mouse karyotype, was observed in a large num ber of investigated animals. With appropriate cytogenetical methods, i t was established that the altered chromosome had two additional inser tions, located in regions 1C5 and 1R. From the results obtained for mo use karyotype rests and data from the literature, it could be conclude d that the observed acrocentric chromosome resulted as an adaptation o f mice to an increased quantity of environmental, agrichemical and ind ustrial pollutants in the investigated localities.