MR CHROMOSOMES IN EURASIAN POPULATIONS OF DROSOPHILA-MELANOGASTER

In natural populations of Drosophila melanogaster, two mutator systems , MR and P-M, are distributed throughout the world. Some evidence show s that these systems can be considered as one. Natural populations of D. melanogaster from Eurasia and North America are fundamentally diffe rent with regard to the P-M system. Comparison of Eurasian and North A merican populations with regard to the MR system was hindered by a lac k of data concerning distribution and frequency of MR factors in Euras ia. In this paper, data on the MR-active chromosomes in natural popula tions of D. melanogaster from Russia and neighboring countries from 19 77 to 1992 are presented. The frequencies of MR chromosomes in Eurasia n populations were shown to be similar to those in North America. Henc e, on a global scale, the MR and P-M mutator systems are expressed ind ependently.