P-M HYBRID DYSGENESIS IN A NATURAL-POPULA TION OF DROSOPHILA FROM ALTAI

P-M status of 13 isofemale lines from a natural population of Drosophi la melanogaster from Biisk (Altai) was determined by estimation of fre quency of female gonadal sterility in diagnostic crosses. Content of P -elements in genomes was estimated by in situ hybridization. The avera ge level of P-sensitivity was 97.3%; the average number of P-element c opies per genome was 27.5. This value is significantly higher than est imates of average copy number of the P-element obtained for other popu lations with similar levels of P-sensitivity. No relationship between P-element copy number in the lines and level of their P-sensitivity wa s demonstrated. Based on the data obtained, the Altai population may b e assigned to populations of M-type.