Genetic analysis of natural populations of Drosophila melanogaster in Japan. I. Protein polymorphism, lethal gene, sterility gene, inversion polymorphism and linkage disequilibrium.

Abstract

Genetic parameters such as allozyme polymorphisms, lethal frequency, sterility frequency, inversion frequency and linkage disequilibrium were examined simultaneously in 780 2nd and 3rd chromosomes, extracted from 2 natural populations of D. melanogaster. The following results were obtained. The average heterozygosities of 16 allozyme loci were 0.159 in the Akayu (AK) population and 0.181 in the Tanushimaru (TS) population. Little genetic differentiation was observed between populations (I = 0.99). No linkage disequilibrium was observed between allozyme loci. The frequency of the polymorphic inversion In(2L)t was 0.188 and 0.106 in the Akayu and Tanushimaru populations. That of the In(2R)NS was 0.115 and 0.049. That of the In(3L)P was 0.009 and 0.037 and that of the In(3R)P was 0.107 and 0.052. There were no significant linkage disequilibria between inversions. The frequency of lethal carrying 2nd chromosomes was 0.315 and 0.182 in the Akayu and Tanushimaru populations. Those on the 3rd chromosome were found at a frequency of 0.327 and 0.305. The frequencies of sterile 2nd chromosomes in Akayu were 0.147 and 0.127 in males and females, and of the 3rd chromosomes, the respective frequencies were 0.093 and 0.084. Corresponding values for the Tanushimaru population were 0.091 and 0.07, and 0.0 and 0.084, respectively. Significant statistical associations were found between male and female sterility of the same chromosome, indicating pleiotropic gene action. Negative or repulsion linkage disequilibria were found between inversions and allozymes, and between inversions. No evidence of frequency dependent selection with minority advantage was found.