Interaction in Transmission Frequency between the Second and the Third Chromosomes in DROSOPHILA MELANOGASTER

Wild second and third chromosomes from isofemale lines established from wild-inseminated females captured in natural populations of Drosophila melanogaster in Hawaii, New York, North Carolina and Texas were made heterozygous in males with marked second and third chromosomes from a laboratory strain, and the transmission frequencies of the wild second (= k( 2)) and the third (= k(3)) chromosomes from the heterozygous male parents were measured. Based upon the preliminary tests of k( 2), the isofemale lines were classified into two groups; group A included those lines showing average k(2) values considerably smaller than the Mendelian expectation of 0.5, and group B included those lines showing average k(2) values close to 0.5. Effects of the wild second chromosomes on k(2) in group A were suppressed (the average k(2) values increased) by the presence of the wild third chromosomes, whereas the wild second chromosomes in this group, in turn, caused a decrease in k(3) of the wild third chromosomes. The intensities of the observed effects were more or less comparable in their absolute values, and these phenomena do not appear to be due to differential viabilities of zygotes. No such interaction was observed between the wild second and third chromosomes in group B. An extention of the model of the Segregation Distorter system of D. melanogaster, as well as a model based upon the P-M system of hybrid dysgenesis, may explain the observed results.