Mutation induction in the male recombination strains of Drosophila melanogaster

One group of the second chromosome lines isolated from a southern Texas population of Drosophila melanogaster, which has been known to show relatively high frequencies of male recombinations, was found to increase the frequency of sex-linked recessive lethal mutations from a control frequency of 0.18% to 1.63%. The second group, which showed a very much reduced frequency of male recombinations, was found to cause a slight increase to 0.48%, although it was not statistically significant. The first group was also tested for the recessive lethal mutation frequency in the second chromosome; the frequency increased from a control frequency of 0.28% to 2.82%. Mapping of a portion of the sex-linked lethals indicated a distribution along the entire X chromosome, although there was a tendency of clustering towards the tip of the X chromosome. One sex-linked lethal line so far tested was found to be associated with an inversion (approximate breakpoints, 14A-18A). It was suggested that the element causing male recombination might be similar to the hi mutator gene studied earlier by Ives (1950).