SELECTION FOR REDUCED CROSSING OVER IN DROSOPHILA MELANOGASTER

Nasr F. Abdullah ¹ and Brian Charlesworth ¹

¹ Department of Genetics, University of Liverpool, Liverpool, L69 3BX, England

Selection was practiced for reducing crossing over between the third chromosome genes Sb and H² of Drosophila melanogaster; the method employed was to select the repulsion double heterozygotes Sb+/+H² every generation. Two replicate selection lines were maintained. After 24 generations of selection, Line 1 showed no significant difference from the control, although the regression of recombination value on generation was significant. In generation 20, Line 2 had a significantly lower recombination value than the control, as well as having a highly significant regression coefficient. No chromosome rearrangements were involved in the response. It was concluded that there was substantial genic variability in the frequency of crossing over between Sb and H² in the base population.