MODIFICATION OF RECOMBINATION FREQUENCY IN DROSOPHILA. II. THE POLYGENIC CONTROL OF CROSSING OVER

Abstract

a previous paper, CHINNICI (1971) reported that the frequency of genetic Iyecombination (crossing over) between the sex linked genes scute (sc) and crossveinless (cv) in Drosophila melanogaster was modified by selection practiced at the levels of the family and the individual. A low line and a high line were established. In the low line, the amount of crossing over between sc-cu was reduced from an original value of 15.4% to 8.5% after 33 generations of selection, while in the high line, the value increased from 15.4% to 22.1%. The response in each line was specific to the sc-cu region, for the amount of crossing over in adjacent regions did not differ between the two lines. Examination of polytene chromosomes eliminated the possibility that these changes were due to inversions, deletions, or duplications detectable at the light microscope level (see CHINNICI 1970,1971 for complete details).