Crossing over between closely linked markers spanning the centromere of chromosome 3 inDrosophila melanogaster

Abstract

Recombination in a short genetic interval spanning the proximal region of chromosome 3 was studied in the regions st-in-ri-eg2-Ki-pp. Crossover frequencies in this region varied considerably in different genetic backgrounds; however, in all genotypes, the following observations were made: (1) an excess of multiple recombinant chromosomes indicative of high negative interference, was detected; (2) among the multiple recombi-nants, a positive correlation of simultaneous exchange in the most proximal and shortest adjacent genetic intervals was noted; (3) several classes of reciprocal products were not equally recovered. Three possible explanations for these results are: pre-meiotic exchange, chromatid interference and gene conversion.