MUTAGENESIS AND INTERCHROMOSOMAL EFFECT O N CROSSING-OVER IN DROSOPHILA

The possibility of mutational consequences of interchromosomal effect on crossing-over was studied in Drosophila melanogaster females with f our genotypes: (1) structurally normal (control); (2) heterozygous at In(1)-Muller-5 inversion (X chromosome); (3) heterozygous at In(3LR)Cx D inversion (chromosome 3); and (4) heterozygous at both inversions. T he mutational effect was determined through the loss of autosome 2 and formation of arm compounds C(2L) and C(2R). In females with recombina tions, the rate of mutational events did not exceed that of the contro l. It was concluded that interchromosomal effect on crossing-over is o f a regulatory character and distrubs neither recombination itself nor chromosome pairing. Coorientation X-3 leading to the appearance of in tersexes in the progeny occurred in meiosis in females with two invers ions.