An Extrachromosomal Suppressor of Male Crossing-Over in Drosophila ananassae

Abstract

In Drosophila ananassae, crossing-over in males produces populations of strands having properties comparable to those recovered from females: complementary classes are recovered equally, recombination frequencies are additive, and chromosome interference is positive or absent. On the other hand, the frequency of exchanges in males is generally much lower than in females, and the distribution of exchanges also differs between the sexes (Table 1). The occurrence of crossing-over’ in males is dependent upon a dominant allele located 8 map units to the right of ru, a recessive allele mapped 5 units to the left of ru, and another recessive located in the left arm of chromosome 2. Miscellaneous observations indicate the existence of still undefined loci that regulate the frequency and regional distribution of exchanges in males (Hinton, 1970 and unpublished).