Intra-and interchromosomal effects of heterozygous inversions on recombination in the third chromosome of Drosophila ananassae.

In order to study intra-and interchromosomal effects of heterozygous inversions on recombination in the third chromosome of D.ananassae, experiments were conducted using Stw-pr marker stock and five wild stocks with known karyotypes. The stocks used were homozygous for standard or inverted gene sequence in 2L, 3L, and 3R. Recombination was investigated in both sexes. There was complete absence of crossing-over in males in all the experiments which appeared to be the characteristic of marker stock as spontaneous male crossing-over was reported earlier with the same wild stocks when the second chromosome markers were used. Based on the data of karyotypically homozygous F1 females, the map distance between stw-pr was 36.55 map units. The heterozygosity due to a lengthy inversion in 2L increased the level of crossing-over between stw-pr genes of the third chromosome indicating interchromosomal effect. There was a considerable reduction in the rate of recombination between the same markers due to inversion heterozygosity in 3R indicating intrachromosomal effect. However, 3L inversion heterozygosity had no effect on crossover rate. These results provide evidence for intra-and interchromosomal effects of inversions on crossing-over in the third chromosome of D. ananassae.