Heterozygous inversions and spontaneous male crossing-over in Drosophila ananassae
Experiments were conducted to detect the effects of heterozygous inversions on spontaneous crossing-over in males of Drosophila ananassae by using a second chromosome triple recessive stock and four wild stocks. The karyotypic constitution of all the stocks was known. The occurrence of spontaneous male crossing-over has been observed in all the strains tested though the rate of recombination varies. The results show that crossing-over is completely absent between cu and b genes due to inversion heterozygosity in 2L. The males homozygous in 2L show crossing-over in both regions (cu–b, b–se). The inversion heterozygosity in 2L increases the rate of recombination between b and se genes. Furthermore, two third chromosome inversions, when heterozygous also increase crossing-over in the second chromosome. These results suggest that spontaneous male crossing-over in D. ananassae is affected by heterozygous inversions. Thus the present finding lends support to the earlier suggestion that spontaneous crossing-over in males of D. ananassae is meiotic in origin.Key words: Drosophila ananassae, heterozygous inversions, spontaneous male crossing-over.