X-ray-and TEM-induced mitotic recombination in Drosophila melanogaster: Unequal and sister-strand recombination

Summary

Twin mosaic spots of dark-apricot and light-apricot ommatidia were found in the eyes of w ^a/w^a females, of w ^a males, of females homozygous for In(1)sc ⁴, w^a and of attached-X females homozygous for w ^a. The flies were raised from larvae which had been treated with 1630 R of X-rays at the age of 48–52 hours. An additional group of w ^a/w^a males came from larvae that had been fed with triethylene melamine (TEM) at the age of 22–24 hours.

The twin spots apparently were the result of induced unequal mitotic recombination, i.e. from unequal sister-strand recombination in the males and from unequal sister-strand recombination as well as, possibly, unequal recombination between homologous strands in the females. That is, a duplication resulted in w ^aDp w^a/w^a dark-apricot ommatidia and the corresponding deficiency in an adjacent area of w ^a/Df w^a light-apricot ommatidia.

In an additional experiment sister-strand, mitotic recombination in the ring-X chromosome of ring-X/rod-X females heterozygous for w and w ^co is believed to be the cause for X-ray induced single mosaic spots that show the phenotype of the rod-X marker.