MOLECULAR AND GENETIC DISSECTION OF A REPRODUCTIVE ISOLATION GENE, ZYGOTIC HYBRID RESCUE, OF DROSOPHILA-MELANOGASTER

Hybrids from the cross between males of Drosophila melanogaster and fe males of its sibling species (D. simulans, D. mauritiana, or D. sechel lia) are embryonic lethal when they carry the wild type allele of zygo tic hybrid rescue (zhr) from D. melanogaster. The zhr gene has been ma pped in the proximal region of the X heterochromatin slightly distal t o the proximal breakpoint of In(1)sc(8), the region rich in 1.688 g/cm (3) satellite DNA. Since this satellite DNA does not exist in the sibl ing species, the satellite DNA was considered to be involved in the hy brid lethality. We examined the hypothesis molecular cytogenetically. The results are (1) three Df(1)zhr chromosomes carried this satellite DNA, and (2) hybrids were viable even if the amount of the satellite D NA in hybrids was increased by adding minichromosomes Dp(1;f)1205 and Dp(1;f)1187 into the genome. These results do not support the above hy pothesis.