[Cytogenetic analysis of the chromosome region containing the Drosophila radiosensitivity gene. II. The vitally important loci of the 44F-45C region of chromosome 2].

Genetic content of 44F2-3; 4505-6 region of chromosome 2 characterized by an increased portion of heterochromatin rearrangements in comparison with other radiation-induced mutations, was studied. Eighteen complementation groups of lethal and viability reducing mutations were identified in 14 consecutive subregions of 44F-3; 4505-6 region using deletion and complementation analysis. Four additional complementation groups were formed only by rearrangements of heterochromatin. Location of heterochromatic aberrations does not coincide with hot spots of intralocus mutagenesis. Effective lethal period of mutations in 44F2-3; 45C5-6 region were analyzed. Mutations in 5 loci are lethal at the embryonic stage, strict lethal mutations of other genes lead to death at the larval stage. Mutations specifically changing scale and form of certain thorax bristles were identified in haplosensitive Notopleural locus which was not characterized earlier. Phenotypes of individuals homozygous for nonstrictly lethal alleles of vital loci of the region 44F-45C were described.