CYTOGENETIC ANALYSIS OF THE CHROMOSOME RE GION CONTAINING RADIOSENSITIVITY GENE IN DROSOPHILA .2. A STUDY OF VITAL LOCI OF 44F-45C REGION OF CHROMOSOME-2

Genetic content of 44F2-3; 4505-6 region of chromosorm 2 characterized by an increased portion of heterochromatin rearrangements in comparis on with other radiation-induced mutations, was studied. Eighteen compl ementation groups of lethal and aviablity reducing mutations were iden tified in 14 consecutive subregions of 44F-3; 4505-6 region using dele tion and complementation analysis. Four additional complementation gro ups were formed only by arrangements of heterochromatin. Location of h eterochromatic aberrations does not coincide with hot spots of intralo cus mutagenesis. Effective lethal period of mutations in 44F2-3; 45C5- 6 region were analyzed. Mutations in 5 loci are lethal at the embryoni c stage, strict lethal mutations of other genes lead to death at the l arval stage. Mutations specifically changing scale and form of certain thorax bristles were identified in haplosensitive Notopleural locus w hich was not characterized earlier. Phenotypes of individuals homozygo us for nonstrictly lethal alleles of vital loci of the region 44F-45C were described.