The mitotic delay dependent survival screen in Drosophila identifies new cell cycle genes. V.E. Sollars , D.M. Ruden , M. Alterman. Dept Genetics, Univ Kansas, Lawrence, KS.

   We have used a novel genetic screen to isolate mutations in genes responsible for regulation of the cell cycle and factors involved in its orchestration in Drosophila. This mitotic delay dependent survival screen was used to screen the deficiency stocks, followed by screening of EMS and P-element alleles in those chromosomal regions which tested positive. Genes isolated in this screen fell into three classes including cell cycle genes, maintenance/nutritional genes, and trithorax-group genes. Mutations in twelve genes were isolated including three new loci freshair, bluestreak, and scarecrow. cDNAs were isolated and sequenced for ten of these genes, with sequence information for heat shock protein cognate at 70Cb, heat shock protein 68, and small nuclear RNA U1a presented here. Genes isolated in our screen, as well as zygotic vs. maternal screen results, support the hypothesis that zygotic transcription before the 14th mitotic cycle is an important aspect of development.