Identification of novel Drosophila meiotic genes recovered in a P-element screen

The segregation of homologous chromosomes from one another is the essence o f meiosis. In many organisms, accurate segregation is ensured by the format ion of chiasmata resulting from crossing over. Drosophila melanogaster fema les use this type of recombination-based system, but they also have mechani sms for segregating achiasmate chromosomes with high fidelity. We describe a P-element mutagenesis and screen in a sensitized genetic background to de tect mutations that impair meiotic chromosome pairing, recombination, or se gregation. Our screen identified two new recombination-deficient mutations: mei-P22, which fully eliminates meiotic recombination, and mei-P26, which decreases meiotic exchange by 70% in a polar. fashion. We also recovered an unusual allele of the ncd gene, whose wild-type product is required for pr oper structure and function of the meiotic spindle. However, the screen yie lded primarily mutants specifically defective in the segregation of achiasm ate chromosomes. Although most of these are alleles of previously undescrib ed genes, five were in the known genes alpha Tubulin67C, CycE, push, and Tr l. The five mutations in known genes produce novel phenotypes for those gen es.