GENETIC AND PHENOTYPIC ANALYSIS OF 13 ESSENTIAL GENES IN CYTOLOGICAL INTERVAL 22F1-2 23B1-2 REVEALS NOVEL GENES REQUIRED FOR NEURAL DEVELOPMENT IN DROSOPHILA

In an attempt to identify mutations in the Drosophila synaptotagmin ge ne we have isolated many new rearrangements, point mutations and P ele ment insertions in the 22F1-2; 23B1-2 cytological interval on chromoso me arm 2L. This interval encompasses 13 cytological bands and is shown to contain 13 essential complementation groups, including decapentapl egic, synaptotagmin and Curly. Through chemical and P element mutagene sis we have isolated seven new deletions, which combined with previous ly isolated rearrangements, have allowed us to order most genes in the interval. A genomic walk covering approximately 100 kb within this in terval spans at least five essential genes as identified by chromosoma l aberrations. Preliminary phenotypic characterizations of the mutant phenotype and lethal phase is presented for many mutations. Three loci within this interval are shown to be required for proper neural devel opment. Given that the average number of alleles per complementation g roup is greater than seven, it is very likely that all essential genes within this cytological interval have been identified.