P-ELEMENT INSERTION ALLELES OF ESSENTIAL GENES ON THE 3RD CHROMOSOME OF DROSOPHILA-MELANOGASTER MUTATIONS AFFECTING EMBRYONIC PNS DEVELOPMENT

To identify novel genes and to isolate tagged mutations in known genes that are required for the development of the peripheral nervous syste m (PNS), we have screened a novel collection of 2460 strains carrying lethal or semilethal P-element insertions on the third chromosome. Mon oclonal antibody 22C10 nas used as a marker to visualize the embryonic PNS. We identified 109 mutant strains that exhibited reproducible phe notypes in the PNS. Cytological and genetic analyses of these strains indicated that 87 mutations affect previously identified genes: tramtr ack (n = 18 alleles), string(n = 15), cyclin A (n = 13), single-minded (n = 13), Delta (n = 9), neuralized (n = 4), pointed (n = 4), extra m acrochaetae (n = 4), prospero (n = 3), tartan (n = 2), and pebble (n = 2). In addition, 13 mutations affect genes that cue identified recent ly in a chemical mutagenesis screen designed to isolate similar mutant s: hearty (n = 3), dorsotonals (n = 2), pavarotti (n = 2), sanpodo (n = 2), dalmatian (n = 1), missensed (n = 1), senseless (n = 1), and sti cky chi (n = 1). The remaining nine mutations define seven novel compl ementation groups. The data presented here demonstrate that this colle ction of P elements will be useful for the identification and cloning of novel genes on the third chromosome, since >70% of mutations identi fied in the screen are caused by the insertion of a P element. A compa rison between this screen and a chemical mutagenesis screen undertaken earlier highlights the complementarity of the two types of genetic sc reens.