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Suppressors of position-effect variegation and the cdc2Dm gene in Drosophila Melanogaster Clegg, Nigel


Suppressor of Position-Effect-Variegation {Su(var)} mutations in Drosophila melanogaster are believed to identify genes that participate i n the establishment or maintenance of heterochromatic domains. A cytogenetic analysis of region 31 of the Drosophila melanogaster polytene chromosome map was undertaken to clarify the number and position of several previously identified Su(var) mutations. Ten deficiencies were used to divide the 31 region into 15 separate subintervals. Results of this analysis suggest that there is a single Su(var) locus (Suvar(2)1) in the 31A-B region. Two recessive suppressors of position-effect variegation reside in the 31E- 32A region. A fourth locus, Su(var)216, was positioned in region 3IE. Additional mutations were sought throughout the 31 region. In total , one hundred and twenty-one new EMS, gamma-irradiation , and P element induced mutations were tested for complementation and mapped using deficiencies. None of the mutations had a Su(var) phenotype, but 8 alleles failed to complement the lethal phenotype associated with the Su(var)216 chromosome. A P element induced allele of Su(var)216 was cloned and sequenced. The P is adjacent to cdc2Dm, the Drosophila homologue of the fission yeast cdc2 gene. The kinase encoded by cdc2 is required for proper progression through the cell cycle. The lethal phenotype of Su(var)216 can be rescued by an ectopically placed cdc2Dm gene construct; however, the Su(var) phenotypes are not rescued. Deficiency mapping of Su(var)216 with a cdc2Dm gene construct in the genetic background suggests that the Su(var)216 and cdc2Dm mutations may be tightly linked (

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