MUTATIONS AFFECTING INTRACHROMOSOMAL RECO MBINATION AND CONVERSION INA DOUBLE Y(2NS)SC(ME) DROSOPHILA-MELANOGASTER SYSTEM

The effect of mutations in various genes whose products are involved i n chromosome organization on the mutagenesis in a double superunstable y(2ns)SC(me) system was studied. Among these mutations were those in loci zeste, e(y) e(y) 1,2 and 3, responsible for long-distance interac tions in chromosomes, and those in the loci E(z), Su(z), Scm, and Psc, whose protein products take part in chromatin compaction. Many of the mutations studied markedly affect the spectrum and the frequency of m utations in the system, in particular, the frequency of double events. The results suggest that the spatial organization of chromosomal doma ins plays a role in intrachromosomal recombination and gene conversion , since these processes were shown earlier to be dominant in the mutag enesis of a double superunstable system. Some of the mutations under s tudy also modify the phenotypic manifestation of the y(2ns)SC(me) alle le.