DEFICIENCY ANALYSIS OF THE TIP OF CHROMOSOME 3R IN DROSOPHILA MELANOGASTER

ABSTRACT Region 98EF-100F in chromosome 3 is interesting for genetic analysis because it contains a number of genes of developmental importance. Although there are no preexisting simple deficiency stocks, this region is amenable to genetic manipulation using other types of rearrangements. In the present investigation we obtained deficiencies by combining the terminal deficiencies formed by segregation of Y;3 translocations with a series of duplications of the tip of 3R, both from Y;3 translocations with different breakpoints and from 3;1 duplications in which the 3R tip is carried as a second arm on the X chromosome. Analysis of such synthetic deficiencies reveals five haplo-abnormal loci in the 98A-100F interval. These include a haplolethal site, a newly described Minute and three previously reported Minute mutations. The newly discovered Minute has been designated M(3)99D and is localized cytologically to bands 99D1-9. The three previously reported Minute loci in the region have been localized more precisely: M(3)1 to bands 99B5-9, M(3)f to bands 99E4-F1 and M(3)g to region 100C-F. In addition, we have been able to obtain synthetic deficiencies uncovering all of the intervals from 99B5 to 100B. These deficiencies will be useful for future genetic and molecular analyses of the genes that map within the right tip of chromosome 3.

Cytological location and lethal interactions of three Minute loci in chromosome 3 of Drosophila melanogaster

SUMMARYUsing seven newly induced duplications, three Minute loci have been located cytologically: M(3)hS 37 in 65F10–11; 66A (a new Minute locus), M(3)i in 67C, and M(3)hy in 68F; 69F. M(3)hS 37 and M(3)hy were previously thought to be allelic because they do not complement for lethality. The finding of Minute mutations with additive or synergistic rather than epistatic interactions makes us suspect that some other Minute mutations have been erroneously called allelic. The involvement of Minute loci in more than one biochemical pathway is discussed in view of the existence of synergistic interactions and of Minute loci without known mutant alleles.

TEMPERATURE-SENSITIVE MUTATIONS IN DROSOPHILA MELANOGASTER. XVI. THE GENETIC PROPERTIES OF SEX-LINKED RECESSIVE COLD-SENSITIVE MUTANTS

Among 3,919 EMS-treated X chromosomes, 25 were retained as cold-sensitive (cs) lethals. That is, more than 20% of flies carrying a cs lethal survive at 22 °C and none at 17 °C and for cs semi-lethals, >30% at 22 °C and <13% at 17 °C. The cs mutations are not randomly distributed, seven being located at the X tip and three being alleles to the right of car. Over half exhibited female sterility or reduced fertility and seven exhibited visible phenotypes characteristic of bobbed and Minute mutations. The possible enrichment for ribosomal protein defects by screening for cold-sensitivity is discussed.