Bar Eye in Drosophila Melanogaster: A Cytological Analysis of Some Mutations and Reverse Mutations.

NUMBER of stocks of Drosophila melanogaster, some of which arose by A changes from wild type to Bar eye, and others by reversions or partial reversions from Bar, double-Bar or double infra-Bar toward wild type, have been accumulated in this laboratory. Most of the stocks originated in this laboratory and were obtained by irradiating males with X-rays, mating them with normal females, and selecting and breeding mutant females from the F1. A few stocks were obtained by workers in other laboratories. The origin of each stock will be given in the descriptions which follow. A cytological analysis of these stocks was made with the following aims: (I) to determine, if possible, the exact relationship of the Bar locus to the bands in the 16A region of the salivary gland chromosome, and ( 2 ) to study the relationship of this locus or band to the loci adjacent to it either in the normal chromosore or by virtue of arrangement. All the stocks examined were obtained as changes from wild type, Bar, double-Bar, or double infra-Bar, and in order to determine correctly the cytological changes associated with changes in phenotype, it was necessary to make a preliminary study of the Bar, double-Bar, and double infra-Bar stocks in this laboratory. The original Bar ( B ) mutant, found by TICE (1914) and established in stock, was found by independent examination of the salivary gland chromosomes by BRIDGES (1936) and by MULLER, PROKOPYEVA, and KOSSIKOV (1936) to have a tandem duplication of the seven bands of the 16A section in the X chromosome, while BRIDGES described double-Bar (BB) as carrying these bands in triplicate. Infra-Bar (B1), obtained by STURTEVANT (1925) from Bar, was found by BRIDGES to have a duplication similar to, if not identical with, that of Bar, while double infra-Bar (BaBz) was associated with a triplication. Subsequently RAPOPORT (1940) has built up, through unequal crossing over, a Bar series with multiplication of the 16A region up to eight times. The Cold Spring Harbor B and BB stocks were found to correspond with BRIDGES’S original analyses. The chromosomes of the BzBi stock were indistinguishable from those of BB.