A Viable Homozygous Deficiency in Drosophila melanogaster

Abstract

THROUGH combination of fragments of chromosomes from two complicated rearrangements (obtained in my work dealing with the wmt position effect, 1938, in the press), one of which causes a light wmt and the other a very dark wmt eye colour, the first having the break to the left and the other to the right of the w gene, a stock was obtained which had no w gene in its genotype. Since the cytological observations show that the breaks occur near each other, or even at the same point in both the original aberrations, it was concluded that only one gene, namely, the gene white, was deficient. The cytological data agree Well with the phenotypical actions of the w deficiency, which does not differ from a simple w mutation, causing the white eye colour. The cytological observations agree also with the data obtained by numerous authors showing the position of the w gene in the 3C2 region of Bridges' salivary chromosome map. But in the w deficiency combinations the 3C2 band is not thinner than in the normal chromosome.