A Third Locus (lxd) Affecting Xanthine Dehydrogenase in Drosophila Melanogaster.

WO genes which affect xanthine dehydrogenase in Drosophila melanogaster Tare already known. These are maroon-like (ma-1) on the X chromosome, and rosy ( r y ) on the third chromosome. The phenotype of both of these mutants is a dark red-brown eye color. When either of these genes is homozygous, the mutant flies have no detectable amounts of xanthine dehydrogenase (FORREST, GLASSMAN, and MITCHELL 1956; GLASSMAN and MITCHELL 1959). In such flies, the substrates of the enzyme accumulate and the products are absent (HADORN and SCHWINK 1956; MITCHELL, GLASSMAN, and HADORN 1958). In vitro complementation between extracts of ma-Z and ry has been reported (GLASSMAN 1962a). Recently, we have found a strain of flies having only about 25 percent of the xanthine dehydrogenase activity found in standard wild-type strains. These flies with low enzyme activity have wild-type eye color and wild-type amounts of the substrates and products of xanthine dehydrogenase. This paper is concerned with the genetic analysis of this strain (designated Low).