Differential response to gene dosage experiments involving the two loci which control xanthine dehydrogenase ofDrosophila melanogaster

Summary Assays of xanthine dehydrogenase in flies heterozygous forry indicate that these heterozygotes have about 50–70% of the activity of normal. Thus, thery mutants appear to be similar to other genes in which the heterozygote has lower enzyme activity than the homozygous wild-type. On the other hand, the data obtained fromma-l ⁺ /ma-l heterozygotes indicate no dosage response toma-l. This is substantiated by the insertion ofma-l ⁺-bearing chromosomal fragments into various diploid combinations ofma-l ⁺ andma-l. The results demonstrate that one dose ofma-l ⁺ produces normal amounts of xanthine dehydrogenase activity, even in the presence ofma-l.With 1 Figure in the TextThis work was supported by a grant (RG-8202) from the National Institutes of Health.