Essential Genetics 6th Edition by Daniel Hartl

تمرين 4

The autosomal gene rosy (ry) in Drosophila is the structural gene for the enzyme xanthine dehydrogenase (XDH), which is necessary for wildtype eye pigmentation. Flies of genotype ry/ry lack XDH activity and have rosy eyes. The X-linked gene maroonlike (mal) is also necessary for XDH activity, and
that have wildtype eye color, even though their genotypes would imply that they should have rosy eyes. Suggest an explanation.