Determining if one gene or two seperates phenotypes

[MacCarth]

Hey everyone, I'm currently trying to find out if one gene or two genes separates eye color in Drosophila melanogaster. Both of the eye color genes are mutant (one is "white" (w) and the other is "scarlet" (st)). I know that the while gene is located on the "X" chromosome and the scarlet gene is located on the 3rd chromosome, but how do I know if the genes are acting independently of one another or not? Additionally, if they DID work together, what kind of results would I expect?

Right now I'm stumped and I'd really appreciate it if someone could help a genetics novice out.

[zami'87.]

Check this http://flybase.org/
Results will be different if products of genes are on the same biochemical pathway than if they’re on different pathway.
For example in epistasis one defective enzyme1(earlier on pathway) masks other functional enzyme2..because they both need to be functional so that you can detect some characteristic. If enzymes are on different pathways you’ll get four phenotypes...for each gene one,and one when both genes(products actually) are functional,and one when none is functional.