[jjeaff]

The top comment on this post addresses the one gene, one trait evidence. In essence, just because changing one gene mutation fixes the problem, that doesn't mean that only one gene was responsible for the problem in the first place.

"The "one gene = one protein" dogma of molecular biology (expanded: "one trait selectable in breeding experiments = one compact locus of the chromosome") was a priori wrong, but it's taken us decades to undo the damage. We were led astray because there are traits that do map to a single locus, or single mutations that were found to be able to control a trait, which is not the same thing as the trait."