I'm not a genetics guru, but I'm probably closer to it than most posting on this forum.

There is no such thing as "incomplete codominance". There's codominance and incomplete dominance, which have different definitions molecularly, but in both cases the heterozygotes can be distinguished from the two homozygotes. When we lack information about a mutant gene's molecular activity, as is common, we might as well use the two terms synonymously.

As my old genetics prof used to say, the more sensitive the test, the more likely to be able to distinguish the heterozygotes from the homozygotes. Blood typing is extremely sensitive, far more sensitive than eyeballing. In other words, a mutant gene can act as a recessive in one test, a codominant in another test, and produce no detectable difference from normal in a third test.

Dominant, codominant, and recessive are man-made terms, and we use them as if they are as distinct as black and white. But nature is sloppy, and she operates in shades of gray. Then we have to decide which category is the closest fit for our observations. The closest fit does not have to be a perfect fit.

As the eye difference here is pretty subtle and needs testing to see how reliable it is, at this time I agree with Dave Colling. IMO, albino is best classed as a recessive mutant gene, though there is a hint as to which individuals are heterozygotes. More information may change that opinion sometime in the future.

Paul Hollander

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