>I guess what I mean to ask is, has anyone ever seen one pattern morph override another?

Yes, I have seen it in pigeons.

The normal pattern on the wings is a slate gray ground color with two parallel black bars. Checker produces a black and gray checker pattern on the wings and is caused by a mutant that is dominant to the normal allele. T-pattern produces wings that are mostly black and is also produced by a mutant gene that is dominant to the normal allele. The T-pattern mutant gene and the checker mutant gene are also alleles. The T-pattern allele is also dominant to the checker allele, so if you have a bird with a T-pattern mutant gene paired with a checker mutant, the bird looks like a bird with two T-pattern mutant genes. As far as I know, no one has found multiple alleles at one locus in the ball python. Yet. A case of multiple alleles has turned up in the corn snake, and another is in the black rat snake.

If you want two dominant mutants that are not alleles, in the pigeon a dominant mutant named spread produces a solid black coloration all over the body. A bird with both spread and checker mutant genes is solid black, like a bird that has the spread mutant gene and lacks the checker mutant gene.

"Epistasis" is the standard genetics noun for a mutant gene that maskes the effects of an independent mutant gene. The verb form is "epistatic", as in "the spread mutant gene is epistatic to checker." The T-pattern mutant is dominant to the checker mutant and not epistatic to the checker mutant because the two mutants are alleles.

Paul Hollander

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