This is not a joke.

You can have a wild type/normal looking creature that is heterozygous for a dominant or codominant mutant gene. For example, in humans, there is a dominant mutant gene that causes the possessor to have more than five fingers/toes on each hand/foot. Some humans have the gene without having extra fingers/toes. Such humans can give the gene to their babies, who may show the effect of the gene.

The usual explanation is that other genes and/or environmental factors prevent the gene from visibly expressing itself.

"Incomplete penetrance" is the technical term for such cases. It is not limited to dominant and codominant mutant genes. The term also applies to recessive mutant genes when they are homozygous but are not expressed.

However, in practical terms, there are a lot of crooks out there making bogus claims. So I would not buy such a snake.

Paul Hollander

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