What you'd get would be a slightly variant form of the original gene. In other words, this variant form would be an allele of the form already present. Two different alleles still make a gene pair (in herper parlance, are compatible). Two alleles do not work together to make a single version of an enzyme. Each allele produces its own version of the enzyme, and you wind up with a mixture of two slightly different enzymes. If neither version of the enzyme works normally, then you don't get a normal-looking animal. That's the way it works when a himalayan mouse is crossed with an albino mouse. The albino mutant gene in the mouse produces a nonfunctional version of the tyrosinase enzyme. The himalayan mutant gene produces a partly functional version of the tyrosinase enzyme. Crossing an albino and a himalayan produces a mouse that has some pigment but not as much as a homozygous himalayan.

As far as I know, the tyrosinase test is not particularly difficult to do. The hardest part would be getting skin samples from the right boas.

Paul Hollander

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