Trouble is, a tyrosinase positive albino animal does not have to have any melanin. And some tyrosinase positive animals with some melanin have abnormal tyrosinase. Both cats and mice have tyrosinase negative albino mutants. The Siamese cat is light colored because it has an abnormal tyrosinase enzyme that can produce SOME melanin. This is an allele of the tyrosinase negative mutant gene. The mouse has several mutants that produce abnormal, yet partly functional, tyrosinase, and all are alleles of the tyrosinase negative albino mutant.

It's brutal facts like these that slay the tyrosinase positive/tyrosinase negative dichotomy.

Paul Hollander

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