>>Tyrosinase-positive - an albino not able to synthesize melanin, but capable of synthesizing tyrosinase, which results in lavender-brown or a greenish tint to it skin color. Also referred to as T-positive



>>Tyrosinase-positive - This is what I feel that the "Extremes" could or should be called.



>That's an interesting explanation. If your definition is a widely-accepted and accurate one (not questioning you, merely expressing my own ignorance) then it's a well thought out argument.



IMHO, while those definitions may be widely accepted among herpers, they are not well though out.



First, when Bern Bechtel started using "tyrosinase positive" albino, he used it as a unique name for a particular mutant gene in the black rat snake. That is considerably different from using is as a category including a variety of mutant genes.



If a snake is not normally colored, I would like to know why. Tyrosinase negative isn't too bad, because it tells me that there is a malfunctioning tyrosinase enzyme. Tyrosinase positive means an unknown something other than the tyrosinase enzyme is malfunctioning. And it is very annoying to mate Joe's "tyrosinase positive" snake to Bill's "tyrosinase positive" snake and get a litter of normal babies. There are so many things other than tyrosinase that might be malfunctioning that lumping them all together under "tyrosinase positive" is highly simplistic.



Another problem. "Tyrosinase negative" implies to me a lack of tyrosinase enzyme. And in the lab mouse, there are over a dozen mutant alleles of the albino mutant, which is the mouse's tyrosinase negative mutant gene. Some of those are caused by deletions of the entire gene from the chromosome. The albino mutant produces a nonfunctional tyrosinase enzyme. Other alleles produce partially functional tyrosinase, which produce various shades of brown which are all lighter than normal but not pure white with pink eyes.



And testing is essential to a tyrosinase positive vs tyrosinase negative dichotomy, even if the dichotomy was well thought out. Has there been such testing in the Honduran milk snake?



Paul Hollander

[ Show Entire Thread ]