Posted by:
Paul Hollander
at Fri Jun 1 16:06:56 2007 [ Email Message ] [ Show All Posts by Paul Hollander ]
>So then are each of these statements accurate?
>
>1. The Sharp Albinos may be Tyrosinase Positive or they may be T-Negative.
Correct.
>2. The Kahl Albinos may be Tyrosinase Positive or they may be T-Negative.
Correct.
>3. The VPI Caramel Albinos may be Tyrosinase Positive or they may be T-Negative.
These would be classified as Tyrosinase positive.
4. The (Fill in the blank) may be Tyrosinase Positive or they may be T-Negative.
All boa constrictors that are lighter than normal but have some black (melanin) pigment are Tyrosinase positive.
Tyrosinase negative albinos are albino because they have a defective tyrosinase enzyme that cannot catalyse the first two steps in the metabolic pathway that leads to melanin. Or they could lack part or all of the gene and not make any tyrosinase at all.
Tyrosinase positive albinos have less melanin than normal because
1. They have a partly defective tyrosinase enzyme that can catalyse the first two steps in the matabolic pathway leading to melanin but produce less product in those steps than normal. It's a bottleneck in the production process.
2. They have a perfectly normal tyrosinase enzyme. A different enzyme catalysing one or more other steps in the melanin biochemical pathway is defective.
3. There is an abnormal gene involved in regulating the amount of tyrosinase produced or the rate at which it is broken down.
4. A gene involved in the maturation of the melanin pigment cell is defective causing the cell to be smaller than normal or an abnormal shape.
5. A defective gene causes the pigment cell to make abnormal pigment granules. Fewer than normal melanin pigment granules, smaller than normal pigment granules, abnormally shaped pigment granules, less dense pigment granules, etc.
6. There are one or more other explanations.
This is why tyrosinase-positive vs. tyrosinase-negative is too simplistic.
Paul Hollander
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RE: More Tyrosinase clarification: - Paul Hollander, Fri Jun 1 16:06:56 2007
