Reptile & Amphibian Forums

Can someone explain to me what type of gene this is and what T means? Is it dominant or recessive? What do you breed to get T ?

Thanks,

Mat

np

"T pos. refers to the presense of the enzyme Tyrosinase"*, required for melanin production.
T pos. animals have the ability to produce limited amounts of melanine, as Tyrosinase is present.
T negative animals have no Tyrosinase, therefore no melanine production. This is the "typical" albino that comes to mind.
Melanine is a/the dark skin pigment.
That's the way I understand it.
*Page 171, The Comprehensive Boa Constrictor, Vincent Russo, ECO Herpetological Publishing, 2007.
jsc

What was I thinking?

>Can someone explain to me what type of gene this is and what T means? Is it dominant or recessive? What do you breed to get T?

As already posted, functional tyrosinase is required to produce melanin. A T-negative albino does not have functional tyrosinase and therefore, cannot make melanin. A T-Positive albino has functional tyrosinase but either makes less melanin than a normal snake or cannot make melanin. Either the tyrosinase is less than fully functional or there is some reason not related to tyrosinase.

Nobody has tested either Kahl albino or Sharp albino for tyrosinase activity. If one turns out to be T-negative, the other is likely to be T-positive. Or both could be T-positive.

The reduced melanin in most of the "T-positive albino" boas is caused by recessive mutant genes. There are several types, and each seems to be produced by a different mutant gene. Salmon (AKA hypo) is produced by a dominant mutant gene. It has less melanin than normal, so in my opinion it could be classed as a T-positive albino. Others disagree. YMMV.

Actually, there are so many different ways to make a "T-positive albino" boa that, in my opinion, the term is practically meaningless. I think that each mutant should be given a unique name so that we can discuss them individually. That is the normal practice in genetics. It doesn't make sense to act as if a mutant gene that makes a snake lighter than normal because of a less than normally functional tyrosinase enzyme is like a mutant gene that affects the shape of the pigment granules and a mutant gene that reduces the number of pigment cells.

Paul Hollander