T+/T-
Hi,
Entirely off, but...
T+/T- referrs to whether the tyrosinase gene product
(the enzyme tyrosinase) is present and working or not.
In humans, tyrosinase - albinism results in, well, an albino
human. Amelanistic snakes are T+, that is, their tyrosinase
still works. This is because Tyrosinase catalyzes the first
few steps in the pathway that not only makes eumelanins,
the black, brown, and purple pigments, but also the
pheomelanins, the red and yellow pigments. So the presence
of orange and red in amelanistics means that you're probably
looking at another gene there, something like tyrosinase-related
-protein-2, also called dopachrome tautomerase, which
catalyzes part of the eumelanin synthesis alone. Oddly enough,
though, in mice that's actually the, ah, "slaty" locus, I think,
resulting in gray mice. Mutations in TyrRP-2 in humans don't
seem to do anything at all. Go figure.
A T- boa or python is white with lemon yellow markings, but
on the other hand, nobody's really sure if tyrosinase is
the culprit since so far as I know nobody's done the enzymatic
test on a snake before. And besides, there are all kinds of
partial-loss-of-function mutations in human tyrosinase
("leaky" mutations) which produce varying degrees of, yes,
hypomelanism. Another mutation creates a temperature
sensative enzyme, and still another causes "golden"
albanism in humans. On the other hand, the only common
murine mutation in tyrosinase does cause straight-up tryosinase
-negative albinism. No partial or leaky mutations that I'm
aware of.
Fun n' games.