# T+ vs T-



## brick

could someone explain mto me the difference between T+ and T- in the albino genes? i a bit confused about it all

cheers
dave


----------



## Akua_Ko_Nalu

T+ and T- stand for Tyrosinase Positive and Negative.

Which essentially mean Tyrosinase is present or not.

I'm not entirely sure, but Tyrosinase is used to synthesize Melanin, therefore T- Animals, such as White Albino Reticulated Pythons and Albino Ball Pythons, will show no visual signs of black anywhere.

T+ animals, such as Caramel Albino Ball Pythons and T+ Albino Blood Pythons, will have the Black areas replaced by washed over colouration.

Someone should be able to explain it better!


----------



## Ssthisto

Albinism is the result of the cells failing to produce melanin as normal.

An animal that cannot produce Melanin OR Tyrosinase tends to have white "blank" areas in place of the black pigment that would normally be on the animal (like Albino Burms, albino royals and so on.) 

An animal that can produce Tyrosinase (which is a chemical USED to produce Melanin but is not itself melanin) will have tinted - brown, pinkish, golden, caramel - areas in place of the normal black.

I assume that leopard geckos are somewhat dependent on temperature to produce Tyrosinase - but that all albino leos are T+.

In all practical terms, however.... T+ and T- don't mean anything of real use to a herper


----------



## Akua_Ko_Nalu

I was kinda right, but Ssthisto as always, has a great way of explaining genetics.


----------



## paulh

Most herpers are more or less confused about the difference between tyrosinase negative and tyrosinase positive albinos. 

A journey of a thousand miles begins with a single step. The journey along the biosynthetic pathway from tyrosine to melanin begins with a single step, too, but it does not end with the first step. Many steps are required to make melanin. Normal tyrosinase catalyses the first two steps in that pathway. A T-neg albino has either malfunctioning tyrosinase or no tyrosinase so cannot make melanin. Result: an animal without melanin.

The test for T-neg albinism is to make a solution containing the third chemical in the melanin biosynthetic pathway and to put a bit of albino skin in the solution. This skips the steps requiring tyrosinase. If the skin develops melanin, then tyrosinase is the problem. The animal is a T-neg albino. If the skin does not develop melanin, then the problem is not the tyrosinase. And the animal is a T-positive albino.

There are many causes for T-positive albinism, too many to go into here.

The only way to distinguish between T-neg and T-pos albinos is by the test I discribed above. This test has not been done on most albino reptiles. It has not been done on either the Kahl or Sharp albino boa constrictor, it hasn't been done on the albino ball python, and, as far as I know, it hasn't been done on any albino gecko.

Another problem is that there has been a tendency to call reptiles without visible melanin T-neg albinos and reptiles with a little visible melanin T-positive albinos. It doesn't work that way. There can be T-positive albinos with no visible melanin. In other words, there is no way to just look at an animal and say that it is T-neg or T-pos albino. 

Without the test, an albino without visible melanin can be either a T-neg or a T-pos albino. An albino with some visible melanin must have working tyrosinase. But is it an albino if it has some visible melanin? The situation is a mess. :censor:

Until tests are done, about all we can do is treat T-neg albino and T-pos albino as names with no connection to biochemical reality.


----------



## brick

cheers for that response, some of you seem to know a lot about the subject. Yeah it has confused me a lot, and then where do amelanstic reptiles come into the picture. From my few years in as a herper it doesnt seem that there are way to many names for reptiles morphs etc, that may not be exactly correct, or because two animals looking the same were produced by different people, they get different names etc etc etc

can any of you guys give me a link, to a beginners guide to genetics in reptiles, i think i really need to start at the beginning to understand it more.

cheers
dave


----------



## Daveyboy

New England Reptile Distributors, designer Ball Pythons, Reticulated Pythons, and much more!

intro in to genetics from NERD.
They also cover simple recessive, double recessive and co-dominant/dominat genetics.

Hope it helps


----------



## paulh

Learn standard genetics first. Trying to learn genetics from the NERD web site will mess up your mind so badly that you may never get genetics straight.

Serpwidgets' genetics tutorial is good as far at it goes. It is primarily aimed at corn snakes and does not try to cover dominant and codominant mutant genes.
Genetics

Genetics Home Reference has good stuff about the physical make up of cells, chromosomes, and genes and how they work.
Handbook - Genetics Home Reference

The Blue Genes web page -- a genetics unit for high schoolers. Not perfect but better than the herper genetics pages you'd find.
Main Menu

Wilmer Miller's Survey of Genetics is large so you need a fast connection. But if you have one, it is listed (in four parts) on the Contents page of his web site:
Wilmer Jay Miller's web site

Genetics for Herpers
Genetics For Herpers

Appying the principles to other species is fairly simple.


----------



## brick

cheers Paulh, yeah i got all the simple recessive, double recessive and co-dominant/dominant genetics etc etc etc down pat, but some of the more in depth terminology to do with what causes different colours etc etc a bit confusing. thanks for the links, i will give it a good read over

dave


----------

