What is "t-" and "t+" mean...

Dear VPI,

I've heard about and seen pictures of a lot of snakes, mostly albino retics, and some are marked t+ and some aren't.

What exactly does it mean when it said they are “t+”?Thanks, kevin  

 Dear kevin,

"t+" means "tyrosinase-positive" and "t-" means "tyrosinase-negative." 

Tyrosinase is an enzyme that acts on tyrosine, an amino acid that is the basic building block of melanin and a suite of other dark pigments that are called melanin-related pigments.

A tyrosinase-negative albino is an albino that does not have functioning tyrosinase or has a defective tyrosinase that does not work correctly, and so no black melanin can be produced. Also no melanin-related pigments are produces.  A tyrosinase-positive albino has functional tyrosinase and it is able to complete the first and second steps of the multi-step process of black melanin synthesis. Some other enzyme along the synthesis is missing. Tyrosinase-positive albinos do not make black melanin, but they do make other melanin-related pigments. Melanin-related pigments are mostly dark colors and they include a purple-gray, dark gray, gray brown, a dark yellowish brown, and several shades of brownish-red, dark red or medium red.

 Examples of t- albinos would be albino ball pythons and albino Burmese. T+ albinos would include Bob Clark's albino retic, caramel-albino ball pythons, and VPI's lineage of red-albino blood pythons.   DGB