I am by no means an expert, but I will do my best to explain it to the best of my knowledge....



T-positive refers to a recessive gene called tyrosinase which is thought to be present in the boas referred to as T-positive. To my understanding, the tyrosinase gene assists in production of melanine, however does not allow for full melanine production. Melanin is the gene that causes dark/black pigment in boas.



Therefore, since melanin is being produced, but not completely due to the presence of tyrosinase, a t-positive boa is actually a form of an incomplete albino. I use the word incomplete because it is not a full albino due to the presence of melanin, but the reduction in melanin leaves room for argument that a t-positive is an incomplete albino.



The t-positive gene is not compatible with the common kahl or sharp strain albino, as it is a recessive mutation of it's own which was started by VPI. That's why it is referred to as VPI t-positive. I believe the story begins with a normal pairing of boas producing a few "freak" boas, which were raised up and proved out to be genetic in the offspring, and are now known as t-positive.



I do not know if anyone has ever actually done a test to prove the presence of tyrosinase, I believe it is still a theory. However, it has been proven to be a genetic recessive that may be one of the most beautiful boas in existence.



T-positive boas are easily recognizeable, even at birth. They stand out from normal appearing offspring much like an albino would next to normals when born. They are not as extreme as normal albinos, but they seem to glow.



They have what I call the "duh factor." You can look at a litter of t-positives and normals and go DUH that is a normal, and DUH that is a t-positive. They are very different from one another, from birth all the way into adult hood.



There are several strands of animals thought to be T-positive, including colombian VPI t-positive, nic t-positive, argentine t-positive, and CA T-positive, none of which are compatible with one another (that I know of). There is also developing projects which may prove that sharp strain albino and BWC may be a form of t-positive, because when they are bred together form a visual double het which looks very much like a t-positive.



I have several colombian t-positive animals in my collection, and they are my favorite by far. I have attached pictures of them. The difference between these and a normal should be very obvious.



I hope this helps



One of my own VPI boas, a VPI Motley, as a baby and as an adult, the difference between this and a normal motley should be obvious











Another one of my own, a female VPI t-positive, as a baby and as an adult











Even as adults, T-positives are some of the most stunning animals I have seen. it's my favorite gene to work with.



Just for the sake of comparison, here are a few argentine t-positive specimens owned by Tim at Special K. I took this picture at Tinley Park last month. Like i said, these have the "DUH factor." It's obvious which is the normal, and which is the t-positive







Tony

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