Genetics questions you were afraid to ask...

[paulh]

Amelanistic corn snakes are T-negative. H. B. "Bern" Bechtel tested them some years ago.

T stands for tyrosinase. Tyrosinase catalyses the first two steps in the synthesis of melanin, the black pigment. Tyrosinase negative albino (T-neg or T-) means that the snake lacks black pigment because it cannot make tyrosinase. Tyrosinase positive albino (T-pos or T+) means that the snake lacks black pigment for some reason not connected with tyrosinase.

There are T-neg and T-pos albino black rat snakes (also tested by Bechtel). They look alike to me -- pink eyes and slightly yellowish in color. Crossing a T-neg black rat and an amelanistic corn snake produces babies that lack black pigment. Crossing a T-pos black rat and an amelanistic corn snake produces babies that have normal black pigment.

Some people use T-positive albino loosely to mean any snake with less than the normal amount of black pigment. That would make corn snakes like ultra, lava, hypo, and others all T-positive albinos. But our best guess now is that ultra has less than normal black pigment because of an inefficient tyrosinase enzyme, while the others have less than normal black pigment for unrelated biochemical reasons. So in that sense, "T-positive albino" is an unnatural grouping.

Clear as mud?

[Ssthisto]

Cheers for that, Paul - didn't know that Amel corns had been tested as T- but that's good to know.

That said, have the tests been done to determine whether the many flavours of hypomelanistic-effect genes in Corns actually *are* tyrosinase positive? Theoretically speaking, would it be possible for something like an Ultramel to be T- even though they have dark pupils / sometimes greyish pigmentation?

[paulh]

In mice, the albino mutant is T-, and there are half a dozen mutant alleles of albino that produce varying amounts of melanin. The interpretation is that those other alleles produce different abnormal versions of tyrosinase. Each tyrosinase version can produce different amounts of melanin, but none is as effective as normal tyrosinase. And if two different mutants are in the gene pair, each one produces its own version of tyrosinase and the phenotype splits the difference.

My interpretation of ultramel is that the ultra mutant produces an abnormal tyrosinase that can produce some melanin. The amelanistic mutant produces a nonfunctional version of tyrosinase that cannot produce melanin. And ultramel splits the difference between an ultra corn snake and an amelanistic corn snake.

We can't call the ultra mutant T-negative because it can make melanin. There doesn't seem to be any term for a T-positive state that is missing on three cylinders.

[negri21]

leopard gecko .

blazing blizzard (snake eyes) x diablo blanco (red eye) = ?

cheers

[Ssthisto]

Blazing Blizzard is Blizzard + Albino - the snake eyes thing MIGHT be genetic, but I don't know the exact heritability, nor do I think anyone else does.

Diablo Blanco is Blizzard + Albino + Eclipse.

So you'd get Blazing Blizzards het Eclipse.

[negri21]

Originally Posted by Ssthisto

Blazing Blizzard is Blizzard + Albino - the snake eyes thing MIGHT be genetic, but I don't know the exact heritability, nor do I think anyone else does.

Diablo Blanco is Blizzard + Albino + Eclipse.

So you'd get Blazing Blizzards het Eclipse.

cheers,

would they have normal eyes ?

[Ssthisto]

I'll phrase it this way:

You can't guarantee they'll have *abnormal* eyes - because they'll only be het for Eclipse - but if some or all of the babies pick up the Blizzard-Snake-Eye trait (however it is that it's inherited) then you might get some non-normal eyes.

[negri21]

cheers for that .

[brian_210]

I wonder if anyone can help me, I have the genetics for herpers book and I'm trying to understand it all..but I do better learning in practice.

I want to know if I have a fat tailed gecko with a co-dominent (visual male) gene, and breed it to a normal fat tail female, what would the outcome be? as in..what % if any would have the visual trait, would all of them carry the gene? I really need help with this so any info would be great

[Ssthisto]

If your male is heterozygous for the codominant gene (he has one copy, not two) then breeding him to a normal female would produce (on average, over thousands of offspring) half non-carriers that are completely normal in appearance and genetics and half exactly like him (heterozygous carriers that show the visual trait).

If your male is homozygous for a codominant gene (he has two copies of it) then bred to a normal female he will produce ALL heterozygous-codominant offspring.

For a fictional example, imagine that "yellow AKA Super Tan" is the homozygous form of the codominant "tan" gene, and that a heterozygous-Tan is visually tan with lighter stripes in colour; a homozygous-Tan is yellow and white.

Breed a "Tan" to a normal, and you'd expect half normals and half Tans. The normals don't carry Tan - or they'd BE Tan.
Breed a "Yellow" to a normal and all the babies would come out as Tan.