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I've been wondering for some time now, how is it possible for a snake to be 100% het for a morph?

When a Morph is breed to a normal the babies are 100% het

>>I've been wondering for some time now, how is it possible for a snake to be 100% het for a morph?

In reality, it isn't really possible for a snake to be anything less than 100% het. All hets are 100% heterozygous at that particular locus.

A snake is heterozygous for a recessive trait if it carries the a recessive allele (e.g. albino) that is masked by a dominant allele (e.g. normal pigment). In this example, the snake would look normal, but carry the albino allele. You couldn't tell this snake from any other normal snake. Therefore, a snake either is heterozygous or isn't.

The percentages you see in snake breeding are actually the probability that the snake is a het. These probabilities are based on the possible outcomes from a mating.

For example, if I mate two hets (for albino) together, 25% of the offspring should be normal (non-hets), 25% of the offspring should be albino, and 50% should be heterozygotes. However, there is no way to tell the hets from the normal offspring, so you just have to guess based on the probability of any single "normal looking" snake being het.

So you get a few albinos and a bunch of normal looking snakes. In the example above, 1/3 of the normal snakes will be normal and 2/3 will be hets, so therefore, if you choose one at random, you have a 66% chance of it being heterozygous.

Partly for convenience and sometimes out of ignorance, snake breeders call them 66% hets. They aren't really 66% heterozygous at all, in reality, they have a 66% chance of being heterozygotes. And if they are hets, then they are completely heterozygous. If they are not, they are just normal snakes.
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Chris Harrison

>A snake is heterozygous for a recessive trait if it carries the a recessive allele (e.g. albino) that is masked by a dominant allele (e.g. normal pigment).

Right. Recessive mutant genes are the most common, but there are also dominant and codominant mutant genes, which can also be heterozygous.

A snake is heterozygous for a dominant mutant gene if the mutant gene is paired with a normal gene, but the presence of the normal gene is masked by the dominant mutant gene. This is the mirror image of the situation with a recessive mutant gene. In both cases you can look at the snake and tell the identity of only one gene out of the pair. The other gene can only be determined by breeding tests or pedigree.

Unfortunately, there haven't been many dominant mutant genes turned up in snakes, yet.

And to complete the picture, a snake is heterozygous for a codominant mutant gene if the codominant mutant gene is paired with a normal gene. In this case, the heterozygous snake doesn't look normal and doesn't look like a snake with a pair of identical mutant genes, either. IOW, you can look at a snake and tell the identity of both genes in the pair. Tiger in the reticulated python is a good example of a codominant mutant gene.

Paul Hollander