An animal inherits one copy of each gene from each of its parents.
A recessive trait will not be visible unless the animal has 2 copies of a gene (one from each parent).
A dominant trait will be visible if the animal has only 1 copy of the gene.
A co-dominant trait will be visible if the animal has only 1 copy of the gene, and will produce an animal that looks DIFFERENT from the animal with 1 copy, if 2 copies of the gene are present.
Heterozygous means that there is one copy of the gene present. Thus, a 'het for albino' carries 1 copy of the albino gene. Since albino is recessive, a 'het for albino' will look like a normal ball python. A pastel also carries one copy of the pastel gene. Since pastel is co-dominant, it will look like a pastel. Pinstripe is dominant. A pinstripe that carries one copy of the pinstripe gene will look like a pinstripe.
Homozygous means that there are two copies of the gene present. An albino carries two copies of the albino gene, and since albino is recessive, looks like an albino. A super pastel carries two copies of the pastel gene. Since pastel is co-dominant, it looks like a super pastel. A super pinstripe carries two copies of the pinstripe gene, but since pinstripe is dominant, it looks like a pinstripe.
Co-dominant traits are among the most common mutant color/pattern genes found in ball pythons. Recessive traits are less common, and dominant traits are (so far) pretty rare.
Spider is not a dominant gene, by the way. If it were dominant, homozygous animals that look like spiders would exist, but none have ever been produced. It is possible that spider is co-dominant with a lethal super form, or that something else is going on.
If you're still with me....
Now you know that there can be no such thing as a het for pastel, because all pastels ARE hets. If the animal from a pastel breeding looks normal, it IS normal.
You know that only traits that cause animals to look exactly the same, whether they carry one or two copies of a mutant gene, are dominant.
You know that animals that carry one copy of a recessive gene will look normal, so they should only be purchased from a trusted person (and having verifying paperwork is a good idea).
One final tip: When you see a '50% het for albino', what that actually means is that someone bred a het for albino to an animal that did not carry the albino gene. An animal that has one copy of a gene can pass on either the mutant gene, or the normal copy of the same gene that it also carries. As a result, about 50% of its offspring will have the mutant gene, and the other 50% will have the normal gene.
Since recessive traits that are heterozygous produce an animal that looks normal, you cannot tell which babies inherited the gene, and which did not. So a "50% het for albino" doesn't have half the gene, it has a 50% chance of carrying the gene, and a 50% chance of not carrying (being completely normal). 50% refers to the odds that the animal has the mutant gene. Once it is bred to another het or to an albino, it will become clear whether the gene is present--it will either produce albinos, which verifies it carries the gene, or it will not produce any albinos, which means it probably doesn't carry the gene.
Once the gene is proven to exist, it becomes '100% het for albino', or a 'proven het for albino'.
If all of that is FAR too confusing, don't worry. Start small, with a morph that you like, and learn how that morph's genetics work. You can learn the rest as you go.
Originally Posted by WingedWolfPsion
An animal inherits one copy of each gene from each of its parents.
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