Reptile & Amphibian Forums

...between dominant and co-dominant genes?

Thanks!
Judy
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1.0 red cape gopher (Caesar)

A dominant gene displays its whole effect with only one copy present. A codominant gene shares being dominant so it has a small effect if one copy is present and a large effect if two copies are present. When you only have one copy of a codom gene, it's sharing its dominance with the wild type gene. In snake color morphs the presence of two copies of a codominant gene is usually called super- super tiger, super jungle, ect.
An example of codominance in humans-
Red blood cells have three genes for a particular 'pattern' of sugars on their surface- pattern A, pattern B, and no pattern, or O. Since these are codominant, your blood type can be AB (both patterns present), AO (called A), BO (called B), or OO (called O). If you think about it these explains why O is the universal donor and AB is the universal recipient.
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Peter: It's OK, I'll handle it. I read a book about something like this.
Brian: Are you sure it was a book? Are you sure it wasn't NOTHING?

Ahhhhh....thank you very much!

Mostly true, except that the term "codominant" is often confused with incomplete dominance. A lot of the genetic morphs in snakes appear to actually be incomplete, rather than codominant. Codominant means that the phenotypes of both genes are expressed individually. This is true in blood type, AB means that your blood cells will have both A and B antigens expressed, not a single blended AB antigen. In some coat colors of some animals, this can also be the case. Carrying both a red and white gene which are codom to each other will produce a mix of red and white hairs, not a single light red color. On the other hand, incomplete dominance produces a blending of the two phenotypes; this appears to be the case with many of the morphs.