Quote Originally Posted by paulh View Post
Standard genetics definitions:
Homozygous = the two genes in a gene pair are the same.
Heterozygous = the two genes in a gene pair are NOT the same.

A het red axanthic ball python has a red axanthic mutant gene paired with a normal gene. Those two genes are not the same. Therefore, the gene pair is heterozygous. By extension, a snake with a heterozygous gene pair is also heterozygous.

A heterozygous snake may or may not look normal. It depends on the genes. In this case a het red axanthic ball python does not look normal. The belief that all hets look normal is a holdover from the days when all mutant genes were recessive to their respective normal genes. Those days are long over, but herper genetics terminology has mostly not caught up. It has with the red axanthic mutant.
The thing is... It's a codom mutation and the term "heterozygous" is usually used for recessives. Since axanthic is recessive and the gene was named red axanthic, he probably called them HRA's to avoid confusion. It just created more confusion though. It's a codom morph, not recessive, he probably shouldn't have used the term "het".