Reptile & Amphibian Forums

Ok, I was reading up on genetics, I know, probably a tired subject now. Anyway, one page I came across gave some examples of breeding expectations and it mentioned double homozygous. It gave the example of Snows saying if you bred double homozygous snow x double homozygous snow you would get all snows. Now, why does it have to be double homozygous? And what exactly is double homozygous? I know what homozygous is, but double? Isn't that just another way of saying that if you breed snow to snow you're getting snows? I think I confused myself.

Snows are homozygous for two independent recessive traits, albino and axanthic. Together these traits make a snow (no melanin and no yellow pigment = pretty snake). Your right though, breeding 2 snows together will give you all snows. (although there aren't many out there can can actually do this right now) Breeding a snow to an albino will give you all albinos het. snow (het axanthic), and breeding a snow to an axanthic will give you all axanthic het. snows (het albino). Hope that helps clear things up for you.
Evan Jamison

Double Homozygous simply means to show two individual traits, whether they are recessive or dominant, in the same animal. A sunglow is double homozygous showing both albinism AND hypomelanism. A striped albino is also double homo showing both the striped and albino traits.

np

Remember that genes come in pairs, one from each parent (some gender related genes are the exception). Homozygous means the two copies match. A snow (double homozygous for both albino and the separate gene axanthic) has no room left for a normal copy of either the albino or axanthic genes. Because it's homozygous for both mutations you know it can only pass the mutant copy of each gene on to its descendents. Now if you had a pair of double heterozygous for snow snakes there would be normal copies of each gene in the mix.