Could someone explain this to me?

[Family Jewels]

Special, Mystic, and Mojave are good examples of allelic heterogeneity, meaning that (as far as anyone can tell) they all occur at the same locus. When an animal has two of these mutations, they are considered compound heterozygous. http://www.newenglandreptile.com/ind...cts-like-super

Lesser, mojave, butter, special, mystic, phantom (and probably a few others that I'm forgetting) all occur at the same location, and an individual animal can only have a maximum of two alleles per locus. This is why if you breed a BEL (lesserXmojave) to a normal, you cannot produce more BELs. The BEL can pass on lesser *or* mojave, but not both. Meanwhile, you could breed a Pastel Yellow Belly to a normal and produce more Pastel Yellow Bellies, because those genes are independent.

Only a maximum of two alleles can occur at a single locus, as each side is inherited from each parent. Think of homologous chromosomes like the right and left side of a ladder, and morphs are hanging out at each corner where a rung meets the side of the ladder. You could have two albinos hanging out on the 10th rung, a normal and a lesser sitting on the 1st rung, plus two pastels on the 2nd rung. That ladder would represent an albino super pastel lesser, right? That's because all those morphs occur at different loci (or "rungs") and the morphs on one rung don't have any effect on any of the other rungs. They don't care about each other. However, special, mystic, and mojave, etc. will only hang out on the 4th rung. They can't occur anywhere else, and each side of the ladder can only come from one parent. Hence, you can only have these possible outcomes:

"Mojave-Normal" bred to "Special-Mystic":

Mojave-Special (aka "Crystal")
Mojave-Mystic (aka "Mystic Potion")
Normal-Special (Special)
Normal-Mystic (Mystic)


I should point out that allelic heterogeneity (or compound heterozygosity) used to be relatively rare in ball pythons, but it is becoming more common as we discover more allelic traits... for example, a Highway ball is a Gravel-Yellow Belly and can therefore only pass on one of these two genes to offspring. Just like a Mystic Crystal (special-mystic), it is heterozygous for each trait, but it has no normal allele at that given locus, so it is incapable of producing normals.
http://www.newenglandreptile.com/ind...uper-balls/als