Reptile & Amphibian Forums

I was reading all the posts about crossing the pieds with albinos and other morphs and was just wondering what everyone thought about the possibility that some morphs aren't compatible. Do you think that it is possible that one morph is so strong in its appearance that it will totally overwhelm the other. Just something that popped into my head after reading all the morph posts earlier. Thanks, Todd

I know that there are several different strains of albino in leopard geckos.

With balls, I believe that if you breed any 2 albinos, you'll get albino offspring.

With leos, if you breed a Tremper line albino with a Las Vegas line albino, you'll get normals that are double het for both kinds of albino.

Theoretically, you can breed the double hets back to each other and get a leo which shows both kinds of albinism. Don't know if that's been done yet.

The point is that there must be some genetic variations which are incompatible with one another.
-----
3.6.3 Leopard Geckos (1.4.3 Albino)
~~25 Leo eggs cookin'~~
1.1 Ball Pythons
1.0 African Fat Tail Gecko
0.1 Okeetee Corn Snake
1.0 Blair's Phase Gray Banded Kingsnake

You are writing about the genetics concept of epistasis, where the presence of one (or more) mutant genes masks the presence of other, independant mutant genes.

I'm not as up as ball python mutants as I could wish. But I've personally seen epistasis in a number of species. IMHO, if epistasis hasn't shown up in ball pythons yet, it is just a matter of time until it does. For example, albino may mask pastel. I just don't know if anybody has tried to combine the two.

Paul Hollander

that two genes are identical or alleles. Alleles are different forms of the same gene and therefore have the same location in the genome. Independant mutant genes have different locations in the genome and would be called incompatible. A locus (plural = loci) is one such location in the genome.

In ball pythons, we most commonly see the effect of a single mutant gene. For example, albino, pied, ghost, pastel, and others are single mutant genes. All are independant mutant genes, AFAIK.

Most commonly, the list of alleles for a given locus contains two genes -- the normal or wild type gene and one mutant gene. Sometimes the list of alleles for a given locus contains multiple alleles -- the normal or wild type gene and two or more mutant genes. A dominant mutant gene is dominant to the wild type allele, a codominant mutant gene is codominant to the wild type allele, and a recessive mutant gene is recessive to the wild type allele. But we can also specify comparisons between two mutant alleles. Depending on how the breeding results come out, a mutant gene that is dominant, codominant, or recessive to the wild type allele can be dominant, codominant, or recessive to another mutant allele. Even more complicated, a mutant gene that is recessive to the wild type allele can be dominant to one mutant allele, codominant to a second mutant allele, and recessive to a third mutant allele. I haven't heard of any cases of multiple alleles in ball pythons, yet. There is a case in the black rat snake, though.

For example, in the ringneck dove, the d locus has three alleles -- the wild type allele, the blond allele, and the white allele. White and blond are recessives because they are recessive to the wild type allele. A dove with one wild type gene paired with either a blond allele or a white allele looks like a bird with a pair of wild type alleles. But blond is also dominant to white (and white is recessive to blond), because a dove with one blond mutant gene paired with one white mutant gene looks like a dove with a pair of blond mutant genes. The only white doves have a pair of white mutant alleles. So in blond and white we have two "compatible" mutant alleles, but the phenotype of only one shows when they are in a pair.

When we combine two independant mutant genes in one animal, we generally see the effect of both. But we may see the effect of only one, as in epistasis (see my earlier post). Or the two independent mutant genes may be mimics and produce the same phenotype. Those incompatible albinos in leopard geckos would be called mimics.

So that is about three different ways to have mutant genes but hide the effects. Clear as mud?

Paul Hollander

Thank you for the very in depth expanation. Even though I honastly wasn't looking towards such a scientific explaination it was incredibly informative and I enjoyed it tremondously. Todd

In addition to the possibility of one morph completely covering another (for example how would you see the stripe in a striped leucistic) there are a couple of other possibilities that we might run into eventually also.

One is that two morphs might turn out to be alleles - different mutations of the same gene. This might actually be a pleasant surprise. When someone goes to cross say albino and caramel if it turns out that they are different mutations of the same gene then neither parent will have a normal copy of that gene so the babies can't be normal. It's hard to know what they might look like though, maybe albino, maybe caramel, maybe half way in-between or something different. This is just an example and with the large number of genes we may not find any allele morphs any time soon but a possibility that one should consider, especially with mutations that seem to have some of the same characteristics.

Another possibility is that two mutations might be linked in that they are different mutations of different genes on the same chromosome. In this situation the babies from the initial homozygous X homozygous cross are normal looking double hets as expected however it becomes harder than the expected 1 in 16 to make the double homozygous in the next generation. This is because when each double het parent is making their copy of that chromosome for the offspring the only way for the the chromosome to get both mutations is if there is an odd number of crossovers between the two source chromosomes between the two mutant genes. Depending on how close together the genes are this might be very difficult. I've heard some information that sounds like this could possibly be happening in leopard geckos and it is documented with the long hair and banded mutations in Syrian hamsters. I've also suspected that green and labyrinth might be linked in Burmese pythons but it could also just be a case of epistasis where the green/patternless mutations just "stands over" or covers the labyrinth appearance.

One other possibility I can think of is that two genes might be a lethal combination. Maybe with the leopard geckos the combined effect of the two mutations results in an animal that it too sickly to live.

Many of the combinations so far have been stunning and I’m sure there will be many more but just keep in mind nothing is a sure thing. Most will likely come off without a hitch as expected but the above possibilities might make a few of them more interesting.