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Paul Hollander
at Sun Dec 7 17:22:22 2003 [ Email Message ] [ Show All Posts by 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? :D
Paul Hollander
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Compatibility means (more) - Paul Hollander, Sun Dec 7 17:22:22 2003