Another possibility is that there is another gene that is epistatic to the one that codes for the deposition of melanin in the scales. Epistasis is when a gene at one locus alters the phenotypic expression (outward appearance) of a gene at a second locus.



A simplified example is coat color in Labrador Retrievers. Black coat color is dominant, but there is a second gene, that is epistatic to the first, that determines whether or not pigment will be deposited in the hair. That gene is simply farther "upstream" in the cellular pathway. The epistatic gene takes precedence no matter what is going on later in the pathway. If the epistaic gene is homozygous dominant or heterozygous, then color gets deposited in the hair. If it is homozygous recessive, then color does not get deposited, no matter if the animal is homozygous dominant for black hair or not. The result of being homozygous recessive for color deposition in the hair is the yellow lab.



This may be what we're seeing in melanistic thayeri. There may be an epistaic gene responsible for the deposition of melanin in the scales. If it is present in the homozygous dominant or heterozygous state, then if the animal is homozygous for melanistic the melanin gets deposited and the result is the phenotypic all black snake. If the epistatic gene is homozygous recessive against melanin deposition, then the snake may phenotypically appear muddy or normal.



This could explain the appearance early on of the trait seeming to be simple recessive. many animals my have had the "upstream" epistatic gene to express melanin deposition in the scales. Selective breeding could have messed with the upstream gene in unforseen ways leading to the model #2 that we see today...melanin deposition in the scales appearing to occur somewhat "randomly". Just a thought.
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Species kept:



Nuevo Leon Kings

Kunasir Island Rats

San Luis Potosi Kings

Axanthic Desert Kings

White Oak Gray Rats

Corns



Coming Soon:



Western Green Rats

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