The link gives a good overview of some of the biology.



Mice have at least 50 genes that affect color and/or pattern. These are scattered over most of the mouse's chromosomes. And many of those genes have more than one mutant allele. Snakes probably have considerably more than 50 genes that work as a team to make normal coloration. One mutant gene disrupts the work of the team, and the snake no longer looks normal.



>I thought that Lucy’s had to be homozygous for the leucistic gene, in order to be white?, And basically, if a lucy is bred to a normal, the offspring are all hets for leucism?



It depends on the mutant gene. In the Texas rat snake, the leucistic mutant gene is recessive to the normal gene. When a leucistic Texas rat is mated to a normal, all the babies have a leucistic mutant gene paired with a normal gene and look normal. A dominant white cat has white fur and blue, green, or orange eyes. Such a cat may have either a pair of dominant white mutant genes (homozygous) or a dominant white mutant gene paired with a normal gene (heterozygous). Mating a heterozygous dominant white cat with a normal is expected to produce 50% dominant white cats (heterozygous) and 50% normal. And then we've gone over the leucistic ball pythons that are heterozygous because they are lesser platinum//mojave.



>Why is it incorrect to call a Mojave a het for leusism?



Technically, a ball python would be het leucistic if it had a mutant gene named leucistic paired with a normal gene. A mojave is certainly heterozygous. But as far as I know, there is no mutant gene named leucistic in ball pythons.



Even if we are pretty relaxed about the naming, het leucistic is a confusing term. It could refer to a mojave, a lesser platinum, a lesser platinum//mojave, or several other genotypes. Unique names are best.



Paul Hollander


genes and chromosomes

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