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Old 06-18-2009, 07:28 PM   #30
Susan
Quote:
Originally Posted by sweet~nichole~marie View Post
I have a question about interactions between the different genes . . .

In simple mendelian genetics you expect the dominant to overshadow the recessive traits, but when you start mixing multiple genes together that flies out the window.

an amel het anery snake (aaBb) shows the red but not the black, but looking at the genotype you would expect the gene that has a dominant allele in it to show through.

It is as if the recessive trait is "stronger" than the homozygous or heterozygous trait of another.

So, my question is (finally ) when trying to determine what your snake will look like, if you have any recessives in the mix, is that what will show?

Ex. aa Hh DD Ww BB Rr since the aa is the only trait that has 2 recessive alleles, it will be the one that shows, not matter how many other dominant alleles there are for other genes?

Thanks (in advance) for the clarification . . .I understand mendelian genetics, co-dominance, incomplete dominance, multiple alleles, polygenic traits, etc. but this doesn't seem to follow any of those patterns . . . Is there a name for the way the genetics of cornsnakes behave?
Corn snakes perfectly follow Mendelian genetics. The dominant genes are what we call the "wild-type" phenotype...the normal/classic corn snake. Each of the recessive genes affects the phenotype "away from" the dominant wild-type phenotype. So far, all but one currently recognized corn snake gene are recessive to wild-type. Only the tessera gene seems to be dominant to wild-type when in het form. We should know by this year's breeding results if there is a "super" form of tessera when it is in homozygous in an individual.

For example, the amel gene removes the black that is normally seen in the wild-type. The anery gene removes the red that is normally seen in the wild-type. A snake that is homozygous for amel has 2 recessive genes and no dominant wild-type gene to produce the black. If that snake is also het anery, then it has one recessive gene to remove the red, but one dominant wild-type gene to produce the red, so that amel het anery corn snake will still have the red but no black.

Now that same amel het anery corn snake still have both dominant wild-type genes at the lavender, caramel, motley, hypo, etc loci, so you do not see any of those recessive traits in the phenotype, just the amel as that is the only gene that has been changed from the wild-type normal-looking corn snake.

If your amel snake is now also homozygous for anery instead of just being het, the dominant wild-type genes to produce black and red have been replaced vy the recessive mutant genes so the snake will not have black or red and will be a snow corn snake. Add yet another pair of recessive genes to replace the dominant wild-type ones, for say, the pattern, and suddenly you have a snow motley corn snake!

Now some recessive genes can mask the effect of other recessive genes. For example, if a snake is homozygous for both caramel and anery, the phenotype will be anery as the effect of the caramel gene cannot be seen (for the most part; in some individuals with this particular genetic make-up, the yellow may be increased, but that really hasn't been proven 100%). The effects of hypo in an amel snake is also masked, but some of the other melanin-decreasing genes, like lava, some people say you can see a difference.

If you are still confused, I'll try again.