Can this be done ?????

[paulh]

I don't believe it can be done, because they both are on the same locus/allele (can't remember which is the right term)

The way I understood it was there are two spots

nn - normal
yn - yellow belly
yy - ivory
sn - specter
ss - super specter
sy - superstripe

Because these two genes are allelic they are on the same locus. (Think of a ladder, each rung being a locus) so you can only have a gene on each end of that rung. Where as a morph on a different locus would be a different rung, if that makes sense....

DISCLAIMER: I am not 100% on this description, as I'm still learning the genetics as well. Please feel free to tell me my mistakes! This is just how I understand it currently.

I've seen a number of web sites that say there is a gene on each end of a "rung". That is wrong.

Two genes are alleles because they are at the same locus (location in the DNA in the chromosomes). It takes hundreds or thousands of "rungs" in a DNA ladder to make a gene, and each DNA "ladder" contains millions of "rungs". The sequence of "rungs" determines the gene's makeup. And this is a pretty simplistic description.

Chromosomes come in pairs -- 23 pairs in humans, 18 in boa constrictors, and (I think) 18 in ball pythons. There is one DNA "ladder" in each chromosome of a chromosome pair. The corresponding locations in the two chromosomes of a chromosome pair are the same locus. We say there is one locus with two alleles, but it must be understood that the two alleles are in separate chromosomes.

The genes for two different traits are in the DNA "ladders" in different chromosome pairs. Or they are different series of "rungs" in different locations in the same chromosome pair.

A sperm or egg gets one chromosome from each parental chromosome pair. When a sperm and egg fuse, the chromosome pairs are reestablished, which also reestablishes all the gene pairs.

A pair of chromosomes:
-----a----B---------- = the DNA ladder in one chromosome.
-----a----b---------- = the DNA ladder in the other chromosome. Each - stands for a gene. The a and b genes are different genes in different loci. The B and b genes are alleles.

By the way, if you see an X-shaped structure in a cell's picture, it is not a chromosome pair. It is a single chromosome that is dividing to become two rod-shaped chromosomes.

Hope this helps. A genetics text will have a more detailed explanation.