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Howcome incompatible albinos produce normal colored offspring? How does an albino have any other color gene to pass along? I can't seem to get my brain around this one.

Also, same type question for axanthic and albino crosses. Where does the normal gene come from?

Thanks, Amy C.

>Howcome incompatible albinos produce normal colored offspring? How does an albino have any other color gene to pass along? I can't seem to get my brain around this one.
>
>Also, same type question for axanthic and albino crosses. Where does the normal gene come from?

According to the human genome project, humans have approximately 35,000 genes in the cell nucleus plus stretches of DNA for which there is no known function. Humans have 23 pairs of chromosomes, and that means a lot of genes per chromosome, not just one gene per chromosome. We have no good estimate of the number of genes in a snake genome. My guess is somewhere in the tens of thousands of genes.

To simplify thinking about genetics problems, we usually ignore all the normal genes. So that albino snake has a pair of albino genes somewhere on one pair of chromosomes (one albino gene on one chromosome, and the second albino gene on the other chromosome). And that albino snake also has tens of thousands of normal genes elsewhere on the same pair of chromosomes and other pairs of chromosomes. One pair of those other genes are normal versions of the axanthic mutant gene.

An axanthic snake has a pair of axanthic genes somewhere on one pair of chromosomes. And that axanthic snake also has tens of thousands of normal genes elsewhere on the same pair of chromosomes and other pairs of chromosomes. One pair of those other genes are normal versions of the albino mutant gene.

If we mate an albino to a normal snake, then all the babies are normal. We get this result because the normal snake provides the normal version of the albino gene. And if we mate an axanthic to a normal snake, then all the babies are normal because the normal snake provides the normal version of the axanthic gene.

Mating an albino to an axanthic produces normal-looking babies because there are two sets of genes to think about, not one set as in the albino x normal mating. In the albino x axanthic mating, the axanthic provides the normal version of the albino gene, and the albino provides the normal version of the axanthic gene.

Let's do a graphic with two pairs of chromosomes and ignore all the other chromosomes. The letter a = albino, A = the normal version of the albino gene, x = axanthic, and X = the normal version of the axanthic gene.

Albino snake, with a pair of albino (a) genes and a pair of the normal version of the axanthic gene (X):
----------a--- --X----
----------a--- --X----

Axanthic snake, with a pair of axanthic (x) genes and a pair of normal versions of the albino gene (A):
----------A--- --x----
----------A--- --x----

Mating these two snakes together gives normal-looking babies because they have the following pairs of chromosomes:
----------a--- --X----
----------A--- --x----

And we are still ignoring all those tens of thousands of other pairs of genes (all assumed to be normal genes) possessed by both snakes. A mutation of one of those other genes might produce pastel. A mutation of another of those other genes might produce pied. And on and on.

Clear as mud?

Paul Hollander

Thanks for the explanation. It is greatly appreciated. I was thinking that if an albino can only give the albino gene that in mataing two incompatible albinos, one would have to become dominant. I'll try to 'wrap my brain around this one' again.

Sorry to be late getting back to you. I was on annual leave last week (my home computer is down) and then we went to Daytona.

Herpers are absolutely NUTS! Riding thru a hurricane to buy and sell reptiles! Yee hah!

Amy C.

I will try to make this simple and still explain things.
first, regarding two incompatible albinos crossing.

A phenotype, the visible trait, is albino however they have differant genotypes, the part of their genetic make up that has a mutation which makes them albino.

Also, each animal has two sets of genes, one from each parent. In order to get an Albino you need the parents to carry the albino genotype wether it is expressed in the phenotype or not (homoxygous and heterozygous), and the albino genotype they carry must be the same. The albino is the offspring that recieved that gene type from both parents, if it recieved one from one parent and a normal gene from the other it would appear normal, that is dominant over albino, and heterozygous for albino, carrying the gene but not expressing it.

when you cross two ressesive traits incompatible with each other the offspring look normal but are hets for both kinds, why do they look normal?
They look normal because they recieve one genotype from each parent, and nothing affects the phenotype, the reason they are normal is because the parents, althought they had a pair of genes the same still carried the normal gene, it was just masked.

If you have trouble understanding this, look up punnet squares and do some research on ressesive genetics.