Genes come in pairs. A ball python has over 20000 pairs of genes. So the first thing to do is to figure out what gene pairs produce the snake's appearance.
White diamond mated to albino is a two gene pair problem.
White diamond snake's genes:
gene pair 1 = two Russo genes (R//R)
gene pair 2 = two normal genes (+//+)
Albino snake's genes:
gene pair 1 = two normal genes (+//+)
gene pair 2 = two albino genes (a//a)
// stands for a pair of chromosomes. R//+ would means that there is a Russo gene in the DNA molecule in one chromosome and a normal gene (+) in the corresponding location in the DNA molecule in the other chromosome.
To the best of our knowledge and belief, all the gene pairs except those two are made up of two normal genes. We can ignore all those other pairs. This includes the gene pair that holds two copies of the normal gene that corresponds to the pied mutant gene.
Each baby gets a gene from each of the father's gene pairs. And each of the babies gets a gene from each of the mother's gene pairs.
The white diamond gives a Russo gene from the first gene pair and a normal gene from the second gene pair. There are two copies of the Russo gene in the first gene pair. It doesn't matter which gene is given. And there are two copies of the normal gene in the second gene pair. It doesn't matter which copy is given there, either.
The albino gives a normal gene from the first gene pair and an albino gene from the second gene pair.
When you set up your Punnett square, put a R + on the top and a + a on the side. This is a one box Punnett square--all babies are R//+ +//a. In other words, every baby has a Russo gene and a normal gene in gene pair 1 and an albino gene and a normal gene in gene pair 2.
Assigning appearances to the genes is the hardest part. These snakes are Russo het albino. A Russo is lighter than a normal ball python but not white like the white diamond. So there is one appearance for each of the three possible gene pairs. The three gene pairs are 2 normal genes (+//+ --> normal appearance), a Russo and a normal gene (R//+ --> Russo appearance), and 2 Russo genes (R//R --> white diamond). When each of the three possible gene pairs produces a different appearance, the mutant gene is codominant to the normal gene.
There are three possible gene pairs for the albino gene pair (pair 2). 2 normal genes (+//+ --> normal appearance), an albino and a normal gene (+//a = het albino --> normal appearance), and 2 albino genes (a//a --> albino). Two appearances from three gene pairs with the het albino looking normal means the albino gene is recessive to the normal gene.
FYI, assigning appearances to a dominant mutant gene is the mirror image of the recessive mutant gene. There are 3 possible gene pairs--2 copies of the mutant (D for dominant) gene (D//D --> mutant appearance), a dominant gene and a normal gene (D//+ --> appearance is same as for D//D snake), and 2 normal genes (+//+ --> normal appearance).
Take a snake with a mutant gene paired with a normal gene. The snake's appearance determines whether the mutant gene is classified as dominant, codominant or recessive to the normal gene. The mutant gene is dominant to the normal gene if the above snake looks like a snake with two copies of the mutant gene. The mutant gene is recessive to the normal gene if the above snake looks like a snake with two copies of the normal gene. The mutant gene is codominant to the normal gene if the snake does not look like a snake with two copies of the mutant gene and does not look like a snake with two copies of the normal gene.
By the way, here is a link to a genetics guide I whipped up a while back: http://www.redtailboas.com/f115/no-f...s-guide-53782/
Hope that helps.
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