Here's a very basic genetics lesson for heterozygous traits, such as pied, albino.
Every animal has two copies of a gene. That gene can either be expressed or not expressed. In some cases, one copy of a particular gene may be "stronger" than another, and that "stronger" gene gets expressed. With heterozygous traits, the "stronger" gene is the gene that causes normal coloration, whereas the "weaker" gene is the gene that has the morph that you want, but when it's paired with a normal coloration gene it can't compete and so doesn't get expressed in the animal's coloration.
So, say that the "strong" normal coloration gene is represented by "P" (you'll see why I'm using this notation in a second), and let's say that the pied gene is represented by "p." So, a normal animal with no pied genes would be PP, a heterozygous animal (an animal that has 1 gene for pied and 1 for normal) would be Pp, and a pied animal would be pp.
The following is called a Punnett square, named after a geneticist who developed this table to help estimate the probabilities of genetic outcomes. It's very helpful for figuring this out. You put the father along the top (I have his genes in blue), and the mother along the side (in pink), and the potential babies are are in the inside of the table (in orange).
As you can see here, each baby has a 25% chance of getting both normal genes (PP, or homozygous for normal), a 50% chance of getting one normal gene and one pied gene (Pp, these animals are known as being heterozygous for pied), and a 25% chance of getting both pied genes (pp, or homozgyous for pied). Since pied is a recessive "weak" trait, an animal needs to have both of the pied genes (aka be homozygous) to be pied.
One thing to note is that it's impossible with most heterozygous traits to tell heterozygous animals from normal animals, since the normal coloration gene wins over the pied gene, and all of them look normal. I say most, because some het pieds do have markers, although whether or not those markers are trustworthy is still up for debate. In a heterozygous to heterozygous breeding like the example above, 75% of the animals will likely appear normal (3 out of 4), but of those animals that appear normal, 2 out of 3 (66%) may actually be carrying a pied gene. This is where you get funky percentages such as 66% het for pied in some ads. It's a completely legitimate and proper way to advertise these animals. You're taking a risk purchasing these animals because there's still a 33% chance that the animals actually are completely normal.
To improve your odds of getting a recessive trait to become expressed, you can breed a heterozygous animal (a het) to a homozygous animal (like a visual pied). Here's the outcome of that breeding:
As you can see, you will get 50% normals, and 50% pieds. Not only that, but every normal animal you get has a 100% chance of having a pied gene, so these are known as 100% heterozygous animals.
I hope this helps you out! Keep in mind that this applies to every heterozygous trait, and it even applies to codominants. For example,yellowbellies and mojaves are actually heterozygous for a pure white snake (ivory), but instead of the gene being "weaker" than the normal gene, it's actually "stronger", so it gets expressed. But, it's actually even stronger than you think, because a double dose (a homozygous animal) of the gene results in an even more dramatic expression of that gene.
thank you for the help.
