Horse Color Genetics: Re-Explaining Heredity and Basics

To go back to the basics, as I've learned more about genetics I have thought of better ways to explain how it all works. My first post about heredity was fine, but I thought I would re-write it with a different example.

Let's start with a genome sequence: Ee, AA, Cc, LPlp

If you've tried to understand genetics, then you may have seen something like this. This is a way to abbreviate the horse's color, but being able to read it is what takes practice.

For each individual gene, there are two alelles together that make up the gene. Each alelle individually has the chance to be either 'turned on' or 'turned off'. The 'on' genes are capitolized. The 'on' genes are called dominant, and 'off' genes are recessive. If I ever refer to dominant and recessive, always think of a light switch. If they are reccesive, the light switch is turned off.

When any creatures breed, each parent must give only one alelle from each gene to it's offspring. That means when they breed, the gene will split, and the depending on the parent, they will get either two on genes, one of each, or two off genes.

Using the example above, the gene AA was both turned on. When both genes are turned on, or both turned off, this is called homozygous. 'Homo' means the same; both allelles are the same, and you know what the baby will inherit.

The rest of the genes, Ee, Cc, LPlp, are one of each. That is called heterozygous, 'hetero' meaning different. If this horse were to breed, we can only make a not very good guess as to what color the baby will be, because it is 50/50 whether they get the 'on' gene or the 'off' gene.

If you are still confused, let's use flowers for a simple example. If you breed a red flower and blue flower together, the baby will be purple. One red gene from the red flower and one blue gene from the blue flower. However, the genes inside the baby will still be red and blue. If that baby were to breed with a red flower, then those genes would split. THAT baby would get one red gene from the red parent, and either a red gene OR a blue gene from the purple flower. So that baby would either be red or purple.

So if I were to say that the horse in the example is heterozygous E, that means that there is one dominant gene and one recessive gene. If I said that the horse was homozygous dominant A, that means that both A genes are turned on. It is important to know that when I refer to homozygous, I usually mean homozygous dominant, meaning both genes turned on, versus homozygous recessive, both genes turned off. When a breeder advertizes their stallion for a certain homozygous gene, they are referring to homozygous dominant.

I'll use a different post to go back and re-teach you about the basic colors, and how all this applies.