In this lesson, we’ll be talking about the basics of how genes work, how to read them and what the difference is between dominant and recessive. Once you understand this part the rest will be MUCH easier!
Let’s start with genotype and phenotype. You’ll hear people talk about genotype and phenotype when they talk about what color a rabbit appears to be and what genes it actually has. Phenotype is the word we use when we talk about what a rabbit LOOKS like. Sometimes the mix of genes a rabbit has will make it look like one color when in reality that’s not what it is. When you’re showing rabbits phenotype is what you’ll be looking at. On the show table, a rabbit is judged on what it looks like and not what genes it carries. You start to worry about what genes it has when you go to breed that rabbit. Genotype is the word we use when we’re talking about those genes and we write it with a string of letters that represent them. We care about it when we breed because it can tell us exactly what genes a rabbit has. And why do we care? Because each rabbit only has 2 copies of each of the genes in its genotype and if we want to get a particular color or pattern our rabbit will have to have the right version of a gene to get what we want. Version? That’s right. Not only are there various genes, but there are various versions of those genes that they can have. We call those different versions alleles. Which of the alleles it has tells us if they can, or can’t, give us what we want. The main genes we’ll be looking at are A, B, C, D and E. They each control some area of color or pattern that will affect what a rabbit looks like.
Each allele controls the outcome of a different set of instructions for color and pattern in a rabbit. When we mix and match them we can get anything from a black rabbit to a harlequin patterned rabbit. Not all alleles are created equal though. In each gene set, there can be dominant and recessive alleles. With a dominant allele, you’ll only need one copy for it to control the color (or “express” itself). With a recessive one, you’ll have to have two copies or the gene will not show through. When there’s only one copy of the recessive we say that a rabbit “carries” a particular trait. One example of that is a black rabbit that carries the gene for chocolate. It’s a black rabbit, but could be the parent of a chocolate baby if paired with the right mate. There is one type of allele that breaks that rule. Those alleles are referred to as co-dominant. They can express themselves when paired with a dominant gene but not as strongly as they would without it. We won’t be getting into co-dominant alleles in this lesson but we will study them in later lessons.
When reading a rabbit’s genotype you’ll often see the set of letters, both capital and lower case ones, with spaces or question marks between them. Dominant alleles are shown as capital letters, recessives as lower case letters and those spaces are there to mark what we DON’T know in a genotype. A good example would is a castor colored Rex rabbit. The color castor (also referred to as chestnut but we’ll talk about that later) is made up of all dominant alleles. Because of that, we would right the genotype as A_B_C_D_E_ . If we know that the rabbit has one dominant and one recessive in the B locus (that’s what we call it’s location on the genotype) we would write it as A_BbC_D_E_. That means that when you look at our castor Rex you won’t be able to tell that it has that recessive b hiding in there because the dominant B will be covering it up. Being able to be hidden like that means that recessives can hide for multiple generations.
And there you have the very basics of how to read and write a rabbit’s color genetics. Just to make sure you caught all the important terms in this lesson I’ll list them out so you can look them over one last time.
- Genotype- the collection of genes a rabbit has, and the string of letters that tells us what alleles it has in that collection.
- Phenotype- what color a rabbit appears to be. This may, or may not, be the same as it’s genotype.
- Allele- the variations of a gene.
- Locus- the various genes and their location in a genotype.
- Dominant- an allele that is dominant over the other alleles in any gene. A dominant gene (allele) will usually make it so that any recessive ones are not visible when looking at an animal.
- Recessive- an allele that is recessive to the other alleles in any gene. A recessive gene (allele) will be hidden by any gene that is dominant over it. Recessive genes can hide for a very long time.
- Codominant- an allele that is only partially recessive to other alleles in its locus. A codominant gene can show through even though it is recessive to another gene.