05-07-2022, 10:16 AM
Guide to Cat Genetics
Overview
Genetics are confusing on their own, and cat genetics are even more so. This guide aims to help break down and make it easier to understand natural cat genetics for any character you may create. There won't be long scientific rambles, don't worry! I will explain the terms and the process of reaching the genetics you want, so buckle in and grab a pencil.
Genetics is what makes every living creature have different traits and different looks. Gregor Mendel realized this and began his work on discovering how these traits are passed down and how they cross-breed. Mendel is why we can breed animals and plants to have desirable characteristics or breed negative ones out. He coined most genetic terms and is still referenced by scientists who work with genetics. But, we aren't here to have a seminar on Mendel and how he discovered all this. We're here to dive into how it applies to cat genes.
So, let's start with the terms!
Terminology
▻ Heredity - The passing of traits from one generation to the next.
▻ Genetics - The study of Heredity and the passing of traits.
▻ Mono-Hybrid - An individual or strain heterozygous for one specified gene.
▹ Mono-Hybrid Cross - This is usually homozygous dominant and homozygous recessive
▻ Alleles - The variant form of a gene.
▻ Homozygous - Having two identical alleles of a particular gene or genes.
▻ Heterozygous - Having two different alleles of a particular gene or genes.
▹ Dominant Allele - If the alleles of a gene are different, one allele will be expressed (determined) as the appearance; it is the dominant gene.
▹ Recessive Allele - The effect of the other allele, called recessive, is masked. Only is expressed when both alleles are recessive
▻ Phenotype - Refers to an observable trait, like hair, fur color, eye color, etc.
▻ Genotype - The genetic makeup of an organism. Ex: BBGGDD {B=Black G= Gold D= Dense}
▻ Dihybrid - A hybrid that is heterozygous for alleles of two different genes. Usually heterozygoud breeding.
▻ Complete Dominance - One allele is dominant and the other is recessive.
▻ Incomplete Dominance - When a dominant allele, or form of a gene, does not completely mask the effects of a recessive allele. A blend of both alleles.
▻ X-Linked Gene - The gene causing the trait or the disorder is located on the X chromosome. Not epressed the same way in males and females.
Breaking it Down
This is where it gets a tad complicated, depending on the cat's coloring. I'd suggest taking notes; that way you can have these in shorthand and easier to access. Now, you can use any letter in the alphabet, except x, for genetics. When you the letter "x," you have another letter than follows.
Now, let's try a simple punnet square.
Phenotypes: Purple Flower x White Flower
Genotype: PP x pp
The punnet square is set up as follows: the upper part is the mother's traits, which is "pp," and the left side is the father's traits, which in this case is "PP." Now, we're going to cross them.
"PP" is Homozygous Dominant. "Pp" is Heterozygous. "pp" is Homozygous Recessive.
Now, back to what we're here for, cat genetics. Let's say we're figuring out the genetics of a black cat with a red tabby cat. The tabby gene will be defined later, but we will disregard it for now. So, during the split of a cell, in Meiosis, the sister chromatids do something called crossing over. The two exchange alleles before becoming a single gamete. A gamete is a single trait, which would be a single letter. This letter signifies dominance or not.
First, we'll create a key:
x[sup]r[/sup]x[sup]r[/sup] = red female
x[sup]B[/sup]x[sup]B[/sup]= black
x[sup]r[/sup]y = red male
x[sup]B[/sup]y = black male
x[sup]B[/sup]x[sup]r[/sup] = tortie
D = dense
d = dilute
We now separate each gamete from the other.
X[sup]B[/sup]Y = black male
x[sup]r[/sup]x[sup]r[/sup] = red female
For our first punnett square, we will not worry about whether or not a cat is dilute or dense. For now, we create a Four-Square punnett square.
We get three unique genotypes:
x[sup]B[/sup]x[sup]r[/sup] = black tortie female
x[sup]B[/sup]Y = black male
x[sup]b[/sup]Y = red male.
This is a simple way, but we get more complex as we break down two or more factors. The genotypes above were one of the most difficult of the genotype break down. That was the X-Linked Genotypes. The non-linked are called autosomal; this is when gender doesn't play a factor. Remember the flower punnett square? That one is autosomal. So, we've done two types of punnett squares: X-Linked and Autosomal.
We will use our key from before:
x[sup]r[/sup]x[sup]r[/sup] = red female
x[sup]B[/sup]x[sup]B[/sup]= black
x[sup]r[/sup]y = red male
x[sup]B[/sup]y = black male
x[sup]B[/sup]x[sup]r[/sup] = tortie
D = dense
d = dilute
Now, we'll assume that both are Heterozygous for dilute. This will give us more variations within our new genotypes and a bit more of a challenge.
We have a dense black male and a dense red female. Both are Heterozygous for dilute. This means that both carry dominant and recessive. The dominant just shows up as the larger lettering of the to and is often the trait that is carried, unless it is certain X-Linked, codominant, incomplete dominance, complete dominance traits.
Now, the father is going to be black and the mother a black tortie. The father carries no white spotting and neither does the mother. The father is Homozygous for dense and the mother Heterozygous.
So, we begin crossing these. We pair the genes with each other; we need four down and four across. It can get tricky here.
The phenotypes are the easy part, these are the physical appearances.
Phenotypes of Black Male x Black Tortie
Females: black female homozygous dense, black female heterozygous dense, black tortie homozygous dense, black tortie heterozygous dense
Males: black homozygous dense, black heterozygous dense, red tabby homozygous dense, red tabby heterozygous dense
Coats and Coloration/Genotype
▻ Black
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![[Image: white_spotting.PNG?width=1181&height=541]](https://media.discordapp.net/attachments/901386501366112306/971675188339040297/white_spotting.PNG?width=1181&height=541)
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![[Image: pcmr_723_f1.gif]](https://onlinelibrary.wiley.com/cms/asset/17ce94db-8f7c-401b-8fe0-f982428ec4fb/pcmr_723_f1.gif)
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You don't have to do any squares for these since that'll be too much, but if you want a character to have any hereditary disorders or disabilities, take a peek at the links.
Most Common/Important
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I adapted the FeralFront post into this; I either rewrote parts or cut out some useless text. I made the punnett square images! I think it's easier to understand with visual aids, and it helps to be able to see how we get the results we got. I'll have links to the templates I used/made easier to write on. Everything else is things I used images from and my own sources. The link to more genetics info is from the FeralFront post. I consider the links for the disorders/disabilities section not needed to be re-linked. Agouti, White Spotting, and Tabby are better to be looked up, as I cannot give perfectly accurate information on how those are carried down; I can estimate and guess, but I cannot give solid answers for those.
FeralFront Master Genetics Post
Some info from CFA
Messybeast, I love this site! Would recommend it heavily!!
Links to more genetic info if you so wish
More basic genetics
More Coat Genetics
8 Punnett Square Template
4 Punnett Square Template