A Crash Course in Genetics
Roots of Life is a genetics-based RPG. This means we follow real-world genetics. We strive to be accurate to real-life genetics science, including new discoveries.
Learning about genetics can be intimidating at first, but it's a lot easier to learn once you know the basics. This is a guide for that!
To start you off, here's some vocabulary:
Phenotype: Your cat's appearance. ex. a solid black cat with long fur!
Trait: A trait is the word for a part of a cat's appearance. ex. "black fur" is a trait, and so is "long fur".
Genotype: A list of all of your cat's genes.
Gene: Every trait you see (like fur length and color) has a corresponding gene. A gene is the actual genetic code that determines how your cat looks.
We write each gene as a few letters, for simplicity.
Genes themselves are a combination of alleles and loci.
Allele: Each gene is made of two alleles. The alleles each code for a trait. There can be more possible alleles than can fit on one gene. Each allele is written as 2-3 letters.
Locus: All alleles belong to a locus, the location in the genetic code where the alleles live. The plural form is loci.
Thus, genes are like larger categories of traits, which are considered related if they belong to the same locus. What combination of alleles you put onto a locus determines the gene that you get.
That's probably a bit confusing, but it's time for an analogy!
You need to pack some shirts for a trip. For one reason or another, the box you have can only hold two items. But you have more than two items! You have two red shirts, and two blue shirts. So what kind of box do you make?
If you put two red shirts in your box, it would be a red shirt box. If you put in two blue shirts, it would be a blue shirt box.
What about if you put in a red and a blue shirt? Well, maybe you get a purple shirts box! Or... maybe you get a red shirts box, still? Wacky! I'll explain.
Genes, loci, and alleles work like that. A locus is like a box. Alleles are like all the possible items you could put in that box. Each allele codes for its own trait, and multiple alleles together make the final gene (aka the final box).
How you know what the final box will be depends on if each allele is dominant or recessive.
Dominant: Dominant traits will cover up other traits.
Recessive: Recessive traits will be covered by other traits.
So for our box, if red is dominant over blue, our final box will be a red shirts box if any red shirts got added to it. In genetics lingo: if we have any red shirt alleles on our shirt color locus, we will get a red shirt gene.
Dominance and recession are relative, so Trait B can be dominant to Trait C, but recessive to Trait A. For a more relevant example, the colors black, chocolate, and cinnamon work this way in cats. Black fur is dominant over all the others. Chocolate is dominant over cinnamon, and recessive to black. Cinnamon is recessive to both other colors!
That's not all, though; co-dominance is also a thing.
Co-Dominance: Where two traits are equally dominant, and will co-exist if present at the same time. This is sort of like mixing red and blue to get purple, from our earlier example.
The traits colorpoint, mink, and sepia work like this in cats. Only colorpoint and sepia have actual alleles -- cs and cb, respectively. When combined (cscb), they create mink! Pretty cool!
Finally, two last terms for you:
Homozygous: A gene's two alleles are the same.
Heterozygous: A gene's two alleles are different.
Cats with heterozygous genes are also known as "carriers" of the trait they have but don't display. For example, a black cat with the gene "Bb" carries chocolate (B = black, b = chocolate).
Sometimes only having one copy of a gene gives a trait a slightly different look, so that's the reason you need to know this.
This knowledge should get you through learning most of RoL's genetics system. Good luck! If you have any questions, our staff love talking genetics and are always happy to help.