For those traits, instead of getting the direct value from one of the parents, we wanted to build a more complex genetics system that reflects simplified dominant/recessive models that are already documented in real life. These are the only traits that are able to “skip a generation”!
How it works:
We built a simple system of genes and alleles to simulate how these features are passed down. Some traits are dominant, meaning they only need one copy of the gene (allele) to appear (like brown eyes). Others are recessive, which means they need two matching alleles to show up (like blue eyes). I already talked a little about the two-gene model for eye color in this very old post, but here is another example that we implemented for hair texture.
There’s one gene for hair texture, and it can have four possible alleles: straight, wavy, curly, or coily; with coily being the most dominant, and straight the most recessive. In other words, the more curls you have, the more likely the trait is to “win” when mixed. Let’s say a Para gets one curly allele from their mom and one wavy allele from their dad. Since curly is more dominant than wavy, the Para will have one of our curly hairstyles, chosen at random. But the wavy gene is still there, and it could show up again in their child, if paired with another recessive allele!
In this example, the mother’s hair is coily and the father’s hair is straight. In genetics terms, the dad has to have (Straight/Straight) alleles, since straight hair is never dominant. Since the kid has curly hair, it means his mom has (Coily/Curly) alleles and he has (Curly/Straight) alleles.
One curly grandpa or grandma would have been very proud!