Genes Behind the Scenes
Posted: Thu Apr 19, 2018 3:55 pm
Video link: https://youtu.be/wV-Dd_ror8g
This week, pups are being born across Yellowstone and beyond. Pups look fairly similar at birth but each one will grow a coat based on its parent’s genetic profile. So let’s take a look at the genetics that determine coat color.
We’ve always had a simple genetics model in the game for puppy coats, but we’re making a much more accurate model now for WolfQuest 3. Genetics has always been a bit daunting for me, but fortunately my neighbor Nathan is a geneticist, and after he explained it to me three times, I think I finally got it.
Most of the wolf’s genome has not yet been analyzed, but in 2009, scientists discovered a gene variant that controls coat color. This got a lot of press at the time because they found that it comes from dogs, many thousands of years ago, meaning that wolves and dogs have cross-bred in the past. They named this gene variant the “k locus.” Every wolf has two copies of this gene which, using standard genetics terminology, is indicated by a small “k” for gray coats or a capital “K” for black coats.
Other genes presumably affect the lightness or darkness of the coat, as well as the gray/brown tint, but these have not been discovered yet. (Genetics is expensive and there’s not a big financial payoff for sequencing the wolf genome.) Keep in mind “white” is tint of gray and is not caused by albinism. Because there have been no known albino wolves in Yellowstone there will be none in WolfQuest (we get a lot of requests for albino wolves).
So the K locus determines the wolf’s coat color:
* If a wolf has two small k variants (e.g. kk), then it has a gray coat (which might be anything from white to dark gray or brown).
* If a wolf has one small k and one big K (Kk), then it has a black coat (since K is dominant). This combination appears to give wolves extra resistance to disease.
* If a wolf has two big Ks (KK), then it is black…but it’s probably also dead, since this combination is usually fatal before birth.
Based on this, we can accurately determine whether a pup will have a black or gray coat, based on its parents’s genes. The Punnett Square is a helpful diagram for figuring this out:
If both parents are kk (both have gray coats), then all their pups will have gray coats: If one parent has a gray coat (kk), and the other has a black coat (Kk because KK rarely survive), then each pup has a 50% chance of being Kk (black coat) and 50% chance of gray coat (kk): If both parents are black and Kk (because KK wolves rarely survive), then each pup has a 25% chance of being KK (black, and probably dying in utero), a 50% chance of being Kk (black), and a 25% chance of being kk (gray): How will this work in the game? We will generate a genetic profile for each wolf which includes the K locus for coat color as well as other genes for coat tint and stats. For the player, this will be based on the wolf’s customization configuration (you choose and then the game generates the genetic profile). For NPC wolves, it’ll be generated dynamically for each wolf, based on Yellowstone’s wolf population (for an accurate distribution of gray and black coats) and standard genetics probablistic rules. So when your wolf meets a potential mate, you can infer a bit about its genetics and decide if you think it’s a good match:
* If you have a gray coat (kk), then choosing a black wolf (which is probably Kk) gives your pups at least a 50% chance to be Kk, and thus have higher disease resistance.
* If you have a black coat (probably Kk, but small chance of KK), choosing another black wolf could give your pups higher disease resistance — but there’s a good chance (25% to 100%) that some pups will die before birth. Litter size in WQ3 will vary (probably between 4 and 7, but we’ll tune that during beta testing), and this risk of a KK pup will add another element of uncertainty to litter size.
It’s very exciting to have this knowledge about the risks and rewards of the K locus so we can model those in the game. We also will include coat tint and stats in the genetics profile, but since scientists haven’t sequenced the genes that control those traits, we’ll use them only to determine those traits on the pup, without any health effects.
And thanks to Neamara for the adorable wolf faces!
Read more about wolf genetics in these articles:
Biologists solve mystery of black wolves
http://newsroom.ucla.edu/releases/biolo ... bout-80301
Heterozygote Advantage in a Finite Population: Black Color in Wolves
https://academic.oup.com/jhered/article ... 57/2961897