Before reading this post, you should know how to read a kitty’s genes.
Each trait in CryptoKitties has a “mutation pair” that, when bred together, gives a small chance (usually 14%) of generating a brand new trait not necessarily seen in either parent. Those new traits are referred to as mutations. After a gene mutates, it may then be passed on to offspring the same way as basic traits.
Because Gen 0 cats only have basic traits, mutations tend to be rare at low generations, so they are often (but not always) more valuable.
(Note: Mutations are separate from the “recessive” genes that have a chance to gene swap into the dominant position.)
How do mutations work?
From a technical point-of-view, mutations occur when pairs of neighboring genes (e.g. 00010 & 00011) are bred together. If they mutate, the mutation takes the gene with a ‘1’ at the end and moves it to the beginning (e.g. 00011 –> 10001). You don’t really need to know that, though. You can just use the following method.
In the chart below, you can see that topaz and mintgreen are a neighboring pair. In the right-hand column, it says they mutate into gene ‘i’. Find ‘i’ in the kai column and trace it back to eye color. Topaz and mintgreen have the potential to mutate into limegreen.
To find all possible mutations, please see our updated Trait Chart.
Kitties have four genes for each cattribute. There is one dominant gene (which is expressed) and three recessive genes. When two cats breed, they each pass forward one of those four genes to compete for their offspring’s dominant gene. At that point, there is an opportunity for mutation and the kitten may get an entirely different gene.
First, the parents each pass forward a gene. If they’re neighboring genes, there is a chance for mutation.
Here’s an example. Pretend you have a purebred raisedbrow-eyed cat and a purebred fabulous-eyed cat. (‘Purebred’ means the dominant and recessive genes are all the same.)
Since the parents have the same gene in all four spots, the sire is guaranteed to pass forward the raisedbrow gene and the dame is guaranteed to pass forward the fabulous gene. Fabulous and raisedbrow are neighboring genes and have a 25% chance of mutation to wingtips.* So if you bred these two cats together, you would have a 25% chance of getting offspring with wingtips (and a 37.5% chance of getting raisedbrow, and a 37.5% chance of getting fabulous).
But what if the parents were NOT purebred? What if their genes looked like this?
A cat has a 75% chance of passing forward its dominant gene, so there is a 75% chance this sire will pass forward raisedbrow and a 75% chance this dame will pass forward fabulous. Provided that happens, there’s a 25% chance they will mutate at that point.
0.75 * 0.75 * 0.25 = 0.14 = 14% chance of wingtips
What if you don’t have a fabulous-eyed cat? But you do have a simple-eyed cat with a fabulous recessive gene?
The probability that the simple-eyed cat will pass forward the fabulous gene (R3) is only 1.5% (see chart below). So the odds of getting a wingtips from this pair is…
0.75 * 0.015 * 0.25 = .0028 = 0.28%
In other words, very, very small.
BUT IT HAPPENS SOMETIMES! In fact, this is exactly how the first elk was created!
You can use a breeding calculator to calculate all the probabilities for you (like KittyCalc or KittyAppX). If you want to find out the odds of getting two or three traits simultaneously (like when breeding a fancy), just multiply the probabilities together.
*NOTE: The chance of mutation is 25% for low-tier traits only (kai codes 1 through p). When we start mutating mutated mutations (genes q through x), the chance of mutation will only be 12.5%. See the right column in the Trait Chart for details.
The odds of a cat passing forward a gene is:
A big shout-out to Poopie.Cat and AppX Matthew for creating the breeding calculators!
Also, thank you to @AlanFalcon for contributing to this post.