Dear Most Esteemed and Knowledgeable Kitties:
I was reading your website and am trying to learn about cat color genetics because it is fascinating. I was wondering if you could help me with a cat color question. If you had a cream and white cat & mated it with a calico cat, would they have blue cream kittens, dilute calico kittens (if there is such a thing) or, what would happen? Also what are some good reads for color genetics? In layman’s terms preferably. I just really want to learn cat colors and am having a horrible time with it. Any advice would be appreciated.
~ Amy
Bella: OMG, y’all, we get to science today! I love science-ing!
Thomas: Yes, helping people understand cat science is super-awesome, so thanks for your question, Amy!
Tara: We can totally help you understand more about cat color genetics, especially when it comes to dilute fur colors.
Thomas: If you’ve been reading Paws and Effect for a while, you know that we’ve written a couple of posts on the basics of fur color genetics. For example, we talked about whether a calico kitten can be fathered by a black and white cat, and we’ve interviewed a college biology professor about female orange cats and how they inherited their fur colors!
Bella: But we haven’t talked much about “dilute” colored cats, such as cream or gray and how they got their colors, so today we’re going to discuss that.
Tara: First, let’s do a quick recap of some basic genetic facts for some background. It all begins with alleles, which are basically alternative forms of a gene that can produce variations in the expression of things like fur color.
Thomas: Alleles can be either dominant or recessive. A dominant allele only needs one copy of itself to show that particular variation of color, while a recessive allele needs two copies of itself to show its specific variation. In the case of full color or dilute color in cat fur, the allele for full color is dominant and the allele for dilute color is recessive.
Bella: Let’s show this in a little contraption called a Punnett square, which shows in a simple way how inheritance of alleles work to create dilute fur colors.
Tara: If you look at this chart, we’ve used the capital D to show the dominant “full color” fur allele, and the lower-case d to show the recessive “dilute color” allele. In this case, mom-cat’s fur color allele is the column on the left and dad-cat’s dilute color allele is the row at the top.
Thomas: Inside the boxes, you can see that if mom-cat has two dominant D alleles and dad-cat has two recessive d alleles, you won’t get any dilute-colored cats. Each of the kittens will have the Dd type, so they’ll show full fur color–remember, a recessive gene needs two copies of itself to display its characteristics–but carry the allele for dilute fur color.
Bella: On the other hand, if mom-cat has one dominant D allele and one recessive d allele, and she mates with a dad-cat that has two recessive d alleles, there’s a 50-percent chance that the kittens will have dilute fur colors. The other kittens will be full-colored because of their D allele, but they will also carry the recessive d allele.
Thomas: And all of this information depends on whether the cat is male or female, because the color allele is carried on the X (female) chromosome. A male cat gets an X chromosome from its mother and a Y (male) chromosome from its father, which means the only color alleles a male cat gets come from his mother. The Punnett square above applies to female kittens because they inherit an X chromosome from both their mother and their father.
Tara: So, will you get dilute-colored kittens if your full-color calico and your cream-colored cat breed? The answer is, “it depends.”
Thomas: You also asked if dilute calico cats exist. The answer to that question is an enthusiastic yes! They definitely tend to be rarer than full-colored calico cats. Most cats that aren’t selectively bred for dilute fur colors (the Russian Blue is one example of a cat that’s specifically bred to pass on the recessive dilute gene) tend to express the more natural full-color state.
Bella: The Punnett square is a very simple expression of a complex concept. There are many genes that influence cat colors, and if we were to make a chart with all of them, it would probably be super-big! But we find that examining one allele at a time makes it easier to understand the concept.
Tara: You asked about books that could help you understand cat genetics. Mama recommends Cats Are Not Peas: A Calico History of Genetics. She thinks it’s an interesting and fun way to dive into cat genetics without being overwhelmed by scientific jargon. However, this book has gotten a good deal more expensive since Mama bought her copy.
Thomas: When Mama was looking around Amazon for books on cat genetics, she found another one that might fit the bill: Herding Hemingway’s Cats: Understanding How Our Genes Work. She hasn’t read that one (yet), but she’s seriously thinking about buying it.
Bella: There are unfortunately not a lot of websites that share information about coat color genetics in a way that won’t make your head spin. But maybe once you have some basic cat color genetic knowledge on board–and we hope we’ve helped by giving you this explanation of how dilute fur colors are inherited from parents–you’ll be able to look at more of these sites and more advanced books for more information.
Tara: Mama wrote a post for Catster a while ago that talks about some of the basic alleles that influence cats’ colors, stripes, and other color variations including dilute fur colors.
Thomas: There’s even a “cat coat calculator” website you can use to determine what kinds of colors your kittens will be based on the color, coat length, and tabby/not tabby status of the parents.
Bella: We hope we’ve helped you understand a little bit more about cat color genetics and what is required to produce dilute fur colors. Please let us know if you have any more questions.
Tara: What about you other readers? Do you have cat color genetics questions? Mama’s a big nerd, and so are we, and we have lots of fun answering questions like this!
JaneA Kelley is a punk rock cat mom and award-winning blogger. She is a regular columnist for Catster Magazine, and she and the Paws and Effect Gang share a home in the beautiful Pacific Northwest.