The making of a tabby cat

I’ve found it quite fascinating to look into cat genetics over the past week. I should have my entire planned activity for my bio students to share by next week, but in the meantime I thought I’d write about the agouti and tabby genes.

The presence of a dominant agouti gene affects pigment distribution along the hair shaft. You can see in the photo below that there are bands of dark and light pigmentation. As an aside, taking a clear photo of a single hair is not an easy task.

A recessive, non-agouti individual would have hairs that were a single colour.

To make things a bit more interesting the gene for tabby patterns (there are multiple tabby alleles which result in different patterns) affects the timing of when the agouti allele is expressed. This is one form of something called epistasis. Epistasis is the fancy word (there’s a lot of those in biology) for a situation when two or more genes affect a single phenotype (the observable characteristics) but the don’t just add together. They could create new phenotypes, one could mask the effects of the other, or one could modify the effects of the other. This last one is what happens between the tabby gene and the agouti gene.

I don’t know about you, but I think it is amazing how everything interacts with each other. The fact that the tabby gene will affect when the agouti gene has an effect is absolutely fascinating. For the purposes of the activity I’m building, my students will just use the presence of a tabby pattern to determine whether or not there is an agouti allele present rather than get into all the specifics of the tabby pattern, but the tabby alleles are pretty interesting too. Perhaps I’ll investigate them for a post in the future.

So I leave you with a photo of one of my two cats, the one who is currently watching the words appear on the screen as I type. She graciously donated the hairs for the photo above so it seems only fair to also show her in all her tabby cat and agouti hair glory.