Leslie A. Lyons, an associate professor at the University of Missouri School of Veterinary Medicine and Surgery, is a leading expert on comparative genetics. She specializes in cats and was not only kind enough to host a special expert forum on feline genetics here on TCS, but also agreed to answer more questions in a special interview.
Like so many of us, Prof. Lyons grew up surrounded by family cats, but she says she had never thought she would end up studying them. She began her academic career studying Chemistry and Biochemistry at the University of Pennsylvania. Keeping veterinary school in her sights, she took a genetics class in her third year of college and found her calling. After receiving her PhD in Human Genetics, she decided to switch to Comparative Genetics and focus on studying other species.
"When I went for my post-doctoral fellowship," Prof. Lyons told me, "I interviewed with a fish person, a cattle person, a cat person and... ended up working on cats because I picked a big lab that had good ties to human genetics. So I didn't pick cats because of cats, but I picked them because of the lab. In the end it’s really your post-doctoral fellowship, not your PhD work, that creates your career. Once I started working on cats in February 1992, I just never looked back. That became my niche and that’s how I started."
Kitties Have Pretty Chromosomes
According to Prof. Lyons, all mammals have pretty much the same genetic makeup. Mammals, whether cats, dogs or humans, all have approximately 21,000 genes and approximately 3 gigabytes worth of DNA. Our chromosomes are the vessels where these genes are held. The number of chromosomes we have and the way the DNA matter is distributed on them is what sets us apart as different species. Cats have 18 pairs of chromosomes, while humans have 23 pairs. Why the difference in the number of chromosomes? I asked Prof. Lyons that question.
"That was kind of an interest of mine in the beginning, too," She replied. "If we look at the chromosomes of the cat, they are very good representatives for all carnivores. There are lots of different types of carnivores, including dogs. But if you look at dogs, they have 38 chromosome pairs, all shuffled and mixed up in little bits and pieces. Why? Why would that happen? What does that do differently as far as making a species survive? A dog has a very mixed-up genome, whereas a cat’s genome is very very similar to a human genome as far as its arrangement."
I asked Professor Lyons if this meant cats were more similar to humans than dogs, genetically speaking.
"Unfortunately, no", she chuckled in response. "Just from the chromosomes - yes. But if we look at the sequence of every gene, the sequence between a cat and a dog is going to be 95% the same. The sequence between a cat and a human or a dog and a human is going to be about 80% the same." She did however add that cats "definitely have prettier, better-looking chromosomes." So there you go. We all know our cats are pretty on the outside, but now we know they have pretty chromosomes, too!
Whiskers on humans? We have the gene for it!
Since we share so much of our DNA with cats, how come we look so different? That's because genes are peculiar things. The exact same gene can do entirely different things in an organism, depending on how and when it's turned on and off. Prof. Lyons explained this using the gene for whiskers as an example.
"This is an androgen receptor gene. All mammals have it, but there are different control elements. Above the gene, before you get to the gene itself, there are kind of start and stop sites that say, “Ok, turn this on, turn this off” and “Here’s when you turn this on and here’s when you turn this off”," she said.
In most mammals this gene is switched on to create proteins that build up the animal's whiskers. It also affects, ahem, the penis. You may know that the penis in a tom cat has spines on it? Yup. Spines, or pointy little barbs. When cats mate, as the male cat pulls out his penis, the penile spines scratch the female's vagina and this causes the female to ovulate, enabling fertilization. So, if we have the very same gene, how come humans don't have whiskers and penile spines?
"The difference between cats and us is that we’re missing one of those start/stop sites," Prof. Lyons revealed. We have the gene and it creates receptors for hormones in humans, too, but fortunately, the different start/stop sites mean it does not send the downstream signal to produce whiskers or penile spines. Whew!
Tabbies with White Lockets and the Domestication of Cats
"Everything you need to learn about genetics – you can learn from your cat," was the name Prof. Lyons had suggested for the expert forum she hosted here at TheCatSite.com. Indeed, even when speaking about her own cats, we ended up discussing the genetic aspects of feline domestication.
But first things first, allow me to introduce Withers and Figaro, the resident Lyons cats.
"My own cats are 12 and 13 years old," Prof. Lyons said. "The mother, the black cat, is called Withers. The first cat I can remember as a child that my family had was Withers and it was black with a white locket. Once I had moved to California, I didn't have any cats at that time and I thought, 'Well, next cat that comes along that’s black and has a white spot, that’s gonna be mine'. I saw this cat in the nutrition colony [at the UC Davis genetics lab] and it needed a home, and so I took Withers. Then I let Withers breed, which is somewhat not so good and she had only two kittens. One kitten later died, several months down the road. I still had the one female kitten, and I did spay her before she bred, and that’s Figaro."
Withers is black with a white locket, but Figaro is a brown tabby with a white locket. According to Prof. Lyons, that's quite a symbolic combination when it comes to feline genetics.
"Brown tabby cats are what we would call the wild-type cat", she stated. "This is just what a normal cat is supposed to look like. White spotting is one of the first genes you start to recognize when animals are domesticated. So, you look at Figaro and you say, that’s a perfect wild cat there, except look at that little white spot, telling us she’s a domestic kitty."
Genes related to domestication is a fascinating topic so I asked Prof. Lyons to explain some more.
"People would like to start to understand the genes involved with domestication", she said. "Certainly there are going to be genes involved with behavior. What made a wild cat decide, 'Wow, if I start to tolerate humans, and I get close to them, I can get pretty easy meals, because there are all these mice around the grain stores.' And that’s probably how cats domesticated themselves. The individual cats that had that little genetic change that said 'I’m not going to be as frightened' became the domestic cats."
When I asked her if those same behavior-affecting genes could be related to the white spotting, Prof. Lyons replied that it's a possibility that still needs to be fully researched: "We don’t know just yet and we try to figure it out. What we have to keep in mind is that genes on different chromosomes pretty much act independently, but genes that are on the same chromosome and live pretty close together, they work in tandem. So maybe a gene that’s involved with behavior might be right near the genes that control white spotting. That’s how something like that would happen."
Click to continue to part 2, where Prof. Lyons talks about existing genetic tests for kitties and explains which diseases you should be looking for in each breed and why.