Corgis: The Genetics Behind a Loaf on Legs

Corgis. They’re short. They’re compact. And they have the most beloved butts on the internet. It’s hard to imagine how the lovable little dwarf pooches could have the same common ancestor as the wolves that terrorize fairy tales.

from American Kennel Club

It’s been common knowledge for thousands of years among humans that you can breed species of animals and plants in a way that selects for specific traits. It’s how corn transformed from a gross, starchy cobb to the sweet, golden vegetable it is today. It’s how wild mustard evolved into broccoli.

It’s easy to see that traits are inherited. It’s pretty common for a child to hear that they have their mother’s eyes or their dad’s hair. Pick two members of a species that look similar, their offspring is probably gonna share their traits. So, in order to get a tall, muscular dog, down to a short, stubby dog like a corgi, they just had to continue to pair dogs that happened to have shorter legs with each other. This would’ve taken a while, but we got there. It’s a big easier these days to make “designer” dogs since we now have plenty of different traits to choose from. Just look at this Golden Dox.

The reason we’re able to make such unique breeds is all thanks to mutations. Mutations are how new traits can pop up in a population. Now, most of the time when someone says the word ‘mutation’ they’d probably think of the X-men or snakes with two heads. In reality, most mutations aren’t even visible.

A mutation happens when there’s a typo in the code in your DNA. If you think about it in terms of sentences, a small error won’t really affect your ability to read it. For example, the small cat rtn down the street. There’s an error, but it’s still understandable. Now imagine a larger mutation: te smlllc dnwt sttttt. Not really legible. Large mutations like that are very rare. However, a small mutation that results in say…a slightly shorter dog than usual would be more likely.

There’s a bit more to the genetics than that, but you get the basic idea. Next time you look at the adorable behind of a Corgi, think about all the generations of new mutations it had to go through. It’s tough work becoming that cute, and unfortunately a lot of our selectively bred dogs have health problems. Part of it comes from the weird new shapes these dogs sometimes take (Corgis inherited back problems), but most of it comes from having a really small gene pool. Genetic variation is a good thing. It allows new healthy genes to enter the population. No variation means you’re stuck with the same possibly crappy genes until a mutation occurs–and there’s not telling whether it’ll be a good one.

So keeping all that in mind, what is the right thing to do? Should humans continue to use selective breeding? We’ll continue to get new, even cuter animals, but they might have health problems because of it. On the other hand, selective breeding has created some pretty tasty crops and we’re able to sustain a large population because of it. But it also raises the ethics issue of designer humans. Let me know what you think. And if you want to learn more, or just review, check out the video below.


For the educators: This week’s blog post was a challenge issued to us to pick an NGSS topic and persuade a student to care about it. I decided to focus on Corgi’s because they’re cute, they’re all over the internet, and I know my middle school sister and her friends are obsessed with them. It was a safe bet they’d be interested.

In case you were wondering, here are the standards that the Corgi lesson was based on:

NGSS LS4.B: Natural Selection
In artificial selection, humans have the capacity to influence certain characteristics of organisms by selective breeding. One can choose desired parental traits determined by genes, which are then passed on to offspring.

Students who demonstrate understanding can:

MS-LS3-1. Develop and use a model to describe why structural changes to genes (mutations) located on chromosomes may affect proteins and may result in harmful, beneficial, or neutral effects to the structure and function of the organism.

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