Mutt Mixer shows traits where single genes have big effects. In wild species, it’s rare for a gene to have so much influence. But it’s more common in species that humans have shaped through artificial selection, like dogs. That’s because people over the years have chosen dogs with interesting and unusual trait variations to breed. Dogs with those traits today are descended from a few individuals.
Single genes with large effects on traits are rare. Much more commonly, trait differences come from many genes, each with a small effect, plus factors from the environment.
Dog traits aren’t just cute. Geneticists can study their traits to learn how they work at the gene and protein level. Then they can extend this knowledge to understand similar traits in more complex populations, like people.
Dogs and people, for example, have many of the same diseases—like cancer, diabetes, and arthritis. These are complex diseases that involve many genes plus factors from the environment. In people, the gene variations involved can vary a lot between individuals. That makes it hard to track down genetic risk factors for these diseases. But often in dogs, as a side effect of artificial selection, there are fewer genes involved. This makes it easier to find disease genes in dogs. And sometimes the same genes underlie the same diseases in people.