The Genetics of Dogs

A corgi smiling for the camera.


Notes

Evolution of Dogs Explained by Neil deGrasse Tyson (5:10)


Before watching this video, think about what effect thousands of years of domestication would have on the ability of dogs to solve puzzles.

Wolf vs. Dog Intelligence Test (2:46)



The selective breeding of dogs has created animals that are very different from their ancestors. There is a series of "dogs then vs. dogs now" memes that make fun of this fact.

It is fairly well-known that any non-corgi dog crossed with a corgi will produce a child that looks like a corgi disguised as a non-corgi.

All dogs (and humans) have a gene called fibroblast growth factor 4 (FGF4). However, in corgis, this gene has been copied to another location in their genetic code, creating what is known as a retrograde gene. Due to years of selective breeding, almost all corgis now have two dominant alleles of this retrograde gene, in addition to 2 dominant alleles of the original FGF4 gene. For complex reasons, having extra copies of the dominant FGF4 allele causes dog legs to grow less.

As a class, we will draw out the (very simple) Punnett Square for a corgi mating with a corgi. We will use F to indicate a dominant allele of the extra FGF4 gene, and f to indicate a recessive allele.



F
F
F
      
      
F


In this case, we see that every possible child has an FF, meaning that the child would express short legs.

As a class, we will draw out the (very simple) Punnett Square for a corgi mating with a German shepherd dog (GSD). We will use F to indicate a dominant allele of the extra FGF4 gene, and f to indicate a recessive allele.



F
F
f
      
      
f


In this case, we see that every possible child has an Ff, meaning that they will express short legs.


Questions


  1. Make the Punnett Square if you decided to breed a corgi-GSD cross with another corgi-GSD cross.
  2. Look at this picture from Popular Science. Can you explain the F2 generation (labelled 5 to 11), using the results from your previous question?
  3. Why do you think most dogs can smile?
  4. What ethical concerns are there with breeding dogs selectively?