Why are some dogs small?

Ok. Admit it. You KNOW you have stupid questions that stick into your head from time to time you never bother to seek the answer to. This was one of mine. For whatever reason, the thought came to me when I learned today that most dogs are completely immune to the plague. Did you know that? Me either. Cats are very susceptible to the plague, but dogs are immune. Another stupid fact you didn't need to know.

Anyway, the point of this is Why are some dogs so small? That's the question that bugged me today, and I'll share my knowledge with you. Admit it, you want to know too or you wouldn't still be reading this. Well there are two particular answers, depending on how you're asking it. They are:

1. Why are some breeds smaller than others?
2. How are some dogs "made" smaller than others? (Example: toy dogs)

Well, the answer to number two is simple. Dogs such as the miniature scnhauser are small because they are the mix between the Affenpinchser and the Miniature Pincheser. Mix a medium breed with a small breed and you get a medium-small breed. Mix enough of them and you get a new breed altogether.

The answer to why certain breeds are smaller than others is almost as simple. It relates to a gene mutation in the gene IGF-1, which stands for "Insulin-Like Growth Factor 1" Various genome research institutes including Cornell and the Human Genome Research Institute were looking into this in relation to something else they were doing, but I'm not sure what. Breeds such as the Portuguese Water Dog and other small breed dogs have a mutation in the IGF1 gene that is set to "small". Other breeds, such as labradors, great danes, and other large variety canines have this gene switch flipped the other way... to make them large. Simple huh? All modern dogs are direct descendants of the Grey Wolf, which has the largest setting for this gene. Took all the fun out of it to find the answer.. now I'm off to find the answers to other questions.

Note: It's also been found out that humans that share the IGF1 gene characteristic of smaller dogs are also the smaller of our species... interesting huh?

Technorati Tags: Small dogs,IGF1,Insulin like growth factor 1,canines,history,genome project.