[News] All Dogs Great and Small: Scientists Discover The Gene That Controls Dog Size

[fasteddie]

Despite the huge variation in body size and shape, Great Danes and Chihuahuas are both members of the same species: Canis lupus familiaris. They retain the ability to breed with one another (allowing for a certain amount of gymnastics) and produce viable offspring. No other species that I can think of contains such a diversity in body size?almost two orders of magnitude between the smallest and largest.

Now, a new study conducted by an international team of scientists led by researchers at the National Human Genome Research Institute (NHGRI) has identified the gene responsible for this great range of dog sizes. The answer, it seems involve a number of different versions of the gene that encodes for insulin-like growth factor 1 (IGF1). The gene, IGF1, was identified following genetic analysis that began with screening 463 Portuguese water dogs, a breed that has a lot of diversity in size. The researchers measured the dogs, took X-rays, and then sequenced their DNA and looked for different regions of interest.

It turned out that a number of single nucleotide polymorphisms (SNPs) where one base pair is altered in a sequence, located close to the IGF1 gene, correlated strongly with changes in body size. Next, the team extended the study to take in more than one breed, and looked at DNA from 526 dogs across 23 small and 20 large breeds. The genetic analysis identified IGF1 polymorphisms as the common factor in determining size. Small dogs were much less likely to contain two different versions of IGF1 compared to large dogs. The fact that many small breeds of dog are only distantly related suggests that the different versions of IGF1 arose early in the domestic dog's lineage, and were selected for by dog breeders attempting to obtain a certain look.

Studies in mice and clinical reports in humans have previously identified IGF1 as being involved in determining body size, with IGF1-deficient mice being around 60 percent normal size. This research team will plans on turning their attention to identifying genetic markers that control other aspects of canine appearance. Whether they find the gene for adorable remains to be seen. The study will be published in Science tomorrow.

http://arstechnica.com/journals/scie...trols-dog-size

[blackwidow]

Whether they find the gene for adorable remains to be seen.

Then they should be studying Yorkies!!