Not That Size Matters

There's something mysterious about dogs. It's not normal, from the point of view of the rest of animals that, within the same species exists such huge variation in their size. They are mammals with the biggest difference of stature, and the fact that such a great variety of them cohabit, from the smallest like Chihuahua to the biggest as Saint Bernard, has always fascinated the scientists. In human version, a Chihuahua would be like a human adult of half a metre in height, while a Saint Bernard would be one and a quarter metre.

A group of American scientists seemed to have found the key factor to explain such diversity in size of dogs. According to an old magazine I found, 'Science', it published that all the dogs of small breed, shared a part of the mutation of their DNA, situated in the chromosome 15, on the regulated sequence it's on the side of IGFI (whatever that is I haven't a clue), which produces the kind of hormone of growth in dogs, as well as in rats or humans. What the regulated sequence does is diminish the effect of the gene IGFI, in the way that those dogs that have the mutation would have their growth limited. It works like the bandage put on women's feet in ancient China, impeding the normal growth of the extremities.

The big dogs also have the gene IGFI, but in their case, there's no mutation, so the hormone of growth acts normally. Some other genes not yet identified are also implicated in large breed of dogs.

The participating scientists in this study, led by the University of Utah, had analysed the DNA of more than 3,000 dogs of 143 breeds. At that time, they had not identified the exact mutation in the regulating sequence of the DNA which reduces the effect of the gene IGFI, but they had found small pieces of genetic material to serve as model, to locate causes of diseases like diabetes, cancer or arthritis. They said future investigation would centre on identification of genes related to the dog's behaviour and diseases.

That magazine is 6 years old. I guess by now they have learned a lot more. I hope nobody tries to interfere and change their vastly different sizes, whatever else they do. Variety and differences in animals, as well as in human, make the world far more interesting.

Yeap, the little one too is a dog!

Tags:Chihuahua,SaintBernard

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