There is no single gene that determines a dog’s size, according to Dr. Ostrander, a canine genomics expert at the National Institutes of ...
There is no single gene that determines a dog’s size, according to Dr. Ostrander, a canine genomics expert at the National Institutes of Health. There are about 25. She and other scientists found the first known dog height gene, and one of the most important, in 2007. It is called IGF1. The importance of the gene has been confirmed in numerous studies. But how this affected the size was unclear.
“The thorn in the side,” said Dr. Ostrander, was that no one could find a mutation in the gene or the DNA segments that controlled it to explain what the actual changes in DNA were that affected height. . “It’s not an exon, it’s not a promoter. It’s not a booster. It’s not a splice site,” she said, referring to sections of DNA that control genes. “We couldn’t find him. And Joc (pronounced Joss) came on the scene.
“And I found it,” he said with a smile.
Dr Plassais, who worked at the NIH during the research and is now at the University of Rennes 1, France, said he had been very fortunate to work at a time when so many genomes of dogs and other canids, both modern and antique, are available. So, by comparing over a thousand genomes from over 200 different races, he found a stretch of DNA that came in two versions, or variants, related to size.
This piece of DNA is not a gene, because by definition a gene must contain the instructions to make a protein. But many other stretches of DNA have the instructions for bits of RNA that help control genes. He found a stretch of DNA containing instructions for so-called antisense RNA, which plays an important role in controlling the production of proteins specified by genes.
His discovery is called IGF1-AS and comes in two variants. Every dog has two copies of this DNA. Two major variations make a large dog, like a German Shepherd. Two small variations make a small dog, like a miniature schnauzer, and one of each makes a medium-sized dog, like one of the world’s ubiquitous dusty-colored village dogs.
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