One of the main genetic variations responsible for small size in certain dog breeds evolved in dog relatives long before humans began breeding these miniature companions. wolves that lived more than 50,000 years ago can be traced back to the source.
The National Institutes of Health (NIH) Dog Genome Project, a citizen science project in which owners collect DNA from their dogs, is where researchers discovered the IGF1 genes.
This rare and unusual genetic change, found not in the IGF1 gene itself, but rather in the genes that regulate its expression, had previously evaded researchers for over a decade.
After consulting with scientists in England and Germany, the researchers found that the variation was present in 54,000-year-old DNA from the fossils of Siberia wolves, as well as in the DNA of every canid species alive today.
The 10 most popular dog breeds.
It is as if nature kept it in her back pocket for tens of thousands of years until it was needed.
She said that the discovery helps tie together what we know about dog domestication and body size.
The blueprints for the construction of specific proteins are contained in genes. Adenine, guanine, cytosine, and T are the four bases that make up each of the genes. Cells need to read the bases of the strand that contains the corresponding genes in order to make a specific protein.
A single-stranded molecule similar to DNA with one different sugar is created by special machinery within the cell. This process is called transcription.
The body size of the dog is influenced by the expression of the IGF1 gene, which is located in a section of DNA. There are two versions of the same piece of DNA, one with an extra cytosine base and the other with an extrathymine base.
She said that each dog can have either two versions of the small allele or two versions of the large one.
Small dogs were CC, medium-size dogs wereCT and large dogs were TT, according to the researchers, who looked at the DNA of different dog breeds.
The canids have become smaller due to the IGF1 abnormality. Plassais et al., Current Biology, 2022.
The researchers wanted to know how far back in the evolution of the alleles that they could find in ancient wolves.
We were surprised to find the C and T variant, which was present over 54,000 years ago.
She said that the researchers had predicted that the allele for smaller stature was newer than the one for larger size.
The evolution of smaller canids such as jackals, coyotes and African hunting dogs, all of which have two copies of the small allele, appears to have been aided by the IGF1mutation. She said that it is unlikely that small dogs would have evolved to become as small as they are without the intervention of human domestication and breeding.
The small allele was maintained at a low level in dogs for tens of thousands of years until it was selected on during or around the time of domestication.
She said that the breeding was done to create smaller dogs that could hunt rabbits.
The first slightly smaller dog breeds, which were eventually bred into the extremely miniature versions we see today, emerged between 7,000 and 9,500 years ago, according to the researchers.
There are other genes that affect a dog's body size. There are at least 20 known genes that code for body size, but this particular one has an outsize influence: It is responsible for about 15 percent of body size variance across dog breeds, a large amount for just one gene.
Hundreds of genes affect body size in humans. Most dog breeds have been around for only a few hundred years, so it is unsurprising that dogs have less body-size related genes.
The researchers will continue to study more body-size genes in dogs to better understand how the genes work together to determine the exact size of every breed.
The next step is to figure out how all the genes work together to make dogs.
The study was published in January.
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The article was published by Live Science. The original article can be found here.
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