Recently researchers led by Erik Axelsson at Uppsala University in Sweden conducted a survey of dog and wolf genome sequences (all of an organism’s DNA in order) looking for evidence of genes involved in domestication of dogs from wolves. When comparing the two genomes, researchers used some head-spinning statistics and key database-driven tools to identify regions of DNA that show signs of encoding traits for which natural selection and human breeders selected as wolves and humans interacted more often. Calling these regions “candidate domestic regions” (CDR’s), they used a database equivalent of looking up genes in those regions on Google, finding that many fit neatly into the following categories: nervous system and development, sperm-egg recognition, regulation of molecular function, and digestion. This database-searching tool is called “Ensembl”, and is available at http://useast.ensembl.org/index.html. You will need to know the name of a gene to get started, so try this one out: AMY2B. In the search results, find "dog", click on the link next to "Gene ID", and see the sidebar for information regarding the gene.
In all, they identified 36 CDR’s containing 122 genes. In this particular study, the researchers chose to focus on AMY2B, MGAM and SGLT1, genes related to starch metabolism. The researchers report evidence for the influence of selective pressure, finding significant genetic change in these genes in dogs as compared to wolves, including: increases in the number of copies of each gene, a greater frequency of mutation in each compared to surrounding genes, and higher expression of each in dogs.
Axelsson and his team conclude that “dog domestication was accompanied by selection at three genes with key roles in starch digestion: AMY2B, MGAM (our gene of interest) and SGLT1.” Further, they suggest that “adaptations that allowed the early ancestors of modern dogs to thrive on a diet rich in starch, relative to the carnivorous diet of wolves, constituted a crucial step in early dog domestication.” As more of such studies contribute to the complex process of dog domestication, researchers may be able to claim starch metabolism as the most prominent feature of the process. Until then, these findings make a strong case for it playing a major role.
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