Dog Genome Shows Human Influence
Dec. 7, 2005 â€” Scientists unveiling the genome of the dog on Thursday say that Rover’s DNA blueprint bears the heavy mark of human influence, transforming a rough, gruff descendant of the wolf into the sleek, pampered pedigrees of today.
The tissue sample that was used to decipher the canine code came from Tasha, a female boxer â€” a breed whose prominent jaw and labored breathing bear witness to human selection among dogs.
Publishing the sequence of the domestic dog (Canis familiaris) in the British journal Nature>, the U.S.-led group say the history of the hound “traces back at least 15,000 years, and possibly as far back as 100,000 years, to its original domestication from the gray wolf in Asia.
“Dogs evolved through a mutually beneficial relationship with humans, sharing living space and food sources,” they say.
The team, led by Kerstin Lindblad-Toh of the Broad Institute of the Massachusetts Institute of Technology (MIT) and Harvard University, sequenced 2.4 billion DNA “letters,” accounting for 99 percent of the canine genetic code.
Dogs have 39 pairs of chromosomes, although in this case the “Y” chromosome, found in males, was absent as the dog was female. By comparison, humans have 23 chromosome pairs.
The gene team also took samples from another 10 breeds with the idea of comparing genetic differences and drew up a catalogue of “snips” â€” single nucleotide polymorphisms, or one-letter changes in the genome that could explain different canine behavior and vulnerability to disease.
Over thousands of years, genetic pressure by Homo sapiens caused the emergence of dog breeds that specialized in herding, hunting and obedience, as well as dogs prized for certain looks.
This “evolutionary experiment” has produced more breeds of domestic dogs than for all other members of the Canidae family, the classification for dogs that encompasses wild as well as domestic dogs.
There are estimated to be 400 million dogs in the world today, and around 400 modern canine breeds.
Stringent inbreeding in the search for genetic traits has also inbred the risk of disease, such as cancer, blindness, weak hearts, cataracts, epilepsy, arthritic hips and deafness.
Several hundred genetic disorders experienced by dogs are also shared by humans.
Pinpointing the genetic causes in dogs may also help humans, encouraging diagnostic tools which spot predisposition to that illness and medications that stop or even reverse the condition.
Using a highly inbred dog as the model should greatly help the identification process.
The human genome was published in draft form in February 2001 in a race between two rival teams of scientists. It was followed by the mouse (December 2002), rat (March 2004) and chimpanzee (August 2005).
Other organisms whose genetic code has been unraveled include a small earthworm-like animal called the nematode, the fruit fly and yeast. Like the mouse and rat, these are fundamental tools in lab research.
Copyright Â© 2005 Discovery Communications Inc.
Hsien Hsien Lei, PhD also discusses the Implications of the Dog Genome over at the Genetics and Health Blog