September 26, 2003.
By Earl Lane,
Washington - It turns out Fido may be more like his master than you may have imagined. Researchers have completed a rough draft of the genetic blueprint for the dog and have found an equivalent dog gene for 75 percent of the known human genes.
"It's quite fascinating to see how close our DNA sequence is to dogs," said Ewen Kirkness, lead author on a study published today in the journal Science. "It was quite an eye- opener." Kirkness said he has a new appreciation for his own dog, Emma, a mostly Labrador mongrel. "You look at your dog a little differently," he said.
Kirkness and his colleagues at The Institute for Genomic Research and The Center for the Advancement of Genomics, both in Rockville, Md., used a new technique to quickly sift through the genome, or DNA genetic blueprint, of a male standard poodle, the pet of genome researcher J. Craig Venter.
The dog genome consists of about 2.4 billion chemical building blocks, called base pairs, compared with about 2.9 billion base pairs in the human genome and 2.5 billion for the mouse. The research team found overlap between the human and dog DNA of about 650 million base pairs and identified a core set of common genes. Dogs share about 18,000 of some 24,000 clearly identified human genes.
Such information will be useful, scientists said, in understanding why mammals such as the dog, the human and the mouse - their obvious physical differences notwithstanding - seem to retain large blocks of similar DNA despite millions of years of divergent evolution from a common ancestor.
Moreover, the data should offer insights on the genetic origin of diseases dogs and humans have in common. "Both humans and dogs will benefit from us having the sequence data for the dog," said Elaine Ostrander, a canine genetics specialist at the Fred Hutchinson Cancer Research Center in Seattle. She said the diseases include cancer, heart disease, cataracts, deafness and retinitis pigmentosa, an eye disorder.
Ostrander said the new research shows valuable information can be extracted from a mammal's genome with a shortcut that is cheaper and quicker than full sequencing.
"This bodes well for doing more species" using the quicker genome analysis method, said William Murphy of the Laboratory of Genomic Diversity at the National Cancer Institute. But Murphy said researchers will continue to pursue more thorough sequence data on various mammal genomes as well, particularly those such as the dog that are more distant from humans on the evolutionary tree. A research team at the Whitehead Institute for Biomedical Research in Cambridge, Mass., is doing a more comprehensive sequencing of the dog genome.
According to Kirkness, there was a proliferation of mammals about 75 million to 100 million years ago, with four groups of placental mammals descending from a common ancestor. Humans and mice are thought to be in one of those lineages, dogs in another. Dogs diverged from the common ancestor more quickly than humans and mice. And yet the new research suggests the mouse, because it has nearly a twofold faster DNA mutation rate than dogs or humans, is now less genetically similar than the other two species.
Still, like the dog, the mouse shares many individual genes in common with humans, about 75 percent to 80 percent, according to Kirkness. The roughly 75 percent of shared genes are thought to be those which all three species shared with a common ancestor. Most of the other 25 percent likely arose since the species diverged, he said.
In examining the genomes of the dog, mouse and human, the researchers also found more than 370,000 small stretches of DNA in common, called conserved sequence blocks, whose function is unknown. Scientists suspect such segments are involved in regulation of genes.
The new research already is paying dividends for scientists looking for individual disease genes in dogs. "It has expedited the rate at which we can do our work enormously," Ostrander said. She, like Kirkness, has a dog. "I'm owned by a border collie named Tess," Ostrander said. "She is looking to me to see if all these things are going to meet her expectations."
All in the Animal Family
Dogs, and other creatures, too, have more in common with humans than one might think, at least genetically speaking.
Copyright © 2003, Newsday, Inc.
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