Dog genome unveiled
Venter's poodle Shadow joins ranks
of the sequenced.
26 September 2003
JOHN
WHITFIELD
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| Shadow has 18,473
genes with human equivalents. |
| © C. Venter |
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Shadow is getting on a bit. At nine years old, his
black coat is turning grey, and his favourite pastime
is eating.
But this ordinary poodle is guaranteed a place in the
annals of science. The dog is the latest animal to have
its genome sequenced. Shadow belongs to Craig Venter,
the researcher whose privately funded project sequenced
the human genome using his own DNA.
Shadow's sequence will aid the quest to identify human
genes and to understand diseases such as cancer, epilepsy,
narcolepsy and obsessive-compulsive disorder. It should
also help to breed healthier dogs and track canine evolution.
The new sequence reveals that 18,473 dog genes have
human equivalents. This already surpasses the 18,311
known from the mouse sequence. The team also found genes
related to a dog's life: they have many more that are
linked to smell than we do.
The freely available sequence is less complete than
those of mouse and human. "We have a lot of fragments,"
says Ewen Kirkness of The Institute for Genomic Research
in Rockville, Maryland, who led the project. About 2
million fragments, in fact, covering 80% of Shadow's
genome.
A rough survey can still provide a lot of information,
says genome researcher William Murphy of the National
Cancer Institute in Frederick, Maryland. "Given the
relatively low coverage, the results are pretty good,"
he says. The quick-and-dirty technique could be extended
to other species that don't merit a full genome project.
Meanwhile, a US government-funded venture is working
on a detailed dog genome, from a boxer called Tasha.
This is expected to be completed late this year or early
next. Boxers are among the least genetically variable
breeds, and so likely to give reliable reference sequence.
Dogs have 2.4 billion DNA letters, compared with our
2.9 billion, and 39 pairs of chromosomes to our 23.
Different breeds are more than 99% identical.
Dog trials
"Most human diseases have canine counterparts, and
dogs are closer to humans in size, lifestyle and lifespan
than rodents," says dog geneticist Gregory Acland of
Cornell University in Ithaca, New York. He has already
used Shadow's sequence in his work on eye disease.
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Dogs are closer to humans
in size, lifestyle and lifespan than
rodents.
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Gregory Acland
Cornell University
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There are more than 350 known genetic dog diseases,
surpassing all animals save humans. About 10% of Irish
setters, for example, carry a gene for an immune disease.
DNA testing has allowed breeders to avoid mating carriers.
The genome will accelerate the search for such genes,
says Jeff Sampson, chief geneticist with the UK Kennel
Club.
Others are using genetics to work out relations between
dogs. "The genome might help to reveal how breeds have
developed over the centuries," says Sampson. Comparisons
of the tiny differences between breeds might explain
why collies are so good at herding, or what gives bloodhounds
their acute sense of smell.
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