You're More Like a Monkey Than You Think, Study of Gene Similarities Shows

Monkey DNA Resembles Humans', 25 Million Years Later

http://www.bloomberg.com/apps/news?pid=20601091&sid=aFLXRVDysFAA&refer=india

By Rob Waters

April 12 (Bloomberg) -- Rhesus monkeys and humans, primates who diverged from a common ancestor 25 million years ago, still carry 97.5 percent of the same genes, scientists said.

The finding, announced online today by the journal Science, could enable more effective use of the monkey to test drugs and vaccines for humans, and may help geneticists answer questions about how early humans split from our ancestors, shed body hair and grew bigger brains, researchers said.

Teams at three U.S. universities, using powerful computers and $22 million in government funds, mapped a complete genome for the rhesus macaque after extracting DNA from the liver of a female monkey from India. The macaque is the third primate, after humans and chimpanzees, to have its genome published.

``It's exciting partly because of what it can tell us about the biological basis of being human,'' said Francis Collins, one of the leaders in the earlier mapping of the human genome and director of the National Human Genome Research Institute, which helped fund the macaque work.

``Before, with just the chimp and human genomes, you could look at differences between them but you couldn't decide which are responsible for chimpness and which are responsible for humanness,'' Collins said in a phone interview yesterday. ``Now being able to compare all three, you can find areas where rhesus and chimp are the same, but the human is different.''

Chimps and humans split off from each other more recently, about 5 million years ago, and share a greater number of common genes than humans and rhesus macaques. A three-way comparison, or ``triangulation,'' as Collins called it, can allow researchers to identify genes that are the same in macaques and chimps and changed in the human genome.

200 Differences

Initial comparisons of the human, chimpanzee and monkey suggest that only about 200 of the 23,000 genes that each species has include evolutionary changes, said Richard Gibbs, the overall coordinator of the effort and director of the Human Genome Sequencing Center at Baylor College of Medicine.

``The grail here is to say what is it that makes us specifically human and why don't we grow up and become chimps or macaques,'' Gibbs said. ``We've long given up the idea that just a few genes cause all the difference but still expect that a fairly short number'' are the key drivers.

Many of these genes affect reproduction and the immune systems, Collins said.

``It does look as if the immune system and reproductive systems have gone through more rapid change in recent evolution,'' said Collins. ``That makes sense since evolution cares a lot about reproduction and since the immune system is constantly being asked to respond to new threats and if it doesn't evolve, a species could be wiped out.''

Color-Coding Genes

The process of creating the map made use of sophisticated techniques. The teams first loaded the monkey's genetic material into a machine that separated the DNA and dyed each of the four chemicals contained in DNA a different color. A laser scanned the color-coded DNA, emitting telltale glows of red, green, yellow and blue, converting the chemical code into digital information.

From there, the work was on computers. Each team, using slightly different approaches, created separate ``assemblies'' of genetic information, said Gibbs. They then compared the three and merged them into a single map, each encompassing about 98 percent of the macaque's chromosomes, genes and proteins.

One of the reasons the rhesus macaque was chosen as the next primate to have its genes mapped is because its abundance and similarity to humans has made it widely used in drug testing. Pharmaceutical companies are ``extremely interested'' in the rhesus macaque genome and have been steadily downloading the pieces of its genome that the teams have been placing on publicly accessible websites, Collins said.

Drug Testing

``For drug companies that have been assessing whether a particular drug is safe and effective the rhesus macaque has been a good model,'' Collins said.

By being able to see how particular genes and proteins differ between humans and macaques, drug companies can gain a better sense as to whether drugs that are safe in macaques will also be safe in humans, he said.

Geneticists, it seems, are not easily satisfied. To really understand which genes changed to drive human evolution, the genomes of other primates must also be mapped, Collins says.

Next Up: Gorillas

Scientific teams are already at work decoding the gorilla genome and Collins hopes that advances in technology will accelerate the speed at which the genes of other species can be mapped. Three new genome sequencing systems which use ``radically new ways of doing DNA sequencing'' are now being tested, Collins said.

``If they work well and generate high quality data -- and people are now kicking the tires -- then in three years we might have DNA sequences of as many as 20 primates,'' Collins said.

The science has moved at a speed far more rapid than evolution since Collins and J. Craig Venter began a spirited competition to decode the human genome more than a decade ago.

``Did I have any idea things could move this quickly?'' said Collins. ``No way! I couldn't have dreamed of that. This has been an absolute wild roller coaster of a ride.''

Edited 1 time(s). Last edit at 04/13/2007 01:50AM by regli.