Monkey sheds light on humans
2007-04-13 07:23
Washington - Scientists have decoded the genome sequence of rhesus monkeys proving they share 93% of man's genetic make-up which may help research into chronic illnesses, a study said on Thursday.
The unveiling of the rhesus monkey genome pattern is the third primate DNA sequence to be completed by scientists after that of humans and chimpanzees.
"The rhesus macaque genome helps illuminate what makes humans different from other apes," said Richard Gibbs, director of the Baylor College of Medicine Human Genome Sequencing Centre in the study published in the US magazine Science.
"It allows us to learn what has been added or deleted in primate evolution from the rhesus macaque to the chimpanzee to the human.
"This sequence and its comparison to that of the human and chimpanzee enable us to look back at history at how these species evolved and diverged."
The human genome sequence was unveiled in 2001 after years of research and has already begun providing clues to the evolution of man, yielding valuable information for the treatment of such diseases as cancer and Aids.
"But researchers knew they would benefit by having other genomes for comparison," said Gibbs, who heads up an international team of 170 scientists also examining the DNA sequences of gorillas, gibbons and marmosets.
The decoding in 2005 of the genetic make-up of man's closest cousin, the chimpanzee, revealed that the two species share 99% of their genes.
Chimps diverged from humans some six million years ago, while rhesus monkeys are relatively ancient and separated from man's lineage some 25 million years ago, the study said.
Providing a powerful tool
"Before this paper, analyses of this kind had focused on human and chimp, and they're so close that it's not interesting," said Adam Siepel, one of the co-authors of the study.
"The macaque gives us the ability to more sensitively detect subtle natural selection pressure."
By comparing the rhesus monkey's genes which have evolved over a longer period of some 25 million years, scientists can learn more about why and how genetic modifications happened.
On average the genes in humans and chimps evolved more quickly than in other primates, while in general primates' genes evolved faster than rodents and dogs which split off even earlier from the evolutionary tree, the study said.
By comparing the rhesus monkey to other primates, researchers also found nearly 200 genes which could be key players in determining differences between them.
These genes included those responsible for hair formation, immune response, membrance proteins and sperm-egg fusion.
Researchers speculate in the study that humans may be less hairy than monkeys because of an ancient climate change or some shift in what was deemed to be desirable by potential mates.
The rhesus monkey is already widely used in medical research because of its physiological similarities to man, and has helped understanding on the rhesus factor in blood, as well as development of the polio vaccine.
The monkey's response to the immunodeficiency virus, which lept from apes to man, also provides vital clues in research into Aids, the study said.
"The sequencing of the rhesus macaque genome, combined with the availability of the chimp and human genomes, provide researchers with another powerful tool to advance our understanding of human biology in health and disease," said Francis Collins, director of the National Genome Research Institute.
"It has become clear that comparing our genome with the genomes of other organisms is crucial to identifying what makes the human genome unique."