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Biotech / Medical : AFFYMETRIX (AFFX) -- Ignore unavailable to you. Want to Upgrade?

To: Ronald Kronemann who wrote (856)	6/1/1999 10:50:00 PM
From: semi_infinite	Respond to of 1728

More uses for Gene Chip Tuesday June 1 3:46 PM ET Chimpanzees Offer Window In Time On Human Genes By Maggie Fox, Health and Science Correspondent WASHINGTON (Reuters) - Researchers Tuesday said they have used chimpanzee and gorilla genes to open a window in time for analyzing human genes -- especially for disease risk. The team, at the National Human Genome Research Institute (NHGRI) in Bethesda, Maryland, used advanced ''gene chip'' technology to look at the tiny differences among humans -- differences like those that determine whether a person has blue or brown eyes, or that determine blood type. Each of these differences, known as a single nucleotide polymorphism (SNP, pronounced ''snip'', for short), can shed light on who is at risk from what disease. ''What we were trying to do was to look at the history of genetic variation in humans,'' the NHGRI's Joseph Hacia said in a telephone interview. ''What we ended up doing was looking at this through a very long-term perspective by looking at it in chimps and gorillas, who are our closest relatives on the genetic tree.'' The idea is that the more of these SNPs that are similar in humans, chimps and gorillas, the more likely the variation would have been around since they all parted company on the evolutionary tree. ''That would be the missing link, so to speak,'' Hacia said. Population geneticist Andrew Clark of Pennsylvania State University said usually scientists expect the variation found most commonly in the population will be the oldest one. But the chimp comparison can point to those that are common but which are not old. Some of these could have popped up as a result of natural selection. Natural selection is the basis of evolution -- tiny changes that give an organism a slight survival advantage tend to be passed on. This, he said in an interview, can be used to help screen for which genes contain disease-causing mutations. ''We can predict something about the disease site,'' he said. Humans and chimpanzees shared a common ancestor 5 million to 6 million years ago, while gorillas and humans shared a common ancestor 8 million years ago. Chimpanzee DNA is 98.5 percent identical to human DNA while gorilla DNA is 97.9 percent identical. Comparing these differences can help point to just which changes are the oldest and which potentially are the most important to survival. Writing in the journal Nature Genetics, Hacia's team said they screened the DNA from 400 people around the world, and found 214 sites on the genes where there are slight changes, known as polymorphisms, that chimps and gorillas also have. ''Knowing the age of a polymorphism could be important for disease research,'' Hacia said. ''By identifying ancestral nucleotides, we can learn which variant appeared in the population more recently,'' Clark added in a commentary in the journal. ''We are in a better position to judge which SNPs might be important in judging the risk of disease.'' The NHGRI researchers have not looked at specific disease sites yet -- for example, the BRCA gene which, when certain variations are present, can make a woman more prone to breast cancer. ''They were randomly chosen throughout the genome,'' Hacia said. ''Most of it doesn't mean anything.'' The experiment does show that the gene chip technology can work to quickly process information about the genes. It involves laying genetic material on a small glass plate, and looking at the patterns it forms using florescent chemicals and a laser microscope. ''It's sort of like a supermarket scanner,'' Hacia said. Many theories in science are just waiting for the right technology to appear before they can be proven, he added. --------------------------------------------------------------------------------