Science in the News Weekly
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Biologists Unveil HapMap, a Key to Genetic Variations Behind Disease
Geneticists completed a map of human genetic variation, the one-tenth of a percent of the human genome where genetic changes make one person distinct from another. Genes that contribute to diseases such as cancer, diabetes and hypertension lurk among those variations, and the new map provides an important tool for scientists attempting to ferret out the genetic markers of those diseases.Before the maps publication, biologists had to scour all 3 billion individual nucleotides to spot individual variations, called single nucleotide polymorphisms, or SNPs. The new map capitalizes on the revelation that SNPs can be spotted by looking for variation at the level of haplotypes, larger strings of DNA that are inherited together. That reduces to 1 million the number of places to search for genetic change.By making the search for genes tied to disease susceptibility more efficient, researchers hope to more quickly develop new tools for diagnoses and treatment. Teams have already begun screening the haplotypes of people with various diseases and comparing them to haplotypes taken from healthy people to spot the genetic differences that highlight susceptibility to both chronic and infectious diseases.The so-called HapMap was announced at the meeting of the American Society of Human Genetics and was published in the journal Nature. HapMap was created using genetic information taken from 269 individuals around the world, including people from Japan, Nigeria, China and Utah.Two More Genes Tied to Dyslexia, Opening Door for Early InterventionThe discovery that two more genes are tied to dyslexia opens the way for development of a genetic test that could identify children likely to encounter severe reading problems. Last year, scientists for the first time identified a gene that, when flawed, impedes the normal wiring of a childs brain before birth. Now, geneticists have linked two more genes to the disorder, they announced Friday at the same meeting of the American Society of Human Genetics.There are as many as 12 genes that are involved in moving neurons into place to develop the brains circuitry. With three of those genes now identified, researchers should soon come up with a simple cheek swab test that could be given to children who come from families with a history of the dyslexia. Children who carry the genetic risk for the disorder could then be placed in very early intervention reading programs.The new discoveries provide for the first time a link between genes, brain development and a complex behavioral syndrome, Albert Galaburda of Harvard Medical School told the New York Times. Galaburda, an expert on developmental disorders, was not involved with the new research.One of the genes just linked to dyslexia, called DCDC2, codes for a protein that acts in the brains of both dyslexics and fluent readers. But researchers found far less of it in the brains of people with dyslexia. The other gene, Robo1, helps create connections between the two hemispheres of the human brain. It is less active in the brains of dyslexics, resulting in fewer dendrites in the regions dedicated to reading.