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Politics : Formerly About Advanced Micro Devices -- Ignore unavailable to you. Want to Upgrade?

To: combjelly who wrote (266150)	12/27/2005 1:25:24 PM
From: tejek	Read Replies (1) \| Respond to of 1579676

I originally read this story in the Seattle Times. The phrase that I have highlighted and italicized was deleted in the Times Union [presumbly for PC reasons]. Regarding human genetics, one of the interesting things to me is the influence of the Mongols in Germany, Eastern Europe and Russia. Specifically, a number of Germans, Russians and Eastern Europeans I've met have the sloe eyed feature common to Asians. I met one Russian who had the whitest skin a human can have and the most blue eyes and yet his eyes were very sloe eyed........he looked almost other worldly. Its too bad so much social reaction depends on human genetics. I find the human diversity created by differences in DNA to be really interesting. *********************************************************** Gene mutation behind light skin** Scientists say skin color only part of what defines a race By Rick Weiss THE WASHINGTON POST Friday, December 16, 2005 WASHINGTON — Scientists said Thursday that they had discovered a tiny genetic mutation that largely explains the first appearance of white skin in humans tens of thousands of years ago, a finding that helps solve one of biology's most enduring mysteries and illuminates one of humanity's greatest sources of strife. The work suggests that the skin-whitening mutation occurred by chance in a single individual after the first human exodus from Africa, when all people were brown-skinned. That person's offspring apparently thrived as humans moved northward into what is now Europe, helping to give rise to the lightest of the world's races. The Penn State University researchers warned against interpreting the find as a discovery of "the race gene." Race is a vaguely defined biological, social and political concept, they say, and skin color is only part of what race is and isn't. In fact, several scientists said, the new work shows just how small a biological difference is reflected by skin color. The newly found mutation involves a change of just one letter of DNA code out of the 3.1 billion letters in the human genome — the complete instructions for making a human being. "It's a major finding in a very sensitive area," said Stephen Oppenheimer, an Oxford University expert in anthropological genetics who wasn't involved in the study being published today in the journal Science. "Almost all the differences used to differentiate populations from around the world really are skin deep." The work raises a raft of new questions — not least of which is why white skin caught on so thoroughly in northern climes once it arose. Some scientists suggest that lighter skin offered a strong survival advantage for people who migrated out of Africa by boosting their levels of bone-strengthening vitamin D; others have posited that its novelty and showiness simply made it more attractive to those seeking mates. Sun intensity is great enough in sunny equatorial regions that the vitamin can still be made in dark-skinned people. The work also reveals for the first time that Asians owe their relatively light skin to different mutations. That means that light skin arose independently at least twice in human evolution, in each case affecting populations with the facial and other traits that are commonly regarded as the hallmarks of Caucasian and Asian races. Several experts said they feared that such revelations might wrongly overshadow the prevailing finding of genetics over the past 10 years: that the number of DNA differences between races is tiny compared with the genetic diversity found within any single racial group. The discovery, described in today's issue of the journal Science, was an unexpected outgrowth of studies Keith Cheng and his colleagues were conducting on inch-long zebrafish. Having identified a gene that, when mutated, interferes with its ability to make its characteristic black stripes, the team scanned human DNA databases to see if a similar gene resides in people. To their surprise, they found virtually identical pigment-building genes in humans, chickens, dogs, cows and many others species. They got a bigger surprise when they looked in a new database comparing the genomes of four of the world's major racial groups. That showed that whites with Northern and Western European ancestry have a mutated version of the gene. Skin color is a reflection of the amount and distribution of the pigment melanin, which in humans protects against damaging ultraviolet rays but in other species is also used for camouflage or other purposes. The mutation that deprives zebrafish of their stripes blocks the creation of a protein whose job is to move charged atoms across cell membranes, an obscure process that is crucial to the accumulation of melanin inside cells. Humans of European descent, Cheng's team found, bear a slightly different mutation that hobbles the same protein with similar effect. The defect does not affect melanin deposition in other parts of the body, including the hair and eyes, whose tints are under the control of other genes. timesunion.com