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"Race" gene found! Film @ 11

Discussion in 'Topics in Healthcare' started by EvoDevo, Dec 19, 2005.

  1. EvoDevo

    EvoDevo Forging a Different Path
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    No, this isn't a joke. Discuss:

    Scientists Find A DNA Change That Accounts For White Skin

    By Rick Weiss
    Washington Post Staff Writer
    Friday, December 16, 2005; A01

    Scientists said yesterday that they have 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.

    Leaders of the study, at Penn State University, warned against interpreting the finding as a discovery of "the race gene." Race is a vaguely defined biological, social and political concept, they noted, and skin color is only part of what race is -- and is not.

    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 expert in anthropological genetics at Oxford University, who was not involved in the work. "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.

    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 today are commonly regarded as the hallmarks of Caucasian and Asian races.

    Several sociologists and others 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 range of genetic diversity found within any single racial group.

    Even study leader Keith Cheng said he was at first uncomfortable talking about the new work, fearing that the finding of such a clear genetic difference between people of African and European ancestries might reawaken discredited assertions of other purported inborn differences between races -- the most long-standing and inflammatory of those being intelligence.

    "I think human beings are extremely insecure and look to visual cues of sameness to feel better, and people will do bad things to people who look different," Cheng said.

    The discovery, described in today's issue of the journal Science, was an unexpected outgrowth of studies Cheng and his colleagues were conducting on inch-long zebra fish, which are popular research tools for geneticists and developmental biologists. 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, an indication of its biological value.

    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 zebra fish 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.

    A few genes have previously been associated with human pigment disorders -- most notably those that, when mutated, lead to albinism, an extreme form of pigment loss. But the newly found glitch is the first found to play a role in the formation of "normal" white skin. The Penn State team calculates that the gene, known as slc24a5, is responsible for about one-third of the pigment loss that made black skin white. A few other as-yet-unidentified mutated genes apparently account for the rest.

    Although precise dating is impossible, several scientists speculated on the basis of its spread and variation that the mutation arose between 20,000 and 50,000 years ago. That would be consistent with research showing that a wave of ancestral humans migrated northward and eastward out of Africa about 50,000 years ago.

    Unlike most mutations, this one quickly overwhelmed its ancestral version, at least in Europe, suggesting it had a real benefit. Many scientists suspect that benefit has to do with vitamin D, made in the body with the help of sunlight and critical to proper bone development.

    Sun intensity is great enough in equatorial regions that the vitamin can still be made in dark-skinned people despite the ultraviolet shielding effects of melanin. In the north, where sunlight is less intense and cold weather demands that more clothing be worn, melanin's ultraviolet shielding became a liability, the thinking goes.

    Today that solar requirement is largely irrelevant because many foods are supplemented with vitamin D.

    Some scientists said they suspect that white skin's rapid rise to genetic dominance may also be the product of "sexual selection," a phenomenon of evolutionary biology in which almost any new and showy trait in a healthy individual can become highly prized by those seeking mates, perhaps because it provides evidence of genetic innovativeness.

    Cheng and co-worker Victor A. Canfield said their discovery could have practical spinoffs. A gene so crucial to the buildup of melanin in the skin might be a good target for new drugs against melanoma, for example, a cancer of melanin cells in which slc24a5 works overtime.

    But they and others agreed that, for better or worse, the finding's most immediate impact may be an escalating debate about the meaning of race.

    Recent revelations that all people are more than 99.9 percent genetically identical has proved that race has almost no biological validity. Yet geneticists' claims that race is a phony construct have not rung true to many nonscientists -- and understandably so, said Vivian Ota Wang of the National Human Genome Research Institute in Bethesda.

    "You may tell people that race isn't real and doesn't matter, but they can't catch a cab," Ota Wang said. "So unless we take that into account it makes us sound crazy."
    © 2005 The Washington Post Company
     
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  3. odrade1

    odrade1 UASOM alum
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    Personally, I find cultural & value differences among populations to be much more interesting than external physiological differences. The exception to this is information about race that can affect how healthcare should be delivered. I hope that as more genetic differences between races (or even between sub-groups with particular physiological characteristics) are discovered, we will use this knowledge to help people (i.e., in diagnosis and the selection of appropriate therapies).

    This reminds me of a problem we have in general in this country: there is a great deal of interest in science (the public is absolutely crazy for studies relating to science and health discoveries), but extraordinarily poor training in science. The GP (general public) doesn't really understand much of how science is done, or how to interpret the information once they hear it. And (frustratingly) the GP is also pretty bad at listening to the interpretive advice from the experts doing the study. The conservative conclusions of the original researchers are usually lost in the wash, due to the excitement engendered by the original finding, and what it means to the layperson.

    Apart from the obvious fact that people, like cars, aren't really different if you change their color, people will also forget the fact that the manner in which your skin cells collect (or fail to collect) melanin is an absurdly unimportant fact about someone, as a person.

    An aside:
    Maybe now we can punish racial hate crime offenders by giving them gene therapy to add the properly functioning ion transporting protien to their skin cells. How funny to see the klansmen come back from jail a different color! They say that nothing teaches a man compassion and understanding like having to walk a mile in another's shoes....
     
  4. Shredder

    Shredder User
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    humans and chimpanzees are more than 99% genetically identical, but i dont think people will argue that the difference between humans and apes has no biological validity. 99.9% has to be taken in scope--.1% of 3 billion is a lot of bases. SNPs SNPs...

    censor as needed, i just couldnt let this PC statement go unchallenged. the newspaper threw these few clauses in at the last minute to avoid heat, but i see right through it

    racial differences go far beyond skin color. there are more differences between various parts of the earth than just the intensity of the sun
     
  5. tank you

    tank you 2K Member
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    just curious shredder, what qualities do u think should be taken into account when talking about race?

    nice avatar, very pc haha
     
  6. indo

    indo Feed me a stray cat
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    I think people are afraid to identify genetic differences between people of different races. To thrive in Africa and to thrive in Northern Europe require slightly different genetic configurations. However, calling a gene that codes for skin color the "race" gene is almost ******ed. That is an example of how the media will do anything for ratings.
     
  7. Shredder

    Shredder User
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    there are analogs between human races and animals. dogs, mice, horses. i mean comparing each species within itself, not among species. subspecies, you could say, or breeds. size, temperament, wits, coat, longevity, alcoholism, you name it. labs and pitbulls just arent the same. and no amount of training can change the pitbull, there are intrinsic differences. to tie it into healthcare, susceptibilities to disease differ as well. obvious examples are sickle cell anemia and tay sachs but i think it goes beyond that even, to subtleties. ive never heard of anything called a breed gene, i suspect it wont be identified.

    humans see themselves as separate from other evolutionary creations of mother nature. i guess its an ego thing. true scientific minds can see beyond. politicized science cannot. the truth should be independent from personal feelings. ill be straightforward, i think race is a very interesting subject with lots of implications for past present and future. i enjoy discussing it when things remain intellectual.

    secular Christmas is no good
     
  8. microbe hunter

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    Interesting, I would have thought that more than one gene would contribute to differences in skin color.

    The genetic variability between races is not as much as intra-race variability. Something like skin color would have to be controlled by genes. Any other diferences? Probably not.
     
  9. odrade1

    odrade1 UASOM alum
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    So that's the ONE trait that is controlled by genes? That's a little ridiculous. So pygmies aren't short due to any genetic differences between them and Swedes? How about eye color, bone density, resistance to certain diseases, susceptibility to certain diseases? There are tons of little differences between populations. Also, lots of other characteristics are partly to largely due to genetic expression. This includes "intangible" things like personality traits.

    People always try to dance around this issue. To a certain extent this concern is valid: people just love to make comparisons & anything that contributes to stereotypes tends to garner a lot of interest. Instead of being quietists about population & racial differences, we should study them with an eye to improving the human condition. The important thing to realize is that while differences may exist, and they may have a genetic component, these things don't affect the worth of the person as a human. Because of past (and present) racism, we need to discuss these topics with seriousness and caution. Why be a quietist about such findings, however? I am excited by the idea of genetically-informed medical treatments; racial studies fit in with this as well.

    I think you are correct about the more than one gene thing: Or rather, If I remember my freshman biology text properly, there are several sets (at least three pairs) of the allele that governs skin color. The color of the skin is affected by how much melanin the cells absorb & retain. The mutant copy of the allele codes for a defective ion tranporting protein, which affects the proper retention of melanin. The fewer wild type copies of the allele, the lighter your skin. Skin color is a polygenic character. It is also multifactorial, since exposure to sun interacts with allele expression to determine the actual skin color.
     
  10. Napoleon4000

    Napoleon4000 Senior Member
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    To the person who wrote the original comment. Please read the Science paper before making bold claims.

    Science. 2005 Dec 16;310(5755):1782-6.
    http://www.sciencemag.org/cgi/content/full/310/5755/1782

    In the article the authors say that skin pigmentation in humans is multigenetic. Please read your science carefully before making such bold statements or you will border more on pure speculation rather than science.
     
  11. Sainttpk

    Sainttpk Senior Member
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    I'd argue that culture and religion are the driving factors in regional differences. Not so called "race" such a silly idea.
     
  12. diosa428

    diosa428 SDN Angel
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    The OP posted an article written by a writer for the Washington Post. Those weren't his statements. Please read other's posts more carefully before posting obnoxious comments about them.
     

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