g*********d
发帖数: 233 | 1 发表在基因图谱年会的一项跨文化研究指出，东方人的发丝比西方人粗50％的现象
和一段EDAR
基因有关.
SAN DIEGO, CALIFORNIA--Whether you have a poker-straight black mane
or frizzy blond locks, your hair depends on your ancestry. Now
researchers have come closer to figuring out just how hair traits are
passed down. According to a talk presented here last week at the annual
meeting of the American Society of Human Genetics, a single genetic
variant may explain why East Asians have thicker hair fibers than other
populations. The discovery is part of a wave of newly found genes that
determine what individuals look like.
Anthropologists have long noticed that populations across the world
differ in hair type, skin color, and facial features. Finding the genes
that explain these differences became easier in 2005, when researchers
unveiled the International HapMap Project, a catalog of human genetic
variation that helps scientists home in on genes more quickly
(ScienceNOW, 26 October 2005). Geneticists at the University of Tokyo
and several other institutions in Japan, Thailand, and Indonesia have
now used the HapMap to explore why Japanese and Chinese people have
thick hair: The cross-sectional area of East Asian hair fibers averages
about 30% larger than that of Africans and 50% larger than that of
Europeans.
The researchers started with 170 candidate genes known to be
involved in hair development based on mouse studies and rare inherited
human diseases. They then narrowed this list by looking at how these
genes varied in three HapMap populations--Yoruba from Nigeria,
Europeans, and Japanese and Chinese. A variant in a gene called EDAR was
present in 88% of the Japanese and Chinese but not at all in the two
other groups. To see how this gene affected hair thickness, the
researchers examined hair fiber dimensions and DNA from 186 individuals
from two ethnic groups in Southeast Asia who have a variety of hair
types. Hair fibers were thickest in people who have two copies of the
East Asian version of EDAR.
The EDAR gene codes for ectodysplasin A receptor, which is part of a
molecular pathway that signals hair precursor cells to begin forming a
follicle. The variant may have been selected for in East Asians either
because thicker hair was beneficial in the cold north Asian climate or
because it is linked to some other trait, such as tooth shape, that gave
East Asians an advantage, concluded presenter Akihiro Fujimoto of the
University of Tokyo.
The EDAR allele wouldnt be all that useful for figuring out what
someone looks like from their DNA because it doesnt determine whether
hair is straight or curly, and hair thickness also varies with sex and
age, says co-author Ryosuke Kimura of Tokai University School of
Medicine in Kanagawa, Japan. However, he says it could be used as a
marker for East Asian ancestry. Indeed, notes molecular anthropologist
Mark Shriver of Pennsylvania State University in State College, the EDAR
allele had already jumped out in the HapMap analysis as being distinctly
East Asian. "It was only a matter of time before somebody focused in on
what the phenotype was," he says.
And more genes for physical traits are coming. At the same session,
researchers from Iceland and the Netherlands described several newly
discovered genes that contribute to eye and hair color--and freckling--
in Europeans. The finding, published online last week in Nature
Genetics, and others like it could be useful for investigating crime, as
well as for genetic anthropology, notes co-author, CEO of deCODE
genetics in Iceland. For example, knowing the gene for red hair allowed
researchers to report last week that some Neandertals were redheads
(Science, 26 October). Using such traits for DNA forensics "is clearly
where we are headed," says Shriver.
http://www.uscnlife.cn/web/page/news1102.htm | a**v
发帖数: 406 | 2 I do not care the hair is thicker; I care the other thing | M*****n
发帖数: 16729 | |
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