skin colour

S

spuriousmonkey

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Science 16 December 2005:
Vol. 310. no. 5755, p. 1737


'Little is known about the specific genes that contribute to the variations in human skin color. An exciting clue has now emerged from an unlikely source, a tiny aquarium fish. Working with a mutant line of zebrafish called golden, whose stripes are paler than those in wild-type fish, Lamason et al. (p. 1782; see the cover and the news story by Balter) found that the altered pigmentation was caused by a mutation in the slc24A5 gene, which encodes a protein potentially involved in cation exchange. The gene is highly conserved in vertebrates, and expression of the human gene in the golden zebrafish restored wild-type pigmentation. European populations carry a slightly different version of the slc24A5 gene than do African and East Asian populations. A genetic polymorphism that changes one amino acid in the coding region of the gene correlates with skin pigmentation levels, which suggests that slc24A5 may contribute to skin color in humans.'

It seems that quite a minor genetic difference can result in differences in skin colour.
 
"Temperament: constitution of a substance, body, or organism with respect to the mixture or balance of its elements, qualities, or parts : Makeup b : Complexion


complexion: 1 : the combination of the hot, cold, moist, and dry qualities held in medieval physiology to determine the quality of a body
2 a : an individual complex of ways of thinking or feeling b : a complex of attitudes and inclinations
3 : the hue or appearance of the skin and especially of the face <a dark complexion>
4 : overall aspect or character "

It is interesting to see that Complexion is related to mental/emotional side of a person. Neurons are long lived cells so mautations can exist life long.

May not be of your interest but just read.
http://www.hpathy.com/homeopathyforums/forum_posts.asp?TID=3747&PN=1
 
spuriousmonkey said:
Science 16 December 2005:
Vol. 310. no. 5755, p. 1737


'Little is known about the specific genes that contribute to the variations in human skin color. An exciting clue has now emerged from an unlikely source, a tiny aquarium fish. Working with a mutant line of zebrafish called golden, whose stripes are paler than those in wild-type fish, Lamason et al. (p. 1782; see the cover and the news story by Balter) found that the altered pigmentation was caused by a mutation in the slc24A5 gene, which encodes a protein potentially involved in cation exchange. The gene is highly conserved in vertebrates, and expression of the human gene in the golden zebrafish restored wild-type pigmentation. European populations carry a slightly different version of the slc24A5 gene than do African and East Asian populations. A genetic polymorphism that changes one amino acid in the coding region of the gene correlates with skin pigmentation levels, which suggests that slc24A5 may contribute to skin color in humans.'

It seems that quite a minor genetic difference can result in differences in skin colour.
Click to expand...

yessss.
quite.

minor genetic differences also result in other variations between populations.
:eek:
 
que?
what part wasn't clearly stated?

aside from skin color.....
genetic differences are also responsible for other variations
between populations.
why doesn't this make sense?
if certain traits are condusive in an environment,
then those traits would be passed on to subsequent generations.
I'm confused as to whether you're really not clear as to what I meant,
or if you're bristling to the suggestion that there are population differences.
I know it's a bit of a taboo thing to suggest... us all being tabula rasa and all...
 
I mean then what was the point of your comment? I still don't get it. I think you are trying to insinuate something. Why not state it clearly.
 
Surely, genes are responsible for everything, from thin noses, to short stature, to skin pigmentation, to hair colour; it's just that they're still being discovered, so what's the big deal?
 
exactly...
what is the big deal indeed.


you made it sound as if genetic differences being responsible
for skin color was something new and extraordinary...
maybe you were just stating the obvious, I don't know.

My statement stands as is, I wasn't hinting at anything else.
:cool:
The sentence seemed pretty clear to me.
 
http://www.theage.com.au/realfooty/...ne-as-predictor/2005/06/21/1119321733381.html
heres a link for a "sports" gene;

http://news.bbc.co.uk/1/hi/sci/tech/850358.stm
and one showing IQ to be hereditary;

http://www.modern-psychiatry.com/genetics4.htm
specific genes associated with longevity...

is this what you wanted? specific links?




I can understand why the locating of various genes responsible for
specific features are noteworthy, I don't understand otoh why
the statement I made saying that other differences between populations
are the result of minor genetic differences as well was upsetting.
What exactly did you think I was trying to imply?
 
YOU were stating the obvious.
And I'm still interested exactly what riled ya up so much...
what exactly did you think I was trying to imply?
 
A one sentence summary of a summary is bound to sound obvious.

I do not think the news is here that a gene is responsible for a trait.

Can there be large phenotypic varation caused by slight differences in genotype? Obviously. I have even more obvious news for you. Large phenotypic variation can occur with exactly the SAME genotype.

So maybe that wasn't the news worthiness of the article.

conclusion - you shouldn't judge news by a one liner summary of an external source (me)
 
Who cares what causes skin color differences?

And, since we seem to be on the topic of "races", what genetic variation causes big, fat, ponderous lips? Or wide, flaring nostrils? Or the heavy, bony brow? Or the kinky, black hair?

As I said/implied, who cares why ...if they're different, look different, act different, talk different, then hate 'em and discriminate against 'em! It's the human way ...we've been doin' it since the dawn of man and things ain't likely to change soon. :)

Baron Max
 
doesn't melenin cause skin color?

on a side note
the japanese bio-engineered a green glow in the dark mouse.
 
spuriousmonkey said:
A one sentence summary of a summary is bound to sound obvious.

I do not think the news is here that a gene is responsible for a trait.

Can there be large phenotypic varation caused by slight differences in genotype? Obviously. I have even more obvious news for you. Large phenotypic variation can occur with exactly the SAME genotype.

So maybe that wasn't the news worthiness of the article.

conclusion - you shouldn't judge news by a one liner summary of an external source (me)
Click to expand...

"Can there be large phenotypic varation caused by slight differences in genotype? Obviously."

I think, I previously tried to discuss you on this aspect but...

Complexion is related the mental/sensation side. What can be passed from current genaration to next generation---may be the changes/mutations in our long lived cells?
 
...this gene can’t be said to be responsible for skin colour. The article says 'which suggests that slc24A5 may contribute to skin colour in humans'. Skin colour, like any of the phenotypes being talked about, are the result of a complex interaction of different genes (a confusion between gene p and gene d -see Lenny Moss’s book). I found it quite interesting and not obvious that ‘slc24A5 gene, which encodes a protein potentially involved in cation exchange’ would be involved in this network.

'It seems that quite a minor genetic difference can result in differences in skin colour.' well it at least results in lighter bandings on one type of fish, might have little to do with observable phenotypes in human skin colours. :)

weebee
 
What are long term/chronic disorders related to? I think, genetic predispositions, scarring/fibrosis or permanent damages to tissues, degenarations, mutations in cells with long life (neurons, Tcells..), cancer cells (Can you name some more). What out of these can pass to next generations and how than can effect complexion? I tried to relate complexion with mental side.
 
Since I am not sure the news section in Science is freely available i will post some quotes from the news article on the original article. Maybe this will clarify some matters:

People come in many different hues, from black to brown to white and shades in between. The chief determinant of skin color is the pigment melanin, which protects against ultraviolet rays and is found in cellular organelles called melanosomes. But the genetics behind this spectrum of skin colors have remained enigmatic. Now, on page 1782 of this week's issue of Science, an international team reports the identification of a zebrafish pigmentation gene and its human counterpart, which apparently accounts for a significant part of the difference between African and European skin tones. One variant of the gene seems to have undergone strong natural selection for lighter skin in Europeans.
Click to expand...

The new work is raising goose bumps among skin-color researchers. "Entirely original and groundbreaking," says molecular biologist Richard Sturm of the University of Queensland in Brisbane, Australia. Anthropologist Nina Jablonski of the California Academy of Sciences in San Francisco, California, notes that the paper "provides very strong support for positive selection" of light skin in Europeans. Researchers have not been sure whether European pale skin is the result of some selective advantage or due to a relaxation of selection for dark skin, after the ancestors of modern Europeans migrated out of Africa into less sunny climes.
Click to expand...

Yet the authors agree that the new gene, SLC24A5, is far from the whole story: Although at least 93% of Africans and East Asians share the same allele, East Asians are usually light skinned too. This means that variation in other genes, a handful of which have been previously identified, also affects skin color.
Click to expand...

and for our resident racists:
Barsh adds that the paper "indicates how the genetics of skin-color variation is quite different from, and should not be confused with, the concept of race." Rather, he says, "one of the most obvious characteristics that distinguishes among different humans is nothing more than a simple change in activity of a protein expressed in pigment cells." Jablonski agrees: "Skin color does not equal race, period."
Click to expand...

From the original article:
Variation of skin, eye, and hair color in Europeans, in whom a haplotype containing the derived Thr111 allele predominates, indicates that other genes contribute to pigmentation within this population. For example, variants in MC1R have been linked to red hair and very light skin [reviewed in (37)], whereas OCA2 or a gene closely linked to it is involved in eye color (7, 38). The lightening caused by the derived allele of SLC24A5 may be permissive for the effect of other genes on eye or hair color in Europeans.

Because Africans and East Asians share the ancestral Ala111 allele of rs1426654, this polymorphism cannot be responsible for the marked difference in skin pigmentation between these groups. Although we cannot rule out a contribution from other polymorphisms within this gene, the high heterozygosity in this region argues against a selective sweep in a population ancestral to East Asians. It will be interesting to determine whether the polymorphisms responsible for determining the lighter skin color of East Asians are unique to these populations or shared with Europeans.
Click to expand...
 
Barsh adds that the paper "indicates how the genetics of skin-color variation is quite different from, and should not be confused with, the concept of race." Rather, he says, "one of the most obvious characteristics that distinguishes among different humans is nothing more than a simple change in activity of a protein expressed in pigment cells." Jablonski agrees: "Skin color does not equal race, period." ”




this is true,
for instance, there are ethnic populations in India who's skin is much darker than
those of African descent, blacker than blacks, so to speak; though no one would mistake them for negro.
 
Skin color gene in humans and fish

New Science paper on allele which explains much of the difference in pigmentation between Europeans and Sub-Saharan Africans. Interestingly, Sub-Saharan Africans and East Asians both share the same ancestral allele, which means that the light pigmentation of East Asians is not caused by this gene. From an accompanying news story in the magazine:

People come in many different hues, from black to brown to white and shades in between. The chief determinant of skin color is the pigment melanin, which protects against ultraviolet rays and is found in cellular organelles called melanosomes. But the genetics behind this spectrum of skin colors have remained enigmatic. Now, on page 1782 of this week's issue of Science, an international team reports the identification of a zebrafish pigmentation gene and its human counterpart, which apparently accounts for a significant part of the difference between African and European skin tones. One variant of the gene seems to have undergone strong natural selection for lighter skin in Europeans.

...

The new work is raising goose bumps among skin-color researchers. "Entirely original and groundbreaking," says molecular biologist Richard Sturm of the University of Queensland in Brisbane, Australia. Anthropologist Nina Jablonski of the California Academy of Sciences in San Francisco, California, notes that the paper "provides very strong support for positive selection" of light skin in Europeans. Researchers have not been sure whether European pale skin is the result of some selective advantage or due to a relaxation of selection for dark skin, after the ancestors of modern Europeans migrated out of Africa into less sunny climes.

Yet the authors agree that the new gene, SLC24A5, is far from the whole story: Although at least 93% of Africans and East Asians share the same allele, East Asians are usually light skinned too. This means that variation in other genes, a handful of which have been previously identified, also affects skin color.



...

The team concludes that between 25% and 38% of the skin-color difference between Europeans and Africans can be attributed to SLC24A5 variants.
And from the actual paper paper:

The allele frequency for the Thr111 variant ranged from 98.7 to 100% among several European-American population samples, whereas the ancestral alanine allele (Ala111) had a frequency of 93 to 100% in African, Indigenous American, and East Asian population samples (fig. S6) (29, 30). The difference in allele frequencies between the European and African populations at rs1426654 ranks within the top 0.01% of SNP markers in the HapMap database (29), consistent with the possibility that this SNP has been a target of natural or sexual selection.
Science 16 December 2005:
Vol. 310. no. 5755, pp. 1782 - 1786

SLC24A5, a Putative Cation Exchanger, Affects Pigmentation in Zebrafish and Humans

Rebecca L. Lamason et al.

Lighter variations of pigmentation in humans are associated with diminished number, size, and density of melanosomes, the pigmented organelles of melanocytes. Here we show that zebrafish golden mutants share these melanosomal changes and that golden encodes a putative cation exchanger slc24a5 (nckx5) that localizes to an intracellular membrane, likely the melanosome or its precursor. The human ortholog is highly similar in sequence and functional in zebrafish. The evolutionarily conserved ancestral allele of a human coding polymorphism predominates in African and East Asian populations. In contrast, the variant allele is nearly fixed in European populations, is associated with a substantial reduction in regional heterozygosity, and correlates with lighter skin pigmentation in admixed populations, suggesting a key role for the SLC24A5 gene in human pigmentation.

http://dienekes.blogspot.com/2005/12/skin-color-gene-in-humans-and-fish.html
 
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