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The diversity of the eye colours of Europeans has long intrigued many. It is now claimed that there really are no specific genes for such--simply variations in SNIP arrangements, etc.
The study, which focused on twins, their siblings and parents, shows - conclusively - that there is no "gene" for eye colour.
Everyone has two copies of a SNP. So there are several possible combinations, some of which are more heavily associated with, for example, blue eyes, than with brown eyes.
In short, these combinations strongly influence the colour of a person's eyes, but they are not the final word.
Dr Richard Sturm and his colleagues found three SNPs near the start of the OCA2 gene that were linked to blue eye colour.
"The SNPs we've identified in themselves are not functionally causing the eye colour change, but they are linked very, very closely to something that is," Dr Sturm, from the University of Queensland, told BBC News.
"When OCA2 is knocked out, there is a loss of pigmentation. The position of these SNPs right at the start of the gene means it is possible we're looking at a change in the regulation of the gene in people with blue eye colour."
Functional change
So these SNPs, at the start of OCA2, probably regulate how much of the pigmentation protein is produced by the gene. People with brown eyes might have a lot of this protein, while people with blue eyes have less.
However, the single letter changes involved in green eyes may actually produce functional changes in the pigmentation protein.
The researchers found SNPs at another position in the OCA2 region - linked to green eyes - that resulted in changes to amino acids (the building blocks of a protein).
"To use an analogy, one of the changes is like switching the light on and off, while the other is like changing the light bulb from brown to green," said Dr Sturm.
Altogether, the single letter changes identified in the study accounted for 74% of total variation in eye colour, the researchers said.
The study was a collaboration between researchers at the Queensland Institute of Medical Research and the University of Queensland, both in Brisbane.
posted
And many people are unaware that even among black populations as extremely rare as it is, light colored eyes can and do occur.
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Interesting phenomenon though: North East Asians no matter how much dipigmented never seem to carry anything but the SNPS for jet black hair and dark eyes. Yet the Australian Aboriginese--very dark in pigmentation--are sometimes seen to carry the SNPS for hair blondism, but not blue eyes.
As some U.S. rapper might say: Mother Nature is a mutha.
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quote:Originally posted by lamin: Interesting phenomenon though: North East Asians no matter how much dipigmented never seem to carry anything but the SNPS for jet black hair and dark eyes. Yet the Australian Aboriginese--very dark in pigmentation--are sometimes seen to carry the SNPS for hair blondism, but not blue eyes.
As some U.S. rapper might say: Mother Nature is a mutha.
The matter only becomes perplexing when it is assumed that a polymorphism of a single gene causes variation in human phenotype pigmentation, and that a single gene controls pigmentation in skin, eyes and hair:
Again, from the aforemention link...
Where knowledge has improved over the past century has been in precisely how many genes are involved and their specific loci. As of 1998, five human pigmentation genes had been identified. Their symbols and genome loci are: “TYR” at 11q14-21, “TYRP1” at 9p23, “TYRP2” at 13q31-32, “P” at 15q11.2-12, and “MC1R” at 16q24.3 (Sturm, Box, and Ramsay 1998).
Subsequent work has identified five non-synonymous polymorphisms at the MC1R site (Rana and others 1999). Polymorphisms have been related to phenotype (Harding and others 2000). And gene-enzyme-protein reaction chains have been identified (Kanetsky and others 2002).
Much of the genetic mechanism remains to be unraveled but one conclusion is pertinent to this essay. Several independent genes must work in concert to produce the deepest complexion—the extreme of the darkness adaptation.
Many things can go wrong and, when they do, the result is a lighter complexion. For instance, deleterious mutations at the five loci above result in various forms of albinism, whether the patient’s heritage is dark or pale. In other words, there are many random ways “accidentally” to evolve a light complexion. **But no genetic defect can make the child of light-skinned parents come out dark.** [Nelson’s syndrome does this, but it is due to a pituitary tumor, not to a mutation, nor to genetic variability (Robins 1991, 125-26).] - Frank Sweet
While phenotypic pigmentation genes appear to have correspondence with one another, whatever the degree, this doesn't mean that eye pigmentation is necessarily directly linked to the polymorphisms in say, a gene at certain locus which has effect on the production of melanin in skin. As mentioned above, the interaction of many "independent" genes appear to be necessary for the production of dark skin, and it is much more easier for loss of dark skin to occur by these polymorphisms, because the product is 'recessiveness', or else 'deficiency'. Hence, the odds of recessive pigmentation genes resulting in dark color, is much, much higher than vice versa.
As noted before, even what we refer to as 'depigmented' in north Europeans, can be somewhat misleading, especially to the laymen who don't read into the implication, since even they exhibit some level of melanin in skin, although this cannot be produced to the levels seen in much darker populations. What little more these folks can possibly produce, results in reddish-burnt skin, called 'tanning'; that is it. The light skin here is a recessive trait, but nonetheless selected for. So it is no coincidence that these folks exhibit more recessive phenotype pigmentation traits than many others. "Blondism" in the case of the likes of Australian aborigines and Melanesians, I've come across a rationalization that the trait of ‘blond’ hair could be dominant one, unlike that seen in Europeans. Don’t know the validity of this explanation [indeed questionable, given that 'blondism' appears to be 'loss' of color or pigmentation], although the trait itself seems to be relatively more prevalent in the adolescent and females than adult males.
From the aforementioned discussion, recalling:
“Third, paleness and lactose tolerance are both neotenous adaptations that merely delay an existing developmental change until later in the organism’s life (until past its life-span, in these cases). Skin, like hair, normally darkens at puberty (Relethford, Lees, and Bayard 1985).”
And females, who have other neotenous features (associated with human sexual dimorphism) are slightly lighter-skinned on average than men (Rebato and others 1999). The point is that neotenous adaptations can be very fast indeed—as fast as one generation for some salamanders (Gould 1977, 319). [Otherwise important distinctions among neoteny, paedomorphosis, and postdisplacement are irrelevant to the point being made.]
An alternative explanation is that the extraordinary paleness of Europeans was due to sexual selection—it was more attractive to the opposite sex (Cavalli-Sforza, Menozzi, and Piazza 1994, 145). The problem with this speculation is that sexual selection normally results in a trait’s strong sexual dimorphism.
Incidentally, Cavalli-Sforza also advocates a Neolithic time frame for both the paleness and lactose tolerance adaptations, but *offers no mechanism for the former.* Ultimately, it all depends on evidence. The hypothesis presented here will be contradicted when someone finds evidence as early as Magdalenian cave art, that Paleolithic Europeans were as fair complexioned as Neolithic Europeans.” - Frank Sweet
It is possible that ‘blondism’ in tropical groups like Australian aborigines and Melanesians is “neotenous” in character, attributable to dietary habits or some yet-to-be specified response to the interactions of these groups with their natural environment. Studies specific to this trait would independently verify the underlying factors, but it is undoubtedly tied to workings of human pigmentation genes.
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As mentioned above, the interaction of many "independent" genes appear to be necessary for the production of dark skin, and it is much more easier for loss of dark skin to occur by these polymorphisms, because the product is 'recessiveness', or else 'deficiency'. Hence, the odds of recessive pigmentation genes resulting in dark color, is much, much higher than vice versa.
Correction: It would have been obvious to the very attentive individuals what I meant to say, still the need to excuse the erroneous language lest it [naturally] gave the wrong impression, which should have read:
"Hence, the odds against recessive pigmentation genes resulting dark color, is much, much higher than vice versa."
...meaning, virtually very slim to non-existent. The 'slim' chance presents itself only if the gene is 'temporarily' shut off, and then somehow activates at some point in time, i.e. delayed in its function of imparting pigment.
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quote:Originally posted by lamin: Interesting phenomenon though: North East Asians no matter how much dipigmented never seem to carry anything but the SNPS for jet black hair and dark eyes. Yet the Australian Aboriginese--very dark in pigmentation--are sometimes seen to carry the SNPS for hair blondism, but not blue eyes.
Although blue-eyes still occur among Australian aborigines and not associated at all with blonde hair and not having anything to do with European ancestry.
Posts: 26260 | From: Atlanta, Georgia, USA | Registered: Feb 2005
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quote:Originally posted by Djehuti: And many people are unaware that even among black populations as extremely rare as it is, light colored eyes can and do occur.
Of course. Albinism BEGAN in Africans...and ended in Europeans.
Posts: 3595 | From: Moved To Mars. Waiting with shotgun | Registered: Dec 2006
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quote:Originally posted by Djehuti: And many people are unaware that even among black populations as extremely rare as it is, light colored eyes can and do occur.
Of course. Albinism BEGAN in Africans...and ended in Europeans.
^ *No* it did'nt. Ofcourse your again talking non-sense.
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^ *YES* it did. Of course you're talking nonsense again.
Posts: 3595 | From: Moved To Mars. Waiting with shotgun | Registered: Dec 2006
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^ Many of the black African American photos Egmond has posted are false "whitened" images.
In the photos of the twins above, the one on the left with brown eyes is the lucky one, while the blue eyed one has the least best sight of the two and will develop serious eye problems later in life.
Posts: 3595 | From: Moved To Mars. Waiting with shotgun | Registered: Dec 2006
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quote:Originally posted by lamin: Interesting phenomenon though: North East Asians no matter how much dipigmented never seem to carry anything but the SNPS for jet black hair and dark eyes. Yet the Australian Aboriginese--very dark in pigmentation--are sometimes seen to carry the SNPS for hair blondism, but not blue eyes.
Although blue-eyes still occur among Australian aborigines and not associated at all with blonde hair and not having anything to do with European ancestry.
How is it possible that they are born with blue eyes and blonde hair anyway? What is the reason they evolved them for?
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Are there any South Africans with light brown eyes? I don't mean coloreds. But the pure tribes like the Xhosa, Zulu who both have a lot of Khoisan genes to account for their light skin. And I've seen some Khoisan children with golden brown hair as well.
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Glad someone beat me to it, I was going to post apic of Beyonce too.
quote:Originally posted by Ebony Allen: How is it possible that they are born with blue eyes and blonde hair anyway? What is the reason they evolved them for?
The funny thing is they split off from the ancestral population for East Asians. It appears to be random.
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ScienceDaily (Jan. 31, 2008) — New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today.
“Originally, we all had brown eyes”, said Professor Eiberg from the Department of Cellular and Molecular Medicine. “But a genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a “switch”, which literally “turned off” the ability to produce brown eyes”. The OCA2 gene codes for the so-called P protein, which is involved in the production of melanin, the pigment that gives colour to our hair, eyes and skin. The “switch”, which is located in the gene adjacent to OCA2 does not, however, turn off the gene entirely, but rather limits its action to reducing the production of melanin in the iris – effectively “diluting” brown eyes to blue. The switch’s effect on OCA2 is very specific therefore. If the OCA2 gene had been completely destroyed or turned off, human beings would be without melanin in their hair, eyes or skin colour – a condition known as albinism.
Limited genetic variation
Variation in the colour of the eyes from brown to green can all be explained by the amount of melanin in the iris, but blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes. “From this we can conclude that all blue-eyed individuals are linked to the same ancestor,” says Professor Eiberg. “They have all inherited the same switch at exactly the same spot in their DNA.” Brown-eyed individuals, by contrast, have considerable individual variation in the area of their DNA that controls melanin production.
Professor Eiberg and his team examined mitochondrial DNA and compared the eye colour of blue-eyed individuals in countries as diverse as Jordan, Denmark and Turkey. His findings are the latest in a decade of genetic research, which began in 1996, when Professor Eiberg first implicated the OCA2 gene as being responsible for eye colour.
Nature shuffles our genes
The mutation of brown eyes to blue represents neither a positive nor a negative mutation. It is one of several mutations such as hair colour, baldness, freckles and beauty spots, which neither increases nor reduces a human’s chance of survival. As Professor Eiberg says, “it simply shows that nature is constantly shuffling the human genome, creating a genetic cocktail of human chromosomes and trying out different changes as it does so.”
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ScienceDaily (Jan. 31, 2008) — New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today....
The “switch”, which is located in the gene adjacent to OCA2 does not, however, turn off the gene entirely, but rather limits its action to reducing the production of melanin in the iris – effectively “diluting” brown eyes to blue.
Limited genetic variation
Variation in the colour of the eyes from brown to green can all be explained by the amount of melanin in the iris, but blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes. “From this we can conclude that all blue-eyed individuals are linked to the same ancestor,” says Professor Eiberg. “They have all inherited the same switch at exactly the same spot in their DNA.” Brown-eyed individuals, by contrast, have considerable individual variation in the area of their DNA that controls melanin production.
Questions:
1)Where did this genetic mutation in a single common ancestor occur?
Are we to assume that the girl below, shares this same common ancestor with a pale-skin blue eyed person, as exemplified in the image below, i.e. that of some pale-skin person's eye?
If so, what are we told about the uniparental marker that is strongly suggestive of this individual ancestor?
Now of course, that the level of melanin in the eyes is the cause of this electromagnetic illusion of the eye, as noted in the earlier posts -- is understood, but when it is said that there is "limited" genetic variation...
2)then it has to be assumed that there are variations nonetheless, no?
3) Is not possible that more variations allow for the amount of melanin that impart the electromagnetic illusion of 'brownness' than that of "blue", and yet, imply that the latter need not necessarily be the product of a UEP?
Last but not least,
4)Was the sampling sufficiently comprehensive globally; and if so, are we told anything about the makeup of this comprehensive global sampling that had been undertaken?
Posts: 7516 | From: Somewhere on Earth | Registered: Jan 2008
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ScienceDaily (Jan. 31, 2008) — New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today....
The “switch”, which is located in the gene adjacent to OCA2 does not, however, turn off the gene entirely, but rather limits its action to reducing the production of melanin in the iris – effectively “diluting” brown eyes to blue.
Limited genetic variation
Variation in the colour of the eyes from brown to green can all be explained by the amount of melanin in the iris, but blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes. “From this we can conclude that all blue-eyed individuals are linked to the same ancestor,” says Professor Eiberg. “They have all inherited the same switch at exactly the same spot in their DNA.” Brown-eyed individuals, by contrast, have considerable individual variation in the area of their DNA that controls melanin production.
Questions:
1)Where did this genetic mutation in a single common ancestor occur?
Are we to assume that the girl below, shares this same common ancestor with a pale-skin blue eyed person, as exemplified in the image below, i.e. that of some pale-skin person's eye?
If so, what are we told about the uniparental marker that is strongly suggestive of this individual ancestor?
Now of course, that the level of melanin in the eyes is the cause of this electromagnetic illusion of the eye, as noted in the earlier posts -- is understood, but when it is said that there is "limited" genetic variation...
2)then it has to be assumed that there are variations nonetheless, no?
3) Is not possible that more variations allow for the amount of melanin that impart the electromagnetic illusion of 'brownness' than that of "blue", and yet, imply that the latter need not necessarily be the product of a UEP?
Last but not least,
4)Was the sampling sufficiently comprehensive globally; and if so, are we told anything about the makeup of this comprehensive global sampling that had been undertaken?
Of course, the mutation began in Africa and part of the Albinism gene. Blue eyes are a defect associated with minimal melanin production due to OCA1 & 2 Albinism.
As with skin, melanin is present in the eye to accomplish two main functions. One, to protect the eye from damage by free radicals. Two, to convert radiation to electrical impulse. The decrease in melanin adversely affects both of these primary functions. This is true with either African Albinos or Europeans.
You may utilize and sampling of any population having Albinism. Blue/green/hazel eyes along with minimal to no skin melanin are primary detection symptom in Albinism. I hope this answers your questions. Posts: 3595 | From: Moved To Mars. Waiting with shotgun | Registered: Dec 2006
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ScienceDaily (Jan. 31, 2008) — New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today....
The “switch”, which is located in the gene adjacent to OCA2 does not, however, turn off the gene entirely, but rather limits its action to reducing the production of melanin in the iris – effectively “diluting” brown eyes to blue.
Limited genetic variation
Variation in the colour of the eyes from brown to green can all be explained by the amount of melanin in the iris, but blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes. “From this we can conclude that all blue-eyed individuals are linked to the same ancestor,” says Professor Eiberg. “They have all inherited the same switch at exactly the same spot in their DNA.” Brown-eyed individuals, by contrast, have considerable individual variation in the area of their DNA that controls melanin production.
Questions:
1)Where did this genetic mutation in a single common ancestor occur?
Are we to assume that the girl below, shares this same common ancestor with a pale-skin blue eyed person, as exemplified in the image below, i.e. that of some pale-skin person's eye?
If so, what are we told about the uniparental marker that is strongly suggestive of this individual ancestor?
Now of course, that the level of melanin in the eyes is the cause of this electromagnetic illusion of the eye, as noted in the earlier posts -- is understood, but when it is said that there is "limited" genetic variation...
2)then it has to be assumed that there are variations nonetheless, no?
3) Is not possible that more variations allow for the amount of melanin that impart the electromagnetic illusion of 'brownness' than that of "blue", and yet, imply that the latter need not necessarily be the product of a UEP?
Last but not least,
4)Was the sampling sufficiently comprehensive globally; and if so, are we told anything about the makeup of this comprehensive global sampling that had been undertaken?
Well, we can take a clear example from when Europeans posit Neanderthal admixture in humans, when in fact they are speaking about themselves, since Neanderthal wasn't around the world for it even to be possible. Anyway, As we can it states in the article, I figure they tested the places where are blue eyes are most common.
quote: Professor Eiberg and his team examined mitochondrial DNA and compared the eye colour of blue-eyed individuals in countries as diverse as Jordan, Denmark and Turkey . His findings are the latest in a decade of genetic research, which began in 1996, when Professor Eiberg first implicated the OCA2 gene as being responsible for eye colour.
Through further investigation, I've found that scientists have identified three different changes in the OCA2 gene that leads to blue eyes. These three changes probably aren’t the whole story. But scientists do nail down OCA2 as the critical eye color gene that distinguishes brown eyes from blue. In terms of eye color, OCA2 comes in two versions—brown (B) and blue (b). The brown version works in the stroma, while the blue version does not. Since the blue version doesn’t work there, no melanin builds up. So these individuals end up having blue eyes.
I've also found this...
quote:David L. Duffy,* Grant W. Montgomery,* Wei Chen, Zhen Zhen Zhao, Lien Le, Michael R. James, Nicholas K. Hayward, Nicholas G. Martin, and Richard A. Sturm
We have previously shown that a quantitative-trait locus linked to the OCA2 region of 15q accounts for 74% of variation in human eye color. We conducted additional genotyping to clarify the role of the OCA2 locus in the inheritance of eye color and other pigmentary traits associated with skin-cancer risk in white populations. Fifty-eight synonymous and nonsynonymous exonic single-nucleotide polymorphisms (SNPs) and tagging SNPs were typed in a collection of 3,839 adolescent twins, their siblings, and their parents. The highest association for blue/nonblue eye color was found with three OCA2 SNPs: rs7495174 T/C, rs6497268 G/T, and rs11855019 T/C (P values of 1.02×10-61, 1.57×10-96, and 4.45×10-54, respectively) in intron 1. These three SNPs are in one major haplotype block, with TGT representing 78.4% of alleles. The TGT/TGT diplotype found in 62.2% of samples was the major genotype seen to modify eye color, with a frequency of 0.905 in blue or green compared with only 0.095 in brown eye color. This genotype was also at highest frequency in subjects with light brown hair and was more frequent in fair and medium skin types, consistent with the TGT haplotype acting as a recessive modifier of lighter pigmentary phenotypes. Homozygotes for rs11855019 C/C were predominantly without freckles and had lower mole counts. The minor population impact of the nonsynonymous coding-region polymorphisms Arg305Trp and Arg419Gln associated with nonblue eyes and the tight linkage of the major TGT haplotype within the intron 1 of OCA2 with blue eye color and lighter hair and skin tones suggest that differences within the 5′ proximal regulatory control region of the OCA2 gene alter expression or messenger RNA–transcript levels and may be responsible for these associations.
Through further analysis, I've found the actual study from the article I initially posted.....
The human eye color is a quantitative trait displaying multifactorial inheritance. Several studies have shown that the OCA2 locus is the major contributor to the human eye color variation. By linkage analysis of a large Danish family, we finemapped the blue eye color locus to a 166 Kbp region within the HERC2 gene. By association analyses, we identified two SNPs within this region that were perfectly associated with the blue and brown eye colors: rs12913832 and rs1129038. Of these, rs12913832 is located 21.152 bp upstream from the OCA2 promoter in a highly conserved sequence in intron 86 of HERC2. The brown eye color allele of rs12913832 is highly conserved throughout a number of species. As shown by a Luciferase assays in cell cultures, the element significantly reduces the activity of the OCA2 promoter and electrophoretic mobility shift assays demonstrate that the two alleles bind different subsets of nuclear extracts. One single haplotype, represented by six polymorphic SNPs covering half of the 3′ end of the HERC2 gene, was found in 155 blue-eyed individuals from Denmark, and in 5 and 2 blue-eyed individuals from Turkey and Jordan, respectively. Hence, our data suggest a common founder mutation in an OCA2 inhibiting regulatory element as the cause of blue eye color in humans. In addition, an LOD score of Z = 4.21 between hair color and D14S72 was obtained in the large family, indicating that RABGGTA is a candidate gene for hair color.
Material and methods
A three-generation Danish family (CFB#694) representing 28 informative meioses was used for linkage analysis and the blue eye color locus was finemapped. The family used in the linkage analysis, association and haplotype studies were of Danish origin and retrieved from the Copenhagen Family Bank, the families used in this study (families CFB#604-1505) (Eiberg et al. 1989). Only families with siblings, who had blue and brown eyes, respectively, were included in the study. The parents and siblings were classified as blue-eyed (Fig. 1a) or brown-eyed (Fig. 1c or d) individuals. Haplotypes were constructed from 100 Danish informative selected trios families, and most of these parents were also included in the association studies. These 100 triosis represented 45 families where at least one individual had brown eyes and 55 families where all individuals had blue eyes. Families where green and brown eye color spots segregate were not used. The haplotypes were deduced manually from the family study. Additional control material for DNA sequencing was collected from two large Danish families from the Copenhagen Family Bank. Five individuals from Turkey with blue eyes, black hair and light skin and two individual from Jordan with blue eyes, black hair and dark skin were included in the association analysis. Additionally, two persons with natal heterochromia were examined. The blue eye color phenotype was defined as a complete lack of brown pigmentation (Fig. 1a), an intermediate phenotype was defined as “blue eye with blown dots” (Fig. 1b), an intermediate brown eye color phenotype was defined as hazel with a broad peripupillary ring and was named the BEY1 phenotype (Fig. 1c), and a complete brown pigmented eye color was defined as the BEY2 phenotype (Fig. 1d).
All individuals in the study were interviewed by questionnaires and asked to determine their own eye color from the categories: brown, blue, gray and green, and whether brown spots or brown peripupillar rings were present.
Hair colors were categorized as red, black, brown and blond hair at the time when the persons were between 20 and 30 years of age. In family CFB#694, the eye color for all individuals was documented by photos and all key persons were re-examined. All individuals with green eye color or blue or gray eye color with brown spots not located close to the pupil were excluded from the linkage and association studies. Genomic DNA was extracted from the whole blood using standard phenol/chloroform procedures and the study adhered to the tenets of the declaration of Helsinki.
Indeed it does seem they only tested individuals from Jordan, Denmark and Turkey.
Posts: 6572 | From: N.Y.C....Capital of the World | Registered: Jun 2008
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quote: The decrease in melanin adversely affects both of these primary functions. This is true with either African Albinos or Europeans.
Not really, OCA2 isn’t just involved in eye color. When it is completely broken, we end up with something called P-gene related oculocutaneous albinism. This is a form of albinism more common in Africans than in Europeans.
So to have blue eyes without albinism, OCA2 has to work everywhere except the stroma. Read my above post.
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^ Yes, you can have blue/Green/Hazel eyes without having FULL albinism. Still it is a major trait associated with full (OCA1) or partial (OCA2) Albinism.
Blue/Green eyes don't see as well, or last as long as normal fully melaninated eyes. The brown eyed twin drew the long straw for eyes, although he likely inherited some other symptom of OCA2 Albinism.
Posts: 3595 | From: Moved To Mars. Waiting with shotgun | Registered: Dec 2006
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^^^Yes lighter eyed individuals tend to be visually impaired a lot of the times. But what do you say about the millions upon millions of brown eyed individuals who are visually impaired and also need glasses?
Btw, again, only 5 individuals out of every 100,000 in Europe are albinos.
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^ What is there to say. Eyes can degrade over time. Genetics and environment determine what level of degradation they will see over time. Brown eyes degrade. Blue eyes are defective. There is a difference.
5/100000 are estimated to have OCA1 A much larger percentage are estimated to be afflicted with OCA2. To get a picture of how much larger. Just count the number of people with blue/green eyes and low skin melanin content. It shouldn't be as hard as counting the stars in the sky.
Posts: 3595 | From: Moved To Mars. Waiting with shotgun | Registered: Dec 2006
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quote: ^ What is there to say. Eyes can degrade over time. Genetics and environment determine what level of degradation they will see over time. Brown eyes degrade. Blue eyes are defective. There is a difference.
Whats the difference in the genes? What gene causes brown eyes and what causes blue eyes?
quote: 5/100000 are estimated to have OCA1 A much larger percentage are estimated to be afflicted with OCA2. To get a picture of how much larger. Just count the number of people with blue/green eyes and low skin melanin content. It shouldn't be as hard as counting the stars in the sky.
Not quite, as anthropologist Nina Jablonski tells us in her response, that the majority of "whites" DON'T have the mutations, just like the majority of humans worldwide don't have the mutations for OCA2. The medical article also explains what causes albinism and mentions the 10 types of the most common form of the condition, known as "oculocutaneous albinism," which affects the eyes, hair, and skin. All the while mentioning only 5 out of 100,000 have it.
quote: Nina Jablonski: ***Not all genes*** that cause clinically significant forms of hypopigmentation ***are members of the TYRP family***. The most common form of albinism worldwide, ***tyrosinase-positive oculocutaneous albinism***, is most often caused by mutations in a gene encoding a structural protein ***whose function remains poorly understood***. As this was the second albinism gene to be identified, the locus was designated OCA2. The OCA2 locus maps to chromosome 15q11.2–12,(51) and the gene is the human homologue, P, of the mouse pink-eyed dilution locus, p. The vast majority of 'whites' ***DON'T HAVE*** any of those mutations that cause albinism just like the ***majority of all human populations!***
Albinism is an inherited condition present at birth, characterized by a lack of pigment that normally gives color to the skin, hair, and eyes. Many types of albinism exist, all of which involve lack of pigment in varying degrees. The condition, which is found in all races, may be accompanied by eye problems and may lead to skin cancer later in life.
Description
Albinism is a **rare disorder** found in fewer than **five people per 100,000 in the United States and Europe**. Other parts of the world have a much higher rate; for example, albinism is found in about **20 out of every 100,000 people in southern Nigeria**.
There are 10 types of the most common form of the condition, known as "oculocutaneous albinism," which affects the eyes, hair, and skin. In its most severe form, hair and skin remain pure white throughout life. People with a less severe form are born with white hair and skin, which turn slightly darker as they age. Everyone with oculocutaneous albinism experiences abnormal flickering eye movements (nystagmus) and sensitivity to bright light. There may be other eye problems as well, including poor vision and crossed or "lazy" eyes (strabismus).
The second most common type of the condition is known as "ocular" albinism, in which only the eyes lack color; skin and hair are normal. There are five forms of ocular albinism; some types cause more problems--especially eye problems--than others.Posts: 6572 | From: N.Y.C....Capital of the World | Registered: Jun 2008
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posted
anthropologist Nina Jablonski cannot possibly know if MOST whites don't carry the Albinism gene since;
1) She is no Medical doctor
2) All medical doctors clearly state there is presently, no method on testing or determining if ALL or any large majority of any group of people carry the trait. The means of testing large populations does not yet exist. You cannot detect Albinism from random or population sampling. Therefore Ms. Nina is talking out of her Albino....
3) Albinism incident is highest in Ashkenazi Jews.
In the 1970's, a type of albinism associated with relatively normal skin and hair pigment was described in families that contained affected females and males. This appeared to be a type of ocular albinism that was caused by a gene on an autosome chromosome (non-sex chromosome) rather than on the X chromosome; hence, the name of autosomal recessive ocular albinism. We now know that this was incorrect and these families are actually part of the spectrum found in OCA1 and OCA2 . At this time, there is no evidence for a true AROA type of albinism, and this term should not be used.
How can you determine the type of albinism present?
It is usually possible to determine the type of albinism present with a careful history of pigment development and an examination of the skin, hair and eyes. The only type of albinism that has white hair at birth is OCA1. Individuals with other types of OCA will have some hair pigment at birth, although it may be very slight in amount. It can be difficult to tell if the hair is completely white or very lightly pigmented in a very young child, and changes in pigment over time will usually help clarify the OCA type present. In OCA1, The skin is white and does not tan on sun exposure. Iris color is blue to gray or lighted pigmented (light blue/green/gray/brown), and the degree of iris translucency correlates with the amount of pigment present. Some individuals who were previously thought to have autosomal recessive ocular albinism have now been shown to have OCA2.
The most accurate test for determining the specific type of albinism is a gene test. A small sample of blood is obtained from the affected individual and the parents as a source of DNA, the chemical that carries the 'genetic code' of each gene. By a complex process, a genetic laboratory can "sequence" the code of the DNA, to identify the changes (mutations) in the gene that cause albinism in the family. The test is useful only for families that contain individuals with albinism, and cannot be performed practically as a screening test for the general population.
None of the tests available are capable of detecting all of the mutations of the genes that cause albinism, and responsible mutations cannot be detected in a small number of individuals and families with albinism.
Richard A. King, M.D., Ph.D., Professor of Medicine and in the Institute of Human Genetics at the University of Minnesota, has conducted research on albinism for more than fifteen years, and coordinates the International Albinism Center.
C. Gail Summers, M.D., Associate Professor of Ophthalmology at the University of Minnesota, is involved in research on vision and albinism, and is co-director of the International Albinism Center.
James W. Haefemeyer, M.D., M.S., is a family practice physician in Minneapolis, Minnesota, who has albinism and is a NOAH Scientific Advisor.
posted
Ok let's see you know more than Nina Jablonski, a scholar with emphasis on human skin pigmentation??
:
EDUCATION:
* 1975 A.B., Bryn Mawr College (Biology) * 1978 Ph.C., University of Washington (Anthropology) * 1981 Ph.D., University of Washington (Anthropology)
RESEARCH ACTIVITIES AND INTERESTS:
*
Primate evolution, with emphasis on the evolution of primate lineages in relation to environmental change: Concentration on the illumination of the history of adaptation, and the relationship between environmental change and the evolution of life histories and diet in Old World primate lineages, especially tarsiers, monkeys, apes, and humans. Long-term interest in the evolution and biogeography of Old World monkeys. *
Evolution of human skin and skin coloration: Study of the origin and evolution of a functionally naked and pigmented integument in humans, drawing upon anatomical, physiological, paleontological, epidemiological, and environmental data *
Evolution of hominid bipedalism: Concentration on the identification of the behaviors which triggered the initial transition to bipedal posture and locomotion in the human lineage, with particular reference to the role of bipedal displays and the importance of physical stature * Mammalian paleoecology in the late Tertiary and Quaternary: Examination of the history of mammalian herbivores in relation to changes in local and global environments, and the differential evolution of brains, jaws, teeth, guts, and hooves in post-Miocene environments.
This is what she has to say on the matter of skin color.
quote:Nina Jablonski: There is no doubt that visual impressions of body form and color are important in the interactions within and between human communities. Remarkably, it is the levels of just one chemically inert and stable visual pigment known as melanin that is responsible for producing all shades of humankind. Major human genes involved in its formation have been identified largely using a comparative genomics approach and through the molecular analysis of the pigmentary process that occurs within the melanocyte. Three classes of genes have been examined for their contribution to normal human color variation through the production of hypopigmented phenotypes or by genetic association with skin type and hair color. The MSH cell surface receptor and the melanosomal P-protein are the two most obvious candidate genes influencing variation in pigmentation phenotype, and may do so by regulating the levels and activities of the melanogenic enzymes tyrosinase, TRP-1 and TRP-2.
..There are easily recognized differences in melanosome qualities of ethnic groups, as shown in ultrastructural studies of the skin.(15) Although the number of melanocytes is essentially constant, the number, size, and the manner in which the melanosomes are distributed within the keratinocytes vary. In general, more deeply pigmented skin contains numerous single large melanosomal particles that are ellipsoidal and intensely melanotic. Lighter pigmentation is associated with smaller and less dense melanosomes that are clustered in membrane bound groups. Melanosomes in black African skin are .0.8 μm, with Asian and Caucasian melanosomes averaging ,0.8 μm,(16) but there is variation in melanosome size within these groups. These distinct patterns of melanosome type and distribution are present at birth and are not determined by sun exposure.(17) It is possible that the formation of either single or aggregated melanosomes depends more on melanosome size, which may be influenced by nongenetic factors,(16) as well as genetic factors.
..The most dramatic example of gene action in pigmentation is seen in the complete loss of color resulting from the inability to form melanin. Albinism has been recorded in almost every species and the way in which the genes responsible for hypopigmented states have been identified demonstrates the power that a comparative molecular genetic approach has given to the study of pigmentation in humans...
The chromosomal locations of the loci for the three human TYRP genes have been determined, and searches have been conducted for functional polymorphisms that could explain natural variation in pigmentation phenotypes as well as several hypopigmented states. The TYR gene on chromosome 11q14–21 is encoded in five exons spanning more than 50–65 kb.(36,37) Many alleles responsible for OCA1 albinism have been identified,(38) but ethnic differences in the tyrosinase protein are rare, with only two apparently nonpathogenic amino acid substitutions reported. The Y192S(39) and R402Q variant substitutions are found in all populations except in Asian.
As TYRP1 is the third albinism locus to be identified, phenotypes caused by mutations in this gene are referred to as OCA3. Although the OCA3 newborn expressed normal amounts of tyrosinase that was catalytically active in cell lysates, tyrosinase activity was reduced by 70% when assayed in melanocytes cultured from the patient...
Not all genes that cause clinically significant forms of hypopigmentation are members of the TYRP family. The most common form of albinism worldwide, tyrosinase-positive oculocutaneous albinism, is most often caused by mutations in a gene encoding a structural protein whose function remains poorly understood. As this was the second albinism gene to be identified, the locus was designated OCA2. The OCA2 locus maps to chromosome 15q11.2–12,(51) and the gene is the human homologue, P, of the mouse pink-eyed dilution locus, p.
The vast majority of 'whites' DON'T HAVE any of those mutations that cause albinism just like the majority of all human populations!
The wide variety of pigment phenotypes seen in human populations prompts the question of whether there is likely to have been selection for skin color. Most of the Earth is populated with more darkly pigmented peoples, with a striking northern European localization of more lightly pigmented peoples.(84) One might argue in favor of selection for darkerskinned individuals who are better protected from the harmful effects of ultraviolet (UV) irradiation, but perhaps this was the ancestral state. A more likely scenario is that mutations that arose for lighter skin color have been selected for in individuals with poor dietary vitamin D intake and little exposure to the sun. Natural selection, although a possible driving force through latitudinal variation in sunlight, may not readily apply to humankind, which can so easily alter its environment and behavior, and where other factors are more important in choosing partners.
Posts: 6572 | From: N.Y.C....Capital of the World | Registered: Jun 2008
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quote:Originally posted by Knowledgeiskey718: Ok let's see you know more than Nina Jablonski, a scholar with emphasis on human skin pigmentation?? :
EDUCATION:
* 1975 A.B., Bryn Mawr College (Biology) * 1978 Ph.C., University of Washington (Anthropology) * 1981 Ph.D., University of Washington (Anthropology)
RESEARCH ACTIVITIES AND INTERESTS:
*
Primate evolution, with emphasis on the evolution of primate lineages in relation to environmental change: Concentration on the illumination of the history of adaptation, and the relationship between environmental change and the evolution of life histories and diet in Old World primate lineages, especially tarsiers, monkeys, apes, and humans. Long-term interest in the evolution and biogeography of Old World monkeys. *
Evolution of human skin and skin coloration: Study of the origin and evolution of a functionally naked and pigmented integument in humans, drawing upon anatomical, physiological, paleontological, epidemiological, and environmental data *
Evolution of hominid bipedalism: Concentration on the identification of the behaviors which triggered the initial transition to bipedal posture and locomotion in the human lineage, with particular reference to the role of bipedal displays and the importance of physical stature * Mammalian paleoecology in the late Tertiary and Quaternary: Examination of the history of mammalian herbivores in relation to changes in local and global environments, and the differential evolution of brains, jaws, teeth, guts, and hooves in post-Miocene environments.
This is what she has to say on the matter of skin color.
quote:Nina Jablonski: There is no doubt that visual impressions of body form and color are important in the interactions within and between human communities. Remarkably, it is the levels of just one chemically inert and stable visual pigment known as melanin that is responsible for producing all shades of humankind. Major human genes involved in its formation have been identified largely using a comparative genomics approach and through the molecular analysis of the pigmentary process that occurs within the melanocyte. Three classes of genes have been examined for their contribution to normal human color variation through the production of hypopigmented phenotypes or by genetic association with skin type and hair color. The MSH cell surface receptor and the melanosomal P-protein are the two most obvious candidate genes influencing variation in pigmentation phenotype, and may do so by regulating the levels and activities of the melanogenic enzymes tyrosinase, TRP-1 and TRP-2.
..There are easily recognized differences in melanosome qualities of ethnic groups, as shown in ultrastructural studies of the skin.(15) Although the number of melanocytes is essentially constant, the number, size, and the manner in which the melanosomes are distributed within the keratinocytes vary. In general, more deeply pigmented skin contains numerous single large melanosomal particles that are ellipsoidal and intensely melanotic. Lighter pigmentation is associated with smaller and less dense melanosomes that are clustered in membrane bound groups. Melanosomes in black African skin are .0.8 μm, with Asian and Caucasian melanosomes averaging ,0.8 μm,(16) but there is variation in melanosome size within these groups. These distinct patterns of melanosome type and distribution are present at birth and are not determined by sun exposure.(17) It is possible that the formation of either single or aggregated melanosomes depends more on melanosome size, which may be influenced by nongenetic factors,(16) as well as genetic factors.
..The most dramatic example of gene action in pigmentation is seen in the complete loss of color resulting from the inability to form melanin. Albinism has been recorded in almost every species and the way in which the genes responsible for hypopigmented states have been identified demonstrates the power that a comparative molecular genetic approach has given to the study of pigmentation in humans...
The chromosomal locations of the loci for the three human TYRP genes have been determined, and searches have been conducted for functional polymorphisms that could explain natural variation in pigmentation phenotypes as well as several hypopigmented states. The TYR gene on chromosome 11q14–21 is encoded in five exons spanning more than 50–65 kb.(36,37) Many alleles responsible for OCA1 albinism have been identified,(38) but ethnic differences in the tyrosinase protein are rare, with only two apparently nonpathogenic amino acid substitutions reported. The Y192S(39) and R402Q variant substitutions are found in all populations except in Asian.
As TYRP1 is the third albinism locus to be identified, phenotypes caused by mutations in this gene are referred to as OCA3. Although the OCA3 newborn expressed normal amounts of tyrosinase that was catalytically active in cell lysates, tyrosinase activity was reduced by 70% when assayed in melanocytes cultured from the patient...
Not all genes that cause clinically significant forms of hypopigmentation are members of the TYRP family. The most common form of albinism worldwide, tyrosinase-positive oculocutaneous albinism, is most often caused by mutations in a gene encoding a structural protein whose function remains poorly understood. As this was the second albinism gene to be identified, the locus was designated OCA2. The OCA2 locus maps to chromosome 15q11.2–12,(51) and the gene is the human homologue, P, of the mouse pink-eyed dilution locus, p.
The vast majority of 'whites' DON'T HAVE any of those mutations that cause albinism just like the majority of all human populations!
The wide variety of pigment phenotypes seen in human populations prompts the question of whether there is likely to have been selection for skin color. Most of the Earth is populated with more darkly pigmented peoples, with a striking northern European localization of more lightly pigmented peoples.(84) One might argue in favor of selection for darkerskinned individuals who are better protected from the harmful effects of ultraviolet (UV) irradiation, but perhaps this was the ancestral state. A more likely scenario is that mutations that arose for lighter skin color have been selected for in individuals with poor dietary vitamin D intake and little exposure to the sun. Natural selection, although a possible driving force through latitudinal variation in sunlight, may not readily apply to humankind, which can so easily alter its environment and behavior, and where other factors are more important in choosing partners.
LOL, Don't be emotional.
It's not me, but these guys who know more about Albinism than Mz. Jablonski.
They are the authors of the VAST Center For Albinism detection and practical treatment focused medical studies. Who would I approach for Albinism information, a medical doctor or an Anthropologist? Hmmm..tough choice, but I think I'll take the research of the former. If the subject has been dead for around 6,000 years I'd like to hear from the latter, but so far, we have seen little of this research from her. Does she have detailed Anthropology evidence from forensics from this time frame? I'd be extremely interested because so far, I have seen hardly any information on ancient melanin or Albinism evidence from these researchers.
Richard A. King, M.D., Ph.D., Professor of Medicine and in the Institute of Human Genetics at the University of Minnesota, has conducted research on albinism for more than fifteen years, and coordinates the International Albinism Center.
C. Gail Summers, M.D., Associate Professor of Ophthalmology at the University of Minnesota, is involved in research on vision and albinism, and is co-director of the International Albinism Center.
James W. Haefemeyer, M.D., M.S., is a family practice physician in Minneapolis, Minnesota, who has albinism and is a NOAH Scientific Advisor.
I would however, be extremely interested in viewing some of Ms. Jablonski's European sampling data. Not the fluff you've posted above, but the actual sampling and case parameters used to justify her opinion.
Also, according to The Mayo Clinic. Detailed visual inspection is still the primary detection method for Albinism;
Tests and diagnosis
A complete diagnostic workup will include a physical examination, a description of changes in pigmentation, a pigment history and a thorough examination of the eyes.
A pigment history includes a comparison of your child's pigmentation to that of other family members to determine if your child's is lighter. Your doctor may also ask you about any changes you may have observed in your child's hair, skin or eye color.
A medical doctor specializing in vision and eye disorders (ophthalmologist) will conduct your child's eye exam. The exam will include an assessment of potential nystagmus, strabismus and photophobia. He or she will also use a device to visually inspect the retina and determine if there are signs of abnormal development. A test called an electroretinogram, which measures brain waves produced when light is shined in the eye, can indicate the presence of misrouted optical nerves.
(As you can see, those afflicted with Albinism have mis-wiring of the optic nerves to the brain. This mis-wiring is directly connected to the insufficient levels of melanin present during the first months of fetal development. It is also directly tied to the light color of the eyes following birth which reflects low levels of melanin during brain formation. This is not the same as skin melanin, but neuromelanin. So, in a person with dark skin and blue eyes, they are able to manufacture sufficient melanin level for eumalanin production, but lower levels of neuromelanin, with is needed to form the brain, Brain, stem, and eyes/ears. Look carefully at the above figure. It clearly shows not only a difference in wiring of the optic nerves, but also a subtle difference in the formation of the brain itself.)
If your child has albinism, he or she will almost certainly have the whole spectrum of functional eye problems. If he or she has only one of the eye impairments, such as nystagmus, another condition may be the cause. Disorders other than albinism may affect skin pigmentation, but these wouldn't cause the visual problems associated with albinism.
As you notice in both twins, the twin on the left has a dark pupil/Iris coloring with a slight difference of melanin between the two, while the twin on the right has a darker pupil coloring with much lighter iris coloring. This (right twin) is one symptom of Albinism as show below, bearing in mind the figure below is not presented in color. The lighter Iris allows stray light to penetrate the eye, leading to photophobia, the reason the woman in your previous article was squinting so badly while facing the sun.
Also bear in mind, Ms. Jablonski only addresses melanin in skin color and does not provide any data on early levels of neuromelanins which are independently responsible for brain and eye formation which are as much a key to Albinism as Melanocytes are to skin color.
Posts: 3595 | From: Moved To Mars. Waiting with shotgun | Registered: Dec 2006
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ScienceDaily (Jan. 31, 2008) — New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today....
The “switch”, which is located in the gene adjacent to OCA2 does not, however, turn off the gene entirely, but rather limits its action to reducing the production of melanin in the iris – effectively “diluting” brown eyes to blue.
Limited genetic variation
Variation in the colour of the eyes from brown to green can all be explained by the amount of melanin in the iris, but blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes. “From this we can conclude that all blue-eyed individuals are linked to the same ancestor,” says Professor Eiberg. “They have all inherited the same switch at exactly the same spot in their DNA.” Brown-eyed individuals, by contrast, have considerable individual variation in the area of their DNA that controls melanin production.
Questions:
1)Where did this genetic mutation in a single common ancestor occur?
Are we to assume that the girl below, shares this same common ancestor with a pale-skin blue eyed person, as exemplified in the image below, i.e. that of some pale-skin person's eye?
If so, what are we told about the uniparental marker that is strongly suggestive of this individual ancestor?
Now of course, that the level of melanin in the eyes is the cause of this electromagnetic illusion of the eye, as noted in the earlier posts -- is understood, but when it is said that there is "limited" genetic variation...
2)then it has to be assumed that there are variations nonetheless, no?
3) Is not possible that more variations allow for the amount of melanin that impart the electromagnetic illusion of 'brownness' than that of "blue", and yet, imply that the latter need not necessarily be the product of a UEP?
Last but not least,
4)Was the sampling sufficiently comprehensive globally; and if so, are we told anything about the makeup of this comprehensive global sampling that had been undertaken?
Of course, the mutation began in Africa and part of the Albinism gene. Blue eyes are a defect associated with minimal melanin production due to OCA1 & 2 Albinism.
As with skin, melanin is present in the eye to accomplish two main functions. One, to protect the eye from damage by free radicals. Two, to convert radiation to electrical impulse. The decrease in melanin adversely affects both of these primary functions. This is true with either African Albinos or Europeans.
You may utilize and sampling of any population having Albinism. Blue/green/hazel eyes along with minimal to no skin melanin are primary detection symptom in Albinism. I hope this answers your questions.
As a matter of fact, your response tells me that you either didn't read my questions, or you didn't understand them. Hint: read the highlighted, and then re-read the questions that seek answers.
Posts: 7516 | From: Somewhere on Earth | Registered: Jan 2008
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Lol Meninarmer. The thing is none of the reports or scientists you've mentioned agree with you that all Europeans are albinos, or that albinos migrated from African into Europe. I don't know how many times this must be explained to you. Also, the MAYO report says the same exact thing as the medical site I've posted. None agree with you. lol.
Can you also answer my question of which genes causes brown eyes and what causes blue eyes?
Albinism is an inherited condition present at birth, characterized by a lack of pigment that normally gives color to the skin, hair, and eyes. Many types of albinism exist, all of which involve lack of pigment in varying degrees. The condition, which is found in all races, may be accompanied by eye problems and may lead to skin cancer later in life.
Description
Albinism is a rare disorder found in fewer than five people per 100,000 in the United States and Europe. Other parts of the world have a much higher rate; for example, albinism is found in about 20 out of every 100,000 people in southern Nigeria.
There are 10 types of the most common form of the condition, known as "oculocutaneous albinism," which affects the eyes, hair, and skin. In its most severe form, hair and skin remain pure white throughout life. People with a less severe form are born with white hair and skin, which turn slightly darker as they age. Everyone with oculocutaneous albinism experiences abnormal flickering eye movements (nystagmus) and sensitivity to bright light. There may be other eye problems as well, including poor vision and crossed or "lazy" eyes (strabismus).
The second most common type of the condition is known as "ocular" albinism, in which only the eyes lack color; skin and hair are normal. There are five forms of ocular albinism; some types cause more problems--especially eye problems--than others.
Causes and symptoms
Every cell in the body contains a matched pair of genes, one inherited from each parent. These genes act as a sort of "blueprint" that guides the development of a fetus.
Albinism is an inherited problem caused by a flaw in one or more of the genes that are responsible for directing the eyes and skin to make melanin (pigment). As a result, little or no pigment is made, and the child's skin, eyes and hair may be colorless.
In most types of albinism, a recessive trait, the child inherits flawed genes for making melanin from both parents. Because the task of making melanin is complex, there are many different types of albinism, involving a number of different genes.
It's also possible to inherit one normal gene and one albinism gene. In this case, the one normal gene provides enough information in its cellular blueprint to make some pigment, and the child will have normal skin and eye color. They "carry" one gene for albinism. About one in 70 people are albinism carriers, with one flawed gene but no symptoms; they have a 50% chance of passing the albinism gene to their child. However, if both parents are carriers with one flawed gene each, they have a 1 in 4 chance of passing on both copies of the flawed gene to the child, who will have albinism. (There is also a type of ocular albinism that is carried on the X chromosome and occurs almost exclusively in males because they have only one X chromosome and, therefore, no other gene for the trait to override the flawed one.)
Symptoms of albinism can involve the skin, hair, and eyes. The skin, because it contains little pigment, appears very light, as does the hair.
Although people with albinism may experience a variety of eye problems, one of the myths about albinism is that it causes people to have pink or red eyes. In fact, people with albinism can have irises varying from light gray or blue to brown. (The iris is the colored portion of the eye that controls the size of the pupil, the opening that lets light into the eye.) If people with albinism seem to have reddish eyes, it's because light is being reflected from the back of the eye (retina) in much the same way as happens when people are photographed with an electronic flash.
People with albinism may have one or more of the following eye problems:
* They may be very far-sighted or near-sighted, and may have other defects in the curvature of the lens of the eye (astigmatism) that cause images to appear unfocused.
* They may have a constant, involuntary movement of the eyeball called nystagmus.
* They may have problems in coordinating the eyes in fixing and tracking objects (strabismus), which may lead to an appearance of having "crossed eyes" at times. Strabismus may cause some problems with depth perception, especially at close distances.
* They may be very sensitive to light (photophobia) because their irises allow "stray" light to enter their eyes. It's a common misconception that people with albinism shouldn't go out on sunny days, but wearing sunglasses can make it possible to go outside quite comfortably.
In addition to the characteristically light skin and eye problems, people with a rare form of albinism called Hermansky-Pudlak Syndrome (HPS) also have a greater tendency to have bleeding disorders, inflammation of the large bowel (colitis), lung (pulmonary) disease, and kidney (renal) problems.
Diagnosis
It's not always easy to diagnose the exact type of albinism a person has; there are two tests available that can identify only two types of the condition. Recently, a blood test has been developed that can identify carriers of the gene for some types of albinism; a similar test during amniocentesis can diagnose some types of albinism in an unborn child. A chorionic villus sampling test during the fifth week of pregnancy may also reveal some types of albinism.
The specific type of albinism a person has can be determined by taking a good family history and examining the patient and several close relatives.
The "hairbulb pigmentation test" is used to identify carriers by incubating a piece of the person's hair in a solution of tyrosine, a substance in food which the body uses to make melanin. If the hair turns dark, it means the hair is making melanin (a "positive" test); light hair means there is no melanin. This test is the source of the names of two types of albinism: "ty-pos" and "ty-neg."
The tyrosinase test is more precise than the hairbulb pigmentation test. It measures the rate at which hair converts tyrosine into another chemical (DOPA), which is then made into pigment. The hair converts tyrosine with the help of a substance called "tyrosinase." In some types of albinism, tyrosinase doesn't do its job, and melanin production breaks down.
Treatment
There is no treatment that can replace the lack of melanin that causes the symptoms of albinism. Doctors can only treat, not cure, the eye problems that often accompany the lack of skin color. Glasses are usually needed and can be tinted to ease pain from too much sunlight. There is no cure for involuntary eye movements (nystagmus), and treatments for focusing problems (surgery or contact lenses) are not effective in all cases.
Crossed eyes (strabismus) can be treated during infancy, using eye patches, surgery or medicine injections. Treatment may improve the appearance of the eye, but it can do nothing to cure the underlying condition.
Patients with albinism should avoid excessive exposure to the sun, especially between 10 a.m. and 2 p.m. If exposure can't be avoided, they should use UVA-UVB sunblocks with an SPF of at least 20. Taking beta- carotene may help provide some skin color, although it doesn't protect against sun exposure.
Prognosis
In the United States, people with this condition can expect to have a normal lifespan. People with albinism may experience some social problems because of a lack of understanding on the part of others. When a member of a normally dark-skinned ethnic group has albinism, he or she may face some very complex social challenges.
One of the greatest health hazards for people with albinism is excessive exposure to sun without protection, which could lead to skin cancer. Wearing opaque clothes and sunscreen rated SPF 20, people with albinism can safely work and play outdoors safely even during the summer.
Prevention
Genetic counseling is very important to prevent further occurrences of the conditon.
For Your Information
Resources
Books
* National Association for the Visually Handicapped. Larry: A Book for Children with Albinism Going to School. New York: National Association for the Visually Handicapped.
Organizations
* Albinism World Alliance.
* American Foundation for the Blind. 15 W. 16th St., New York, NY 10011. (800) AFB-LIND.
* Hermansky-Pudlak Syndrome Network, Inc. One South Road, Oyster Bay, NY 11771-1905. (800) 789-9477. appell@theonramp.net.
* National Organization for Albinism and Hypopigmentation (NOAH). 1530 Locust St., #29, Philadelphia, PA 19102-4415. (800) 473-2310.
Gale Encyclopedia of Medicine, Published December, 2002 by the Gale Group The Essay Author is Carol A. Turkington.
Posts: 6572 | From: N.Y.C....Capital of the World | Registered: Jun 2008
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posted
^ Sorry, I don't understand your question. It's as if you completely ignore that the OCA coding for color "blue" would be a mutation, which the article fails to state. If it is a mutation (which it is), than there are bound to be wide variations. In fact, the variance can be as wide as An Black skinned person with blue eyes, to a Whitened black person with dark brown eyes.
The article also fails to mention that the only real conclusion can be is that OCA is not solely responsible for early eye formation, but rather, an additional set of varying permutations.
The eye needs melanin pigment to develop normal vision. People with albinism have impairment of vision because the eye does not have a normal amount of melanin pigment during development. Melanin forms in a special cell called the melanocyte. This cell is found in the skin, in the hair follicle, and in the iris and retina of the eye. There are many steps in the process of converting the amino acid tyrosine to melanin pigment. As with most metabolic pathways in our body, the first compound in a pathway is converted to the next compound by the action of an enzyme. For example, in the simple pathway A-->B-->C, the conversion of compound A to B occurs because of the action of Enzyme 1, and the conversion of B to C occurs because of the action of Enzyme 2. The formation of melanin pigment follows a pathway like this, but the pathway is more complex and not all of the steps are known. Tyrosinase (tie-ROW-sin-ace) is the major enzyme involved in the formation of melanin pigment. Tyrosinase is responsible for converting tyrosine to DOPA and on to dopaquinone (dopa-QUIN-own). The dopaquinone then forms black-brown eumelanin or red-yellow pheomelanin. The tyrosinase enzyme is made by the tyrosinase gene on chromosome 11, and alterations (also called mutations) of this gene can produce one type of albinism because the tyrosinase enzyme made by the altered gene does not work correctly. Two additional enzymes called tyrosinase-related protein 1 or DHICA oxidase (DEE-ca OX-eye-dase) and tyrosinase-related protein 2 or dopachrome tautomerase (dopa-chrome tow-TOM-er-ace) are important in the formation of eumelanin pigment. The gene for DHICA oxidase in on chromosome 9 and the gene for dopachrome tautomerase in on chromosome 9. Alterations of the DHICA oxidase gene are associated with a loss of function of this enzyme and this produces on type of albinism. Alterations of the gene for dopachrome tautomerase do not produce albinism. Three other genes make proteins that are also involved in melanin pigment formation and albinism, but the exact role of these proteins remains unknown. These genes are the P gene on chromosome 15, the Hermansky-Pudlak syndrome gene on chromosome 10, and the ocular albinism gene on the X chromosome.
Of course, the mutation began in Africa and part of the Albinism gene.
Good; this seems like the first genuine attempt to answer *one* of the questions asked above. The follow up question now is, according to whom, and how was the conclusion attained?
I see that the only other effort to answer another *one* of the questions, comes in the form of the following, citing only that which matters to my questionaire...
quote:Originally posted by Knowledgeiskey718:
quote:Originally posted by Explorateur:
quote: Originally posted by Knowledgeiskey718:
ScienceDaily (Jan. 31, 2008) — New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today....
The “switch”, which is located in the gene adjacent to OCA2 does not, however, turn off the gene entirely, but rather limits its action to reducing the production of melanin in the iris – effectively “diluting” brown eyes to blue.
Limited genetic variation
Variation in the colour of the eyes from brown to green can all be explained by the amount of melanin in the iris, but blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes. “From this we can conclude that all blue-eyed individuals are linked to the same ancestor,” says Professor Eiberg. “They have all inherited the same switch at exactly the same spot in their DNA.” Brown-eyed individuals, by contrast, have considerable individual variation in the area of their DNA that controls melanin production.
Questions:
1)Where did this genetic mutation in a single common ancestor occur?
Are we to assume that the girl below, shares this same common ancestor with a pale-skin blue eyed person, as exemplified in the image below, i.e. that of some pale-skin person's eye?
If so, what are we told about the uniparental marker that is strongly suggestive of this individual ancestor?
Now of course, that the level of melanin in the eyes is the cause of this electromagnetic illusion of the eye, as noted in the earlier posts -- is understood, but when it is said that there is "limited" genetic variation...
2)then it has to be assumed that there are variations nonetheless, no?
3) Is not possible that more variations allow for the amount of melanin that impart the electromagnetic illusion of 'brownness' than that of "blue", and yet, imply that the latter need not necessarily be the product of a UEP?
Last but not least,
4)Was the sampling sufficiently comprehensive globally; and if so, are we told anything about the makeup of this comprehensive global sampling that had been undertaken?
...Anyway, As we can it states in the article, I figure they tested the places where are blue eyes are most common.
quote: Professor Eiberg and his team examined mitochondrial DNA and compared the eye colour of blue-eyed individuals in countries as diverse as Jordan, Denmark and Turkey . His findings are the latest in a decade of genetic research, which began in 1996, when Professor Eiberg first implicated the OCA2 gene as being responsible for eye colour.
....Indeed it does seem they only tested individuals from Jordan, Denmark and Turkey.
It is fair to question whether a sample from Jordan, Denmark and Turkey is comprehensive enough to draw wide-ranging conclusions about the whereabouts and the time of origin of the "blue eye" trait, and no less so, linking that to a single common ancestor, don't you think? Or is there more to be said here about the sampling apparatus, implying that these three abovementioned were just the subjects of a quick blurting of examples of what was studied?
Posts: 7516 | From: Somewhere on Earth | Registered: Jan 2008
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quote:Originally posted by meninarmer: ^ Sorry, I don't understand your question. It's as if you completely ignore that the OCA coding for color "blue" would be a mutation, which the article fails to state.
How does one ignore that which one *already* knows? You'd know this, if you had bothered to read what was already posted in 1)my post of questionaire, and 2)not to mention, the posts in the thread itself *prior* to your own very first post here.
Posts: 7516 | From: Somewhere on Earth | Registered: Jan 2008
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posted
^ LOL, the article is from Science Daily. A publication as credible as National Geographic in regards to spin. Having read it, I'd say; it's carefully spun.
Posts: 3595 | From: Moved To Mars. Waiting with shotgun | Registered: Dec 2006
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posted
Indeed it is kinda weary to draw a conclusion on world populations for a single recent common ancestor for all blue eyed individuals. As soon as you asked I became curious. I think I will have to find a study in reference to Africans tested for blue eyes. As mentioned, the gene that causes the blue/brown have been identified as three different changes in the OCA2 gene that leads to blue eyes. In terms of eye color, OCA2 comes in two versions—brown (B) and blue (b). The brown version works in the stroma, while the blue version does not. Since the blue version doesn’t work there, no melanin builds up. So these individuals end up having blue eyes.
The fact that genes associated with OCA2 are the cause of brown as well as blue eyes, I'd take it the gene is present in all humans as well. Being that Africa is the home of modern humans for over 150kya, there definitely could have been earlier cases in which this OCA2 version for brown eyes didn't work in the stroma of the eye. As we can see albinism certainly arose in Africa, albeit the non working version for brown eyes does not mean the person is an albino though. As we can see from the girl in the pic you posted.
As per the article, here is the abstract and sampling methods.
The human eye color is a quantitative trait displaying multifactorial inheritance. Several studies have shown that the OCA2 locus is the major contributor to the human eye color variation. By linkage analysis of a large Danish family, we finemapped the blue eye color locus to a 166 Kbp region within the HERC2 gene. By association analyses, we identified two SNPs within this region that were perfectly associated with the blue and brown eye colors: rs12913832 and rs1129038. Of these, rs12913832 is located 21.152 bp upstream from the OCA2 promoter in a highly conserved sequence in intron 86 of HERC2. The brown eye color allele of rs12913832 is highly conserved throughout a number of species. As shown by a Luciferase assays in cell cultures, the element significantly reduces the activity of the OCA2 promoter and electrophoretic mobility shift assays demonstrate that the two alleles bind different subsets of nuclear extracts. One single haplotype, represented by six polymorphic SNPs covering half of the 3′ end of the HERC2 gene, was found in 155 blue-eyed individuals from Denmark, and in 5 and 2 blue-eyed individuals from Turkey and Jordan, respectively. Hence, our data suggest a common founder mutation in an OCA2 inhibiting regulatory element as the cause of blue eye color in humans. In addition, an LOD score of Z = 4.21 between hair color and D14S72 was obtained in the large family, indicating that RABGGTA is a candidate gene for hair color.
Material and methods
A three-generation Danish family (CFB#694) representing 28 informative meioses was used for linkage analysis and the blue eye color locus was finemapped. The family used in the linkage analysis, association and haplotype studies were of Danish origin and retrieved from the Copenhagen Family Bank, the families used in this study (families CFB#604-1505) (Eiberg et al. 1989). Only families with siblings, who had blue and brown eyes, respectively, were included in the study. The parents and siblings were classified as blue-eyed (Fig. 1a) or brown-eyed (Fig. 1c or d) individuals. Haplotypes were constructed from 100 Danish informative selected trios families, and most of these parents were also included in the association studies. These 100 triosis represented 45 families where at least one individual had brown eyes and 55 families where all individuals had blue eyes. Families where green and brown eye color spots segregate were not used. The haplotypes were deduced manually from the family study. Additional control material for DNA sequencing was collected from two large Danish families from the Copenhagen Family Bank. Five individuals from Turkey with blue eyes, black hair and light skin and two individual from Jordan with blue eyes, black hair and dark skin were included in the association analysis. Additionally, two persons with natal heterochromia were examined. The blue eye color phenotype was defined as a complete lack of brown pigmentation (Fig. 1a), an intermediate phenotype was defined as “blue eye with blown dots” (Fig. 1b), an intermediate brown eye color phenotype was defined as hazel with a broad peripupillary ring and was named the BEY1 phenotype (Fig. 1c), and a complete brown pigmented eye color was defined as the BEY2 phenotype (Fig. 1d).
All individuals in the study were interviewed by questionnaires and asked to determine their own eye color from the categories: brown, blue, gray and green, and whether brown spots or brown peripupillar rings were present.
Hair colors were categorized as red, black, brown and blond hair at the time when the persons were between 20 and 30 years of age. In family CFB#694, the eye color for all individuals was documented by photos and all key persons were re-examined. All individuals with green eye color or blue or gray eye color with brown spots not located close to the pupil were excluded from the linkage and association studies. Genomic DNA was extracted from the whole blood using standard phenol/chloroform procedures and the study adhered to the tenets of the declaration of Helsinki.
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quote:Originally posted by meninarmer: ^ Sorry, I don't understand your question. It's as if you completely ignore that the OCA coding for color "blue" would be a mutation, which the article fails to state.
How does one ignore that which one *already* knows? You'd know this, if you had bothered to read what was already posted in 1)my post of questionaire, and 2)not to mention, the posts in the thread itself *prior* to your own very first post here.
If you knew it, why did you ask?
Posts: 3595 | From: Moved To Mars. Waiting with shotgun | Registered: Dec 2006
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posted
^^^^can you please explain what the spin in the article from science daily was, and can you also answer my question of which genes causes brown eyes and what causes blue eyes?
Posts: 6572 | From: N.Y.C....Capital of the World | Registered: Jun 2008
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quote:Originally posted by Knowledgeiskey718: ^^^^can you please explain what the spin in the article from science daily was, and can you also answer my question of which genes causes brown eyes and what causes blue eyes?
The tyrosinase enzyme is made by the tyrosinase gene on chromosome 11, and alterations (also called mutations) of this gene can produce one type of albinism because the tyrosinase enzyme made by the altered gene does not work correctly. Two additional enzymes called tyrosinase-related protein 1 or DHICA oxidase (DEE-ca OX-eye-dase) and tyrosinase-related protein 2 or dopachrome tautomerase (dopa-chrome tow-TOM-er-ace) are important in the formation of eumelanin pigment. The gene for DHICA oxidase in on chromosome 9 and the gene for dopachrome tautomerase in on chromosome 9. Alterations of the DHICA oxidase gene are associated with a loss of function of this enzyme and this produces on type of albinism. Alterations of the gene for dopachrome tautomerase do not produce albinism. Three other genes make proteins that are also involved in melanin pigment formation and albinism, but the exact role of these proteins remains unknown. These genes are the P gene on chromosome 15, the Hermansky-Pudlak syndrome gene on chromosome 10, and the ocular albinism gene on the X chromosome.
Posts: 3595 | From: Moved To Mars. Waiting with shotgun | Registered: Dec 2006
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posted
Again, this shows you don't read, or don't understand what you read. **In terms of eye color, OCA2 comes in two versions—brown (B) and blue (b). The brown version works in the stroma, while the blue version does not.** Since the blue version doesn’t work there, no melanin builds up. So these individuals end up having blue eyes. OCA2 isn’t just involved in eye color. When it is completely broken, you end up with something called P-gene related oculocutaneous albinism.(Which is what you're talking about) This is a form of albinism more common in Africans than in Europeans.
Posts: 6572 | From: N.Y.C....Capital of the World | Registered: Jun 2008
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quote:Originally posted by meninarmer: ^ Sorry, I don't understand your question. It's as if you completely ignore that the OCA coding for color "blue" would be a mutation, which the article fails to state.
How does one ignore that which one *already* knows? You'd know this, if you had bothered to read what was already posted in 1)my post of questionaire, and 2)not to mention, the posts in the thread itself *prior* to your own very first post here. [/qb]
If you knew it, why did you ask?
Why did I ask what specifically, and how did you answer it accordingly? You answered what was not asked, and totally avoided that which was asked. So the question should be, why do you answer what you were not asked to begin with, and dodged that which was asked?
Posts: 7516 | From: Somewhere on Earth | Registered: Jan 2008
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quote:Originally posted by Knowledgeiskey718: Again, this shows you don't read, or don't understand what you read. **In terms of eye color, OCA2 comes in two versions—brown (B) and blue (b). The brown version works in the stroma, while the blue version does not.** Since the blue version doesn’t work there, no melanin builds up. So these individuals end up having blue eyes. OCA2 isn’t just involved in eye color. When it is completely broken, you end up with something called P-gene related oculocutaneous albinism.(Which is what you're talking about) This is a form of albinism more common in Africans than in Europeans.
^ I'd strongly suggest you read more.
Melanin is produced in two versions, black and red. There is no "blue" pigment, only color mixes of the two primary melanin versions plus a third white base, light Your Doctor above is incorrect describing color gene balancing as a "on"/"off" switch in a digital sense. Rather, it is much more accurately described as a "Fuzzy" switch, where the gene may allow many active states between on and off. Therefore, each gene expression acts more like a flow valve, each being capable of being full open to full closed and many increments in between, more analog in nature than digital.
See above chart, and you can relate each gene in the sequence of pigment formation. The error (mutation) may be in any or or more genes in the sequence, as well as also affected by other factors. Melanin in the human skin, hair and eyes can be classified into two groups: black to brown eumelanin (EM) and yellow to red pheomelanin (PM)
Characterization of melanin in human iridal and choroidal melanocytes from eyes with various colored irides
Kazumasa Wakamatsu 1 , Dan-Ning Hu 2 , Steven A. McCormick 2 , Shosuke Ito 1* 1 Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi, Japan 2 Tissue Culture Center, Departments of Pathology and Ophthalmology, The New York Eye and Ear Infirmary, New York Medical College, New York, NY, USA *Address correspondence to Shosuke Ito, e-mail: sito@fujita-hu.ac.jp Copyright 2007 The Authors, Journal Compilation 2007 Blackwell Munksgaard
Type and quantity of melanin in growing uveal melanocytes from eyes with various colored irides
In growing uveal melanocytes, the quantity of EM was correlated with iris color (Figure 2A). Uveal melanocytes from eyes with dark-colored irides (dark brown and brown irides) contained a significantly greater quantity of EM than that of cells from eyes with light-colored irides (blue, yellow-brown, green and hazel colored irides) (P less than 0.0001). A similar, but less pronounced difference was observed between dark brown and brown irides (P less than 0.05). The quantity of PM in uveal melanocytes from eyes with light-colored irides was slightly greater than that from dark-colored irides, although this was not statistically significant (Figure 2A). EM/PM ratio in uveal melanocytes was also related to iris color; the darker the iris color, the higher EM/PM ratio (Figure 2A). This indicates that darker melanocytes produce not only a higher quantity of melanin but also more eumelanic pigment than lighter melanocytes; melanocytes from dark brown irides contain 93% EM while those from blue irides contain only 44%. The total quantity of melanin (either EM + PM or TM) measured by HPLC or spectrophotometry, respectively, also correlated with iris color (Figure 2A). EM + PM and TM values in uveal melanocytes from eyes with dark-colored irides were greater than those from eyes with light-colored irides, and the difference was statistically significant (P less than 0.0001) (Figure 2A).
Variance in iris color is related to the incidence of several important ocular diseases, including uveal melanoma and age-related macular degeneration. The purposes of this study were to determine the quantity and the types of melanin in cultured human uveal melanocytes in relation to the iris color. Sixty-one cell cultures of pure uveal melanocytes were isolated from donor eyes with various iris colors. The amount of eumelanin (EM) and pheomelanin (PM) of these cells was measured by chemical degradation and microanalytical high-performance liquid chromatography (HPLC) methods. The total amount of melanin was measured by both microanalytical methods and spectrophotometry. Total melanin content, measured by HPLC and spectrophotometry, correlated well with r = 0.872 (P less than 0.0001). The quantity and type of melanin in iridal and choroidal melanocytes showed no significant difference (P greater than 0.05). When cells became senescent, the levels of EM, PM and total melanin were significantly increased. In both growing and senescent melanocytes, the quantity and type of melanin were closely correlated to the iris color. In cells from eyes with dark-colored irides (dark brown and brown), the amount of EM, the ratio of EM/PM and total melanin were significantly greater than that from eyes with light-colored irides (hazel, green, yellow-brown and blue) (P less than 0.0001). The quantity of PM in uveal melanocytes from eyes with light-colored irides was slightly greater than that from dark-colored irides, although not statistically significant (P greater than 0.05). The present study shows that iris color is determined by both the quantity and the type of melanin in uveal melanocytes. These results suggest a possibility that uveal melanin in eyes with dark-colored irides is eumelanic at the surface and acts as an antioxidant while that in eyes with light-colored irides exposes pheomelanic core and behaves as a pro-oxidant.
Posts: 3595 | From: Moved To Mars. Waiting with shotgun | Registered: Dec 2006
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Indeed it is kinda weary to draw a conclusion on world populations for a single recent common ancestor for all blue eyed individuals. As soon as you asked I became curious.
Well, the point is not just taking things at face value, until the details are well understood.
Posts: 7516 | From: Somewhere on Earth | Registered: Jan 2008
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Indeed it is kinda weary to draw a conclusion on world populations for a single recent common ancestor for all blue eyed individuals. As soon as you asked I became curious.
Well, the point is not just taking things at face value, until the details are well understood.
Point taken and understood.
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quote:Originally posted by meninarmer: [QUOTE]Originally posted by Knowledgeiskey718: [qb] Again, this shows you don't read, or don't understand what you read. **In terms of eye color, OCA2 comes in two versions—brown (B) and blue (b). The brown version works in the stroma, while the blue version does not.** Since the blue version doesn’t work there, no melanin builds up. So these individuals end up having blue eyes. OCA2 isn’t just involved in eye color. When it is completely broken, you end up with something called P-gene related oculocutaneous albinism.(Which is what you're talking about) This is a form of albinism more common in Africans than in Europeans.
^ I'd strongly suggest you read more.
Melanin is produced in two versions, black and red.
The two versions of the OCA2 blue and brown, the colors are in reference to the eye color. Obviously you need to read more and thoroughly to understand more clearly. You're always answering something incorrectly or distracting with something else that has nothing to do with the topic. Due to your misunderstanding.
Btw, how do you propose all Europeans turned albino again?
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