Are all modern blue/green eyes from the same two mutations or have there been multipl

[Voight]

blue/green eye mutations throughout history?

 

[Sile]

blue/green eye mutations throughout history?

all green eyes come of of blue eyes , so does grey come of of blue

 

[ThirdTerm]

Two pigmentation genes called OCA2 and HERC2 on chromosome 15 are primarily responsible for human eye colors. Most East Asians only have the OCA2 gene and they naturally have brown eyes, while the frequency of HERC2 in East Asia is less than 2%. The HERC2 gene acts as a promoter of the OCA2 gene to trigger a change from brown to blue eyes. The frequencies of the HERC2 gene are more than 90% in northern Europe and less than 50% in southern Europe. The Nature paper (White and Rabago-Smith 2011) explains the mechanics behind human eye colors.

Allele frequencies of rs12913832 in human populations surveyed as part of the Human Genome Diversity Project. The SNP, rs12913832, is in the HERC2 gene.

Two major genes on chromosome 15 affect the quantity and quality of the melanin produced by melanogenesis. HERC2, a large ubiquitin ligase, contains the promoter region for OCA2, the P protein. When a T is replaced with a C in rs12913832 of intron 86, OCA2 transcription is depressed, resulting in a blue-eyed individual. This epistatic relationship demonstrates the significance of introns and how a single-base change greatly affects an aspect of the individual. OCA2 contains regions for the numerous eye colors, but one SNP is a strong predictor for brown/blue eyes. A change in rs1800407 causes a change in the protein, Arg419Gln, and a change from brown to blue eyes. Therefore, the residue change causes a problem with the P protein, and melanin maturation decreases. Aside from these two genes, the genes involved in melanogenesis and other minor genes also contain regions that account for eye color. Having little effect on eye color, many of them deal primarily with hair and skin pigmentation. Lastly, disorders involved in eye color include ocular albinism and heterochromia. Depending on how little pigment the melanocytes produce, albinism causes red or violet eyes. Producing multicolored irises, heterochromia stems from mutations in certain cells of the iris.
https://www.nature.com/articles/jhg2010126

 

[Voight]

@ThirdTerm

so is this HERC2 gene present in the few Africans who have light colored eyes as well? (i.e. are their light eyes a result of R1b coming down to central Africa or a separate mutation?)

 

[MOESAN]

here under
[h=2]Abstract[/h]Mutations in the gene OCA2 are responsible for oculocutaneous albinism type 2, but polymorphisms in and around OCA2 have also been associated with normal pigment variation. In Europeans, three haplotypes in the region have been shown to be associated with eye pigmentation and a missense SNP (rs1800407) has been associated with green/hazel eyes (Branicki et al. in Ann Hum Genet 73:160?170, 2009). In addition, a missense mutation (rs1800414) is a candidate for light skin pigmentation in East Asia (Yuasa et al. in Biochem Genet 45:535?542, 2007; Anno et al. in Int J Biol Sci 4, 2008). We have genotyped 3,432 individuals from 72 populations for 21 SNPs in the OCA2-HERC2 region including those previously associated with eye or skin pigmentation. We report that the blue-eye associated alleles at all three haplotypes were found at high frequencies in Europe; however, one is restricted to Europe and surrounding regions, while the other two are found at moderate to high frequencies throughout the world. We also observed that the derived allele of rs1800414 is essentially limited to East Asia where it is found at high frequencies. Long-range haplotype tests provide evidence of selection for the blue-eye allele at the three haplotyped systems but not for the green/hazel eye SNP allele. We also saw evidence of selection at the derived allele of rs1800414 in East Asia. Our data suggest that the haplotype restricted to Europe is the strongest marker for blue eyes globally and add further inferential evidence that the derived allele of rs1800414 is an East Asian skin pigmentation allele.

I'm not sure I understand well their vocabulary but it seems that these names HERC2 and OC2 applies to loci (places, regions) on the chromosome chain: it seems to me it's the variation of bases in the alleles placed in these loci and even the interaction of these loci that makes difference (action of HERC2 upon OCA2). I red there were more than a locus or bound loci for blond hair; for blue eye I don't know to date. I think we don't know the whole thing yet.

 

[Voight]

We report that the blue-eye associated alleles at all three haplotypes were found at high frequencies in Europe; however, one is restricted to Europe and surrounding regions, while the other two are found at moderate to high frequencies throughout the world..

So does this mean that these three "haplotypes" evolved from the same source or at entirely different contexts? I'm still not sure if this means that those central Africans with lighter eyes evolved the light eyes independently from everyone else

 

[Tutkun Arnaut]

Two pigmentation genes called OCA2 and HERC2 on chromosome 15 are primarily responsible for human eye colors. Most East Asians only have the OCA2 gene and they naturally have brown eyes, while the frequency of HERC2 in East Asia is less than 2%. The HERC2 gene acts as a promoter of the OCA2 gene to trigger a change from brown to blue eyes. The frequencies of the HERC2 gene are more than 90% in northern Europe and less than 50% in southern Europe. The Nature paper (White and Rabago-Smith 2011) explains the mechanics behind human eye colors.

Allele frequencies of rs12913832 in human populations surveyed as part of the Human Genome Diversity Project. The SNP, rs12913832, is in the HERC2 gene.

Nobody is talking about medium to light bro
wn eyes. I find that color very appealing​

 

[Tutkun Arnaut]

Medium to light brown eyes are also appealing

 

[MOESAN]

Before answer

[h=3]Table 3[/h] Definition of ?blue-eye? haplotypes (BEHs)

[TH="width: 117"]

Haplotype name​

[/TH]
[TH="width: 221"]

SNPs included​

[/TH]
[TH="width: 178"]

Blue-eye associated allele​

[/TH]

[TD="width: 117"]

BEH1​

[/TD]
[TD="width: 221"]

rs4778138, rs4778241, rs7495174​

[/TD]
[TD="width: 178"]

ACA​

[/TD]

[TD="width: 117"]

BEH2​

[/TD]
[TD="width: 221"]

rs1129038, rs12913832​

[/TD]
[TD="width: 178"]

TG​

[/TD]

[TD="width: 117"]

BEH3​

[/TD]
[TD="width: 221"]

rs916977, rs1667394​

[/TD]
[TD="width: 178"]

CA​

[/TD]

[h=3]Geographic distributions of haplotypes[/h] The distributions of the blue-eye associated alleles at the three haplotyped systems are presented in Fig. 2, each haplotype in contour plots, and all three grouped by population in a histogram. The actual frequencies are presented in supplemental material and in ALFRED. The alleles associated with blue eyes at all three BEH blue-eye associated haplotypes have their highest frequencies in Northwestern Europe, and the TG allele at BEH2 is essentially observed only in Europe; the ACA allele of BEH1 and the CA allele at BEH3 are at their highest frequencies in Europe, particularly in Northern and Western Europe, and have much lower frequencies elsewhere. In most of Central and East Asia, these alleles have frequencies of <20% but reach frequencies of 40% and higher in the Americas.
&: ME: would this say that one (earlier) of the immigration waves of Amerindians ancestors (today in East) had less southeast asian ancestry and more northern asian, with this unbroken ANE element in them and more ties with some ancestors of the westeurasians?


Global frequencies of blue-eye associated haplotypes. This figure shows the distributions of the blue-eye associated allele/haplotype at the respective BEH1 (a), BEH2 (b), and BEH3 (c) genetic systems graphed on a world map, as well as a comparison of the frequencies in a bar graph (d). In part d, the associated alleles are represented in yellow at BEH1, in blue at BEH2, and in red at BEH3. Here we see that the blue-eye associated allele of BEH2 is mostly limited to Europe, whereas the blue-eye associated alleles of BEH1 and BEH3 are found globally. The populations are divided by regional group on the x-axis as follows: Africa (yellow), Southwest Asia (green), Europe (blue), Central Asia (orange), Pacific Islands (purple), East Asia (red), and Native Americans (teal).

 

[MOESAN]

So does this mean that these three "haplotypes" evolved from the same source or at entirely different contexts? I'm still not sure if this means that those central Africans with lighter eyes evolved the light eyes independently from everyone else

As you can see on maps, "black" Africa shows almost NO mutation, except a gradiant in North possibly explained without difficulty by the input of Hamitic or Semitic pops of extreme East-Africa and Southwest Asia-Near East.
WHat appears at first sight is selective zones in North India Hindu Kush, northcentral Australia and some places of America (Indians): western Amazonia and Northeast plains; concerning Hindu Kush, we can rather suppose an ancient continuum between this regions and Eurasian Steppes, broken by Turkic invasions, recently in History. My point just after reading.
noteworthy: phenotypes among the non-European pops do'nt confirm genotype: so we can imagine the need of other mutated genes to help the depigmentation in eyes?