While trying to locate information on whether hair colour lightens skin tone, I found a few articles suggesting that eye colour does, blue eyes particularly. Here’s a couple of studies I’ve found. From what I’ve read, it seems that several recessive genes (red hair, blue eyes) lighten skin colour. It’s not totally clear if it’s just through geographical association with other genes though.
Skin pigmentation, biogeographical ancestry and admixture mapping
Mark D. Shriver, Esteban J. Parra, Sonia Dios, Carolina Bonilla, Heather Norton, Celina Jovel, Carrie Pfaff, Cecily Jones, Aisha Massac, Neil Cameron, Archie Baron, Tabitha Jackson, George Argyropoulos, Li Jin, Clive J. Hoggart, Paul M. McKeigue, Rick A. Kittles
Ancestry informative markers (AIMs) are genetic loci showing alleles with large frequency differences between populations. AIMs can be used to estimate biogeographical ancestry at the level of the population, subgroup (e.g. cases and controls) and individual. Ancestry estimates at both the subgroup and individual level can be directly instructive regarding the genetics of the phenotypes that differ qualitatively or in frequency between populations. These estimates can provide a compelling foundation for the use of admixture mapping (AM) methods to identify the genes underlying these traits. We present details of a panel of 34 AIMs and demonstrate how such studies can proceed, by using skin pigmentation as a model phenotype. We have genotyped these markers in two population samples with primarily African ancestry, viz. African Americans from Washington D.C. and an African Caribbean sample from Britain, and in a sample of European Americans from Pennsylvania. In the two African population samples, we observed significant correlations between estimates of individual ancestry and skin pigmentation as measured by reflectometry (R2=0.21, P<0.0001 for the African-American sample and R2=0.16, P<0.0001 for the British African-Caribbean sample). These correlations confirm the validity of the ancestry estimates and also indicate the high level of population structure related to admixture, a level that characterizes these populations and that is detectable by using other tests to identify genetic structure. We have also applied two methods of admixture mapping to test for the effects of three candidate genes (TYR, OCA2, MC1R) on pigmentation. We show that TYR and OCA2 have measurable effects on skin pigmentation differences between the west African and west European parental populations. This work indicates that it is possible to estimate the individual ancestry of a person based on DNA analysis with a reasonable number of well-defined genetic markers. The implications and applications of ancestry estimates in biomedical research are discussed.
OCA2 controls eye colour, and TYR is a gene that harbours mutations for albinism. This seems to suggest that lighter eye colour could lead to lighter skin colour too. You see this in albino Africans, with partial albinism. They sometimes have blond hair and blue eyes, not the white hair and pink eyes of a full albino.
I’m sure Razib said something about that on his blog…
|Fair skin||Medium skin||Olive skin|
Please excuse the plagiarism. Full blog item here.
The paper he ‘s quoting from…
We have previously shown that a quantitative-trait locus linked to the OCA2region of 15q accounts for 74% of variation in human eye color. We conducted additional genotyping to clarify the role of the OCA2locus 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 OCA2SNPs: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 rs11855019C/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 non-blue 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.
And a more recent addition.
Interactions Between HERC2, OCA2 and MC1R May Influence Human Pigmentation Phenotype
Annals of Human Genetics doi:10.1111/j.1469-1809.2009.00504.x, Wojciech Branicki et al.
Human pigmentation is a polygenic trait which may be shaped by different kinds of gene–gene interactions. Recent studies have revealed that interactive effects between HERC2 and OCA2 may be responsible for blue eye colour determination in humans. Here we performed a population association study, examining important polymorphisms within the HERC2 and OCA2 genes. Furthermore, pooling these results with genotyping data for MC1R, ASIP and SLC45A2 obtained for the same population sample we also analysed potential genetic interactions affecting variation in eye, hair and skin colour. Our results confirmed the association of HERC2 rs12913832 with eye colour and showed that this SNP is also significantly associated with skin and hair colouration. It is also concluded that OCA2 rs1800407 is independently associated with eye colour. Finally, using various approaches we were able to show that there is an interaction between MC1R and HERC2 in determination of skin and hair colour in the studied population sample.
Anyone interested in this might be interested in Razibs more in depth look at this here
This is my all time number one post on this blog, about ten percent of hits have come from this. Lord only knows why but about 150 people a day look at it. Why this one?