Red-haired individuals most commonly are R/ R genotype, and this genotype accounts for as much as 84% of red hair colour, but R/ r, R/+ and r/ r genotypes can also result in red hair. The commonest variants in MC1R have been characterised as highly penetrant or low penetrant red hair alleles and classified as R or r, respectively. Presently, more than 70 variations in MC1R have been reported. Red hair colour was initially attributed to MC1R variation by association studies but the highly penetrant phenotype of some variants subsequently allowed family studies. Thus, for example, brown eye and hair colour was mapped to chromosome 15 by linkage and was also found associated with SNPs in the OCA2, and adjacent HERC2 genes in both whole genome and candidate studies. Both linkage studies in families and genome-wide association studies in populations have identified genetic factors that determine hair and eye colour. Blond and red hair colours are commonly seen variations in Europeans, but are rare in other populations. In Europeans, genetic factors explain 92% of the variation in hair colour, while most of the rest of the variation is due to environmental influence.
Short black hair brown eyes female skin#
Whilst variation in skin pigmentation is notable between populations, hair colour variation is most notable within populations of European origin. The colours of hair, skin and eyes provide some of the most visible variation between and within human populations. However, although this replicated in the smaller cohort of the Danish population, no association was seen when the whole study population was analysed. A previously unreported association with the HPS3 gene was seen in the Scottish population. The Danish analysis excluded those with red hair, and no associations were found with MC1R in this group, emphasising that MC1R regulates the colour rather than the intensity of pigmentation. MC1R variation correlated, as expected, with the red dimension of colorimetric hair colour in Scots. We found replicable associations of hair colour with the KITLG and OCA2 genes. The Danish population was also genotyped with SNPs in 4 previously described pigmentation genes. Associations found between SNPs and colorimetric hair data and eye colour categories were replicated in a cohort of the Danish population. DNA from the Scottish group was genotyped at SNPs in 33 candidate genes, using 384 SNPs identified by HapMap as representatives of each gene. Both cohorts were also assessed for eye colour. The Danish population was assigned into categorical hair colour groups. Cluster analysis of this data defined two groups, with overlapping borders, which corresponded to visually assessed dark versus red/light hair colour.
We assayed the hair of a population of individuals of Scottish origin using tristimulus colorimetry, in order to produce a quantitative measure of hair colour.
0 kommentar(er)
