#Eye colors skin

#Eye colors skin

If we consider the new lactase persistence allele as an adaptive change in response to availability of dairy products (see Lactose Intolerance), then what is the adaptive significance of lighter skin and eyes? This could be explained by the need for maximized utilization of low level UV light (for vitamin D absorption) in high latitude European regions (see Skin Color). One interesting observation is that only European populations have developed a significant lightening of the pigmentation phenotypes of skin, hair and eye color traits due to genetic selection of multiple genes. In addition to eye color, melanin/melanocytes are also responsible for our hair and skin colors. It was later found that a set of six SNPs within OCA2-HERC2, SLC24A4, SLC45A2, TYR and IRF4 genes formed a very effective predictor of eye color, giving successful rate of 93% for brown, 91% for blue and 72% for intermediate eye color. Likelihood of eye color for people of European descent A person who has two copies of C allele at HERC2 rs1293832 will likely have blue eyes while homozygous TT predicts likely brown eyes. In the European population, a common polymorphism in HERC2 gene is responsible for the blue eye phenotype. HERC2 regulates the OCA2 genes’ expression. Mutations in OCA2 result in oculocutaneous albinism, a condition associated with vision problems such as reduced sharpness and increased sensitivity to light. The OCA2 gene produces a cell membrane transporter of tyrosine, a precursor of melanin. Among the genes that affect eye color, OCA2 and HERC2 stand out. It is now clear that eye color is a polygenic trait, meaning it is determined by multiple genes. It was originally thought that eye color was a simple Mendelian trait, meaning it was determined by a single gene, with brown being dominant and blue recessive. For example, United Arab Emirates (UAE) has been operating an iris scan system since 2001 at all ports of entry to screen for expellees. Some banks now use iris scans, instead of pin codes for identification and some countries are now using iris scans for border control purposes.

Just like one’s fingerprints, an iris pattern can be used for biometric identification. In addition to color, the fibrous tissue in the iris also forms a unique pattern in each individual’s eyes. In general, brown is the most common eye color, followed by blue, grey and then green.

In fact, iris color exists in a gradient of shades and color patterns: from the lightest shades of blue to the darkest browns and everything in between. For example, as light travels through a relatively melanin-free iris, collagen fibers within the iris scatter the short blue light to the surface creating the blue appearance of the iris. The amount of melanin found in your iris, in conjunction with white collagen fibers, produces different shades of grey, green and hazel. What we call eye color is actually the color of the iris. Human eyes are fascinating - just take a look at the many different shades of eye color and the intricate, unique iris patterns from all over the world.