Iris Genetics

Abstract

The genetics and inheritance of the iris regarding its morphology and color is very complex since it is involved in many different genes and their interactions. Recently discovery of SNP (single nucleotide polymorphism) in intron 86 of the gene HERC2 has been discovered. C allele at "rs12913832" leads to decreased expression of OCA2 in blue eyes. Multiple factors are involved in eye color variations and will be discussed in brief, the detailed data and information is way above the scope of this book. The summarized and simplified version is being discussed in this chapter and references are provided for more comprehensive insight to this fast evolving field of science. Discussion As the genetic field of science is in a fast evolving with new sequencing technologies and ongoing discoveries that make more information being available as time goes by. There is a very good review of genetics of human color and patterns published by Strum & Larsson which is highly recommended [8]. At the time of the first human migrations out of Africa 60,000 years ago, our ancestral population had characteristic Dark skin, hair, and eye color to adapt to the high UV radiation around the equator. As the first settlements moved north away from the equator adaptive mutations happened in the genes carrying pigmentary regulations. There were advantages in the lighter pigments Pheomelanin (Orange/yellow) rather than Eumelanin (Dark Brown) and less pigmentation that helped better absorption of vitamin D which was crucial to their health. Blue-eyed people share a common ancestor, presumably 6000-10,000 years ago. A "switch" or a simple change from adenine to guanine mutation at HERC2 happened. This mutation directly affects OCA2 gene, which regulates the pigmentation