Humans have many phenotypic variations in eye color which is determined by multiple genes. So far, up to 16 genes have been associated with eye color inheritance. However, scientists from the Institute of Forensic Genetics at the University of Copenhagen discovered that the reason for blue eyes mainly lies in two genes: OCA2 and HERC2. This way they have shown that the earlier belief that blue eye color is a simple recessive trait is incorrect.

Originally, all humans had brown eyes, although genetic variation relating to a gene called OCA2 resulted in changes to the amount of pigment produced by different individuals, resulting in the emergence of different shades of brown eyes. Scientists studying the genetics of eye color have identified that a mutation to a separate, nearby gene called HERC2 is the cause of blue eyes. This alteration switches off OCA2, the gene that determines the amount of the brown pigment melanin that we make.

Today, around 20-40% of European people have blue eyes. Scientist discovered that more than 99.9 per cent of blue-eyed people who volunteered to have their DNA analyzed have the same tiny mutation in the gene that determines the color of the iris.

Scientists concluded that every blue-eyed person on the world today can trace their ancestry back to a single European who probably lived about 10,000 years ago in the Black Sea region and who first developed a specific mutation that accounts for the now widespread iris coloration.

Watch the video “Why Do You Have Blue Eyes?” which explains in a simple way the genetics of blue eyes. Enjoy!

By Katarina Kovac, PhD, BioSistemika LLC