All blue-eyed people have a common ancestor
Scientists at the University of Copenhagen have traced a genetic mutation that occurred 6-10 thousand years ago and provides the eye color of all living blue-eyed people.
According to the head of the work, Professor Eiberg, initially all people had brown eyes. However, a mutation affecting the activity of the OCA2 gene changed the situation. The OCA2 gene encodes the protein P (P protein) involved in the synthesis of melanin, a pigment that provides the color of human skin, hair and eyes. With complete inactivation of this gene, albinism is observed – a condition in which there is no melanin in the body. The mutation that resulted in blue-eyed people occurred in a gene adjacent to the OCA2 gene, which led to selective suppression of melanin synthesis in the iris of the descendants of the first carrier of this mutation.
Variations in eye color from dark brown to green can be explained by the amount of melanin in the iris. In blue-eyed people, the level of melanin in the iris is limited and varies in a very narrow range. Such people inherit the genetic "switch" of enzyme synthesis strictly at the same point in DNA, whereas brown-eyed people have a large number of genetic variations in the DNA region controlling melanin synthesis.
As part of the work started in 1996, when Professor Aiberg first established that the OCA2 gene determines eye color, the authors analyzed mitochondrial DNA and compared the eye color of blue-eyed individuals living in different countries, including as far apart as Denmark and Turkey with Jordan.
The mutation, as a result of which brown eyes turned into blue, is neither positive nor negative. Mutations of this kind include hereditary changes that provide hair color, the severity of vegetation, freckles and moles, which do not affect the chances of survival of the organism in any way. The results obtained by the authors are another proof that nature continuously makes changes to the human genome, creating a "genetic cocktail" of chromosomes and testing the viability and functionality of various changes.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily.
04.02.2008