"What they were able to show is that the people who have blue eyes in Denmark, as far as Jordan, these people all have this same haplotype, they all have exactly the same gene changes that are all linked to this one mutation that makes eyes blue," Hawks said in a telephone interview. The DNA sequence didn't have enough time to get mixed up. If a group of individuals shares long haplotypes, that means the sequence arose relatively recently in our human ancestors. Some of these segments, however, that haven't been reshuffled are called haplotypes. Over the course of several generations, segments of ancestral DNA get shuffled so that individuals have varying sequences. They specifically looked at sequences of DNA on the OCA2 gene and the genetic mutation associated with turning down melanin production. This genetic material comes from females, so it can trace maternal lineages. Hawks was not involved in the current study.Įiberg and his team examined DNA from mitochondria, the cells' energy-making structures, of blue-eyed individuals in countries including Jordan, Denmark and Turkey. "It's exactly what I sort of expected to see from what we know about selection around this area," said John Hawks of the University of Wisconsin-Madison, referring to the study results regarding the OCA2 gene. If the OCA2 gene had been completely shut down, our hair, eyes and skin would be melanin-less, a condition known as albinism. In effect, the turned-down switch diluted brown eyes to blue. The genetic switch is located in the gene adjacent to OCA2 and rather than completely turning off the gene, the switch limits its action, which reduces the production of melanin in the iris.
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