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Origin of Blue Eyes (Genetics)
"Originally, we all had brown eyes," said Hans Eiberg from the Department of Cellular and Molecular Medicine at the University of Copenhagen. The mutation
affected the so-called OCA2 gene, which is involved in the production
of melanin,
the pigment that gives color to our hair, eyes and skin. 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. In effect, the turned-down switch diluted brown eyes to blue. If the OCA2 gene had been completely shut down, our hair, eyes and skin would be melanin-less, a condition known as albinism. "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. Hawks was not involved in the current study. Baby blues They specifically looked at sequences of DNA on the OCA2 gene and the genetic mutation associated with turning down melanin production. Over the course of several generations, segments of ancestral DNA get shuffled so that individuals have varying sequences. Some of these segments, however, that haven't been reshuffled are called haplotypes. If a group of individuals shares long haplotypes, that means the sequence arose relatively recently in our human ancestors. The DNA sequence didn't have enough time to get mixed up. "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. Melanin switch "Out of 800 persons we have only found one person which didn't fit ? but his eye color was blue with a single brown spot," Eiberg told LiveScience, referring to the finding that blue-eyed individuals all had the same sequence of DNA linked with melanin production. "From this we can conclude that all blue-eyed individuals are linked to the same ancestor," Eiberg said. "They have all inherited the same switch at exactly the same spot in their DNA." Eiberg and his colleagues detailed their study in the Jan. 3 online edition of the journal Human Genetics. That genetic switch somehow spread throughout Europe and now other parts of the world. "The question really is, 'Why did we go from having nobody on Earth with blue eyes 10,000 years ago to having 20 or 40 percent of Europeans having blue eyes now?" Hawks said. "This gene does something good for people. It makes them have more kids." _____________________ This poses the following questions: 1) If the above applies
to blue and green eyes, is the same mutation responsible for
causing hazel colored eyes? 2) If this mutation occurred 6000
years ago, that was before Noah's flood, and if this happened
prior to 10,000 years ago was pre-Adam, so the estimation of
years must not be accurate; therefore, which of Noah's sons developed
this mutation that caused blue eyes and settled in Western Europe?
3) The article claims a single, common ancestor of all blue-eyed
people, but this conclusion is doubtful -- more likely, more
than one person simply had the mutation, and the mutation keeps
happening repeatedly with dominate versus recessive genetic traits.
4) The last comment, the mutated gene causing blue eyes also
causes people to have more children, might seem comical or in
jest, but might be a serious scientific observation; it could
also refer to blue-eyed blondes about whom we tend to make jokes,
but may have validity -- but it could be that the mutated gene
could be multiplying or happening in more people, not necessarily
causing increased numbers of children. 5) With the passage
of time and more genetic studies, geneticists will likely change
their opinions about why such mutations happened originally and
why the mutations continue to happen. |
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