Wednesday, January 30, 2008

I'm Descended From a Blue-Eyed Mutant

Scientists at the University of Copenhagen say that all blue-eyed people—including me and every member of my immediate family—descend from a common ancestor, who lived six- to ten-thousand years ago.

“Originally, we all had brown eyes”, said Professor Eiberg from the Department of Cellular and Molecular Medicine. “But a genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a 'switch', which literally 'turned off' the ability to produce brown eyes”.
Variation in the colour of the eyes from brown to green can all be explained by the amount of melanin in the iris, but blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes. “From this we can conclude that all blue-eyed individuals are linked to the same ancestor,” says Professor Eiberg. “They have all inherited the same switch at exactly the same spot in their DNA.” [Link]


Aren't blue eyes a recessive trait, meaning the gene has to be inherited from both parents? How can we be descended from a single ancestor? Or even a single couple? I'm hoping my family tree branches a bit more than that. :)


I was wondering the same thing. I suppose that the trait could have been unexpressed through a few generations until a pair of cousins with the same recessive gene produced a blue-eyed child. In which case, the correct title of this post should be "I'm Descended From the Blue-Eyed Grandchild of a Mutant."

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