Wednesday, January 28, 2015

Blue-eyed humans have a single, common ancestor


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.
Credit: iStockphoto/Cristian Ardelean
New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today.

What is the genetic mutation
"Originally, we all had brown eyes," said Professor Hans 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." The OCA2 gene codes for the so-called P protein, which is involved in the production of melanin, the pigment that gives colour to our hair, eyes and skin. The "switch," which is located in the gene adjacent to OCA2 does not, however, turn off the gene entirely, but rather limits its action to reducing the production of melanin in the iris -- effectively "diluting" brown eyes to blue. The switch's effect on OCA2 is very specific therefore. If the OCA2 gene had been completely destroyed or turned off, human beings would be without melanin in their hair, eyes or skin colour -- a condition known as albinism.
Limited genetic variation
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." Brown-eyed individuals, by contrast, have considerable individual variation in the area of their DNA that controls melanin production.
Professor Eiberg and his team examined mitochondrial DNA and compared the eye colour of blue-eyed individuals in countries as diverse as Jordan, Denmark and Turkey. His findings are the latest in a decade of genetic research, which began in 1996, when Professor Eiberg first implicated the OCA2 gene as being responsible for eye colour.
Nature shuffles our genes
The mutation of brown eyes to blue represents neither a positive nor a negative mutation. It is one of several mutations such as hair colour, baldness, freckles and beauty spots, which neither increases nor reduces a human's chance of survival. As Professor Eiberg says, "it simply shows that nature is constantly shuffling the human genome, creating a genetic cocktail of human chromosomes and trying out different changes as it does so."

Story Source:
The above story is based on materials provided by University of CopenhagenNote: Materials may be edited for content and length.

Journal Reference:
  1. Hans Eiberg, Jesper Troelsen, Mette Nielsen, Annemette Mikkelsen, Jonas Mengel-From, Klaus W. Kjaer, Lars Hansen. Blue eye color in humans may be caused by a perfectly associated founder mutation in a regulatory element located within the HERC2 gene inhibiting OCA2 expressionHuman Genetics, 2008; 123 (2): 177 DOI: 10.1007/s00439-007-0460-x

Robert Redford: Republicans are 'living in the 1950s' on the environment,... I'm not so sure Robert..


The Oscar-winner takes aim at Republican senate leader Mitch McConnell, saying he "looks like he just slid out from under a rock".








Robert Redford opens Sundance London on 26 April.
Robert Redford opens Sundance London on 26 April. Photo: GETTY
Robert Redford, the Hollywood star and long-time environmentalist, has accused Republicans of "living in the 1950s" with their approach to their environment. 
The Oscar-winner took particular aim at Mitch McConnell, the Republican leader in the Senate, who has been a champion of the coal industry. 
“He represents the polluters’ interest because he is living in the 1950s," Redford told Variety. He added that the bespectacled 72-year-old senator "looks like he just slid out from under a rock". 
Redford, who is 78, is a regular contributor to America's polarised political debate over the environment but has been especially forthright in his opposition to the construction of the Keystone XL pipeline. 
The controversial pipeline would carry oil from the tar sands of Canada through to refineries on the southern coast of the United States. 
Republicans are wildly enthusiastic about the proposed project, saying it would boost the American economy, while environmentalists like Redford argue it would be a major contributor to climate change. 
Barack Obama, the US president, has spent years on the fence over the issue, refusing to either approve or reject the proposed pipeline until a lengthy state department review is completed. 
Redford deployed an argument often used by American environmentalists: that tar sand oil is particularly toxic and the Keystone project would be of much greater benefit to Canada than the US. 
"We are putting our environment at risk to ship dirty oil, the benefits would go to another country because it is all going to be exported," he said. 
Republicans in Congress are already moving forward with a bill to force the pipeline's immediate approval, which Mr Obama has promised he will veto. 
preliminary state department review found that the construction of the pipeline would support around 42,000 jobs in the US for a two-year period but that once finished, Keystone would only support around 50 jobs. 
The falling price of oil has also led to questions about Keystone's financial viability.

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