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All those with blue eyes have a common father

The range of colors in the eyes from brown to green can be explained by differences in the amount of melanin in the iris, but in those with 'pure' blue eyes, there is a more limited range of melanin in the eyes. It turns out that the genetic diversity within them is different, which allowed scientists to trace them back to the common ancestor who lived 6-10 thousand years ago

A blue eye and a green eye. The differences between the photos are not only in the tone but also in the genome. From Wikipedia
A blue eye and a green eye. The differences between the photos are not only in the tone but also in the genome. From Wikipedia

The range of colors in the eyes from brown to green can be explained by differences in the amount of melanin in the iris, but in those with 'pure' blue eyes, there is a more limited range of melanin in the eyes.

New research reveals that people with blue eyes have a common ancestor. A team of scientists from the University of Copenhagen traced the genetic mutation that occurred 6,000-10,000 years ago and is (and is) responsible for blue-eyed humans living on Earth today.
What is the genetic mutation?
"Originally all humans had brown eyes," says Prof. Hans Iberg from the Department of Cellular and Molecular Medicine at the University of Copenhagen. "However, a genetic mutation affected the OCA2 gene in our chromosomes and the result was turning off the ability to develop brown eyes.
OCA2 (is a gene that) encodes the P protein involved in melanin production. It is the pigment that gives the color to hair, eyes and skin. This change that occurred in the gene related to OCA2 does not turn off the gene completely, but rather limits its actions to reduce the ability to produce melanin in the iris - thus it "dilutes" brown eyes and turns them blue. This conversion effect of OCA2 is specific (targeted). If the OCA2 gene was completely destroyed in the shutdown process, those people would not have melanin in their hair, eyes or skin, a phenomenon known as "albinism".

limit genetic variation
Variation in eye color from brown to green can be explained by variation in the amount of melanin in the iris, but individuals with blue eyes have a low degree of variation in the amount of melanin in their eyes. "From this we can conclude that all blue-eyed humans originate from a common ancestor." says Prof. Iberg. "Everyone inherited the same switch off at the same point in their DNA. Unlike them, people with brown eyes are very diverse in the amount of melanin in the area of ​​the DNA that controls melanin production.
Prof. Iberg and his team tested mitochondrial DNA and compared the eye color of people with blue eyes in countries with different characteristics - Jordan, Turkey and Denmark. These findings are the latest in a decade of genetic research that began in 1996 when Prof. Iberg discovered that the OCA2 gene is responsible for eye color.

Nature shuffles our genes

The mutation that caused the brown eyes to turn blue is not a positive mutation but not a negative one either. It is one of several mutations such as hair color, baldness, freckles and birthmarks that do not increase or decrease a person's chances of survival. As Prof. Iberg says: "This shows that nature is constantly shuffling the human genome, creating a cocktail of human chromosomes while revealing the changes as it does so."

 

to the notice of the researchers

 

12 תגובות

  1. Speaking of a common ancestor - all humans (regardless of their eye color) living today are descendants of a common ancestor who lived in Africa about sixty thousand years ago (and he was of course black-skinned).

  2. Eye color has an effect on the sensitivity to sunlight, therefore the statement that there is no effect on human survival is inaccurate.

  3. An important caveat - if 6,000-10,000 years ago the mutation was created for the first time, and today it is very common in many human populations - it is likely to have an adaptive value (that is, positive). Such an increase is unlikely to be explained by population culture, genetic drift, bottlenecks and other vegetables.
    It is much more likely that those with blue eyes have an advantage in mate selection.

  4. Blue irises have no evolutionary advantage? Of course they have. It is not randomly distributed... you won't find people with blue irises in Africa (originally) and the opposite is true for Scandinavian countries. In northern latitudes there is little sun and dark irises affect the amount of light entering the eye (some light enters through the iris too). On the other hand, blue irises will allow too much light into the eye in Africa + the chance for cancer will increase. Even nowadays the prevalence of eye melanoma in people with blue irises is much higher

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