Litnet

Beste FC Boot,

Bron

Ek wil jou heelhartig bedank vir die inligting wat jy op my vraag gedeel het.

Ek het nog altyd vermoed dat die kommentaar wat ek elders oor die onderwerp gelees het, logies is.

In die teel van wedvlugduiwe word die eienskap van die oog as deel van die duif se biologie en uiters bepalend beskou.

In menige Godsdiens word die oog as die venster na die siel (van mens, vis, voel en dier) beskou.

By die mens, word blou oë dus ook as iets besonder in die  genetika bepaal en almal teruggelei na net EEN voorouer met die eienskap!

Ja, die genetika het gewis 'n baie akkurate wetenskap geword.

Persoonlik voel ek dit nie nodig om verder as 10 000 jaar in my etniese erfenis terug te gaan nie.

Kyk ek na al die blou oë om my; van Frank Sinatra tot by Denise Vasi, dan voel ek ons deel 'n besonderse etnisiteit - soveel meer met hulle, wie se bloedgroep O-positief daarby is.

Aangesien jou inligting so leersaam is, spoeg en plak ek dit ook by hierdie bydrae van my:

1. Navorsing- Universiteit van Kopenhagen.

2. ' n Vraag beantwoord deur By Dr. Barry Starr, Stanford University

3. Nog ‘n vraag. Do blue eyes stem from the Black Sea 8,000 years ago? USA today

4. Publikasies http://www.livescience.com/9578-common-ancestor-blue-eyes.htmlOne Common Ancestor Behind Blue Eyes.Google die opskrifte vir fotos.  

3 en 4 is eintlik maar net kommentaar op die navorsing deur die Universiteit van Kopenhagen en dus heelwat herhaling kom voor.Hoop dat dit jou vraag beantwoord.

1.Navorsing
Blue-eyed humans have a single, common ancestor University of Copenhagen Associate Professor, Hans Eiberg Department of Cellular and Molecular Medicine Tel: (+ 45) 353 27829 Information Officer, Sandra Szivos Faculty of Health Sciences Tel: (+45) 353 27069

30 January 2008 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 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.”

 2. ‘n Vraag  en antwoord
Eye Color Is everyone with blue eyes related? How was that trait passed on? -An undergraduate from California August 9, 2013

Surprisingly it does appear that most Europeans with blue eyes are pretty closely related.  Scientists can tell this by looking at their DNA. One piece of evidence is that most blue eyed Europeans share the exact same DNA difference that causes their blue eyes.

 Given that there are lots of ways to get blue eyes, this suggests that the people who share this DNA difference all came from the same original ancestor (or founder).  By studying the DNA in a bit more detail, scientists have concluded that this original blue-eyed ancestor probably lived around 6,000-10,000 years ago.

It is important to note here that not everyone with the same trait is necessarily so closely related.  For example, red haired Europeans get their red hair from a variety of DNA differences.  Not all redheads can trace their history back to an original red haired ancestor.

 Now the fact that blue eyes appeared out of nowhere isn’t that weird…our DNA is much less stable than a lot of people think.  Changes in DNA (or mutations) can and do happen all the time so it isn’t surprising that occasionally one will happen in just the right place to cause blue eyes.

 This probably happened a number of times throughout human history. No the weird part is that the blue eye mutation from that original ancestor took hold and spread through Europe.  Usually this means that the mutation had to have an advantage.  If it didn’t, then like most neutral mutations, it would stay at some low level or disappear entirely. 

But it is obviously still around and going strong. You may have noted that I said that mutations “usually” spread because of an advantage.  The reason I had to add that qualifier is that sometimes a trait spreads in a population for different reasons, often having to do with luck. Imagine a mutation that leads to blue eyes appears in an ancestor. 

The blue eyes freak out everyone in the village so this person is banished to an island along with anyone else that villagers might be weirded out by. Now something happens and everyone in the world is wiped out except the people on the island.  Blue eyes will have gone from very rare to very common.

And as these islanders repopulate the world, blue eyes will stay common.  This kind of thing is more common than you might think and there are many examples of this sort of founder effect. And this isn’t the only way that chance might increase a trait.

  Click here to learn about a few others. While these are possible for other traits, it doesn’t look like this is what is going on for blue eyes.  By looking at the DNA around the blue eye mutation, scientists can see that blue eyes have been strongly selected for.  In other words, they had some sort of advantage. (This is another piece of evidence that blue eyes came from a single common ancestor.)

Now the tricky part is coming up with that advantage.  Scientists have proposed a couple of possibilities (neither proved).  One is that blue eyes are so sexy that they are irresistible.  And the other is that blue eyes themselves aren’t that useful.

 Instead, they are a side effect of something that was—lighter skin. Peacock Feathers and Blue Eyes In nature, individuals with the best traits go on to have more children than those without those traits.  The children who end up with these traits then go on to have more children and so on.  After a while, more people have these traits. 

This is one of the major ways that certain gene versions like blue eyes can spread through a population.  Blue eyed people have more kids and their blue eyed kids have more kids.  As blue eyes spread, so does the gene. Usually when we think about an advantage of a trait, we think about something that makes an individual survive better.

 Maybe lighter skin lets them deal better with weak sunlight or being able to drink milk lets them survive harsh winters better.  But not all advantages are like these. Remember that the key to a trait becoming more common over time is that those with the trait have more kids.

 Being a better survivor is one way to accomplish this.  But so is being sexy. If you are more attractive to the opposite sex, chances are you’ll attract more mates.  This “sexual selection” is the idea behind a peacock’s ridiculous tail feathers.  And may be why blue eyes spread so rapidly.  It may be that the people who spread across Europe thousands of years ago found blue eyes irresistible. 

The blue-eyed Casanovas had lots of partners, many of whom ended up carrying their children (who all had at least one copy of the blue eye color gene).   And blue eyed women always had their pick of potential mates (and often chose the blue-eyed ones).

 This is a fun theory but we really don’t have any proof.  We can’t go back in time and ask these folks if they prefer blue eyed mates to brown eyed ones. If this is why blue eyes spread, we may never have a way of proving it.

 Light Skin Advantage with Bonus Blue Eyes Another possibility is that blue eyes didn’t spread because they had any advantage.  Instead they spread because they were a side effect of something that was an advantage—fair skin.

 When humans first ventured into northern Europe, most were in for a rude shock.  Their dark skin was causing them to develop an awful disease called rickets. Back before fortified milk and vitamin supplements, we got most of our vitamin D from the sun. 

In most parts of the world, sunlight is strong and frequent enough that people can get plenty of it even with dark skin.  In fact, given the dangers of the UV light from the sun, dark skin was actually selected for in these sunny places.

But then a few humans moved to Europe with its short, cold winter days.  They had to cover up to keep warm and the sun was hardly out much anyway.  The end result was that with dark skin, they simply could not get enough sun to get enough vitamin D.

There were a few lucky individuals who had the lighter skin they needed to get their vitamin D way up North.  They did better and had more kids.  Over time, fair skin became very common in northern Europeans. One idea is that blue eyes and fair skin sometimes come from the same piece of DNA. 

If this were the case, then blue eyes would just be a trait that hitchhiked along with the more useful light skin. This is another good theory but so far scientists haven't been able to prove it.  The DNA difference that is the most common cause of blue eyes does make skin lighter but it isn’t the major reason some Europeans have such pale skin. 

So right now we don’t know why blue eyes spread so far and wide across Europe.  We have some good ideas but no proof yet.  And it may remain a mystery for a very long time.
By Dr. Barry Starr, Stanford University 

 3.Nog ‘n vraag.
Do blue eyes stem from the Black Sea 8,000 years ago?  
By Douglas Stanglin, USA TODAY Updated 2012-02-27 2:24 PM CAPTION By AP

The blue eyes that gave Frank Sinatra his nickname, Paul Newman his allure and Cameron Diaz her magnetism apparently stem from a single mutation by a lone individual who lived around the northwestern coast of the Black Sea about 8,000 years ago, according to a new genetic research.

The findings of a team of researchers from Copenhagen University are published in the latest edition of the journal Human Genetics. (READ:  The full study in Human Genetics CAPTION By Anne-Christine Poujoulat/AFP)

 The study analyzed three generations of a large Danish family, as well as five blue-eyed, light-skinned individuals from Turkey and a blue-eyed, dark-skinned person from Jordan. The Daily Mail quotes Hans Eiberg, leader of the team, as saying that a gene called OCA2 does not "make" blue eyes, rather it turns off the mechanism that produces brown melanin pigment.

 "Originally, we all had brown eyes," he says. The research, as would be expected, is dense, but concludes that the mutuations responsible for blue eye color "most likely originate from the neareast area or northwest part of the Black Sea region, where the great agriculture migration to the northern part of Europe took place in the Neolithic periods about 6,000–10,000 years ago."

The study does not try to explain the evolutionary selection at work, but notes that fair skin, normally associated with blue-eyed people, is better able to make Vitamin D in the weak sunlight in northern latitudes. Another theory, which any Hollywood casting director could attest to, has to do with sexual selection.

Here's how the Daily Mail puts it, in decidedly unscientific prose:
 "The theory is that in Europe, where men had to spend weeks at a time out on the hunt, males were in very short supply. In such societies, women who had flaxen locks stood a better chance of standing out and attracting the attention of the few men that would have been available for mating. Even back then, the blue-eyed blonde was not only in demand, but also definitely would have had more fun.
More from USATODAY 27 Feb. 2012

  4.Publikasies
http://www.livescience.com/9578-common-ancestor-blue-eyes.htmlOne Common Ancestor Behind Blue Eyes Jeanna Bryner   |   January 31, 2008 03:34am ET   Reese Witherspoon. Credit: Associated Press

People with blue eyes have a single, common ancestor, according to new research. A team of scientists has tracked down a genetic mutation that leads to blue eyes. The mutation occurred between 6,000 and 10,000 years ago. Before then, there were no blue eyes. "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. "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," Eiberg said.

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 Eiberg and his team examined DNA from mitochondria, the cells' energy-making structures, of blue-eyed individuals in countries including Jordan, Denmark and Turkey.

This genetic material comes from females, so it can trace maternal lineages. 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 The mutation is what regulates the OCA2 switch for melanin production. And depending on the amount of melanin in the iris, a person can end up with eye color ranging from brown to green. Brown-eyed individuals have considerable individual variation in the area of their DNA that controls melanin production.

But they found that blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes.  "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." 30 January 2008

(einde van aanhaling)

Dankie FC.

Verskoon my verwaandheid, maar het jy dalk ook soortgelyke inligting oor die genetiese oorsprong van bloedgroepe by die mens?

Namaste!

Blouoog  groete,
Cornelius Henn