What Causes Brown Eyes To Turn Blue?
- Pieter Maas
Genetic mutation makes those brown eyes blue People with blue eyes have a single, common ancestor, according to new research. A team of scientists has tracked down a mutation that leads to blue eyes. The mutation occurred between 6,000 and 10,000 years ago, so 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 affected the so-called OCA2 gene, which is involved in the production of, 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, 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.” : Genetic mutation makes those brown eyes blue
What is the rarest natural eye color?
Green Eyes – Green is considered by some to be the actual rarest eye color in the world, though others would say it’s been dethroned by red, violet, and grey eyes. Green eyes don’t possess a lot of melanin, which creates a Rayleigh scattering effect: Light gets reflected and scattered by the eyes instead of absorbed by pigment. This effect makes the eyes look green, but they don’t actually have green pigmentation.
Can brown eyes turn into blue eyes?
A California-based company has developed a procedure that can change brown eyes to blue in a matter of 20 seconds. Stroma Medical created the procedure, which uses a laser to rid your eyes of the dark melanin that makes them brown. This turns them blue.
What is the prettiest natural eye color?
Hazel is the most attractive eye colour in females – Among women, the results were somewhat less defined. While hazel was the most popular eye colour to receive a “like”, it only beat purple eyes – which aren’t naturally possible – by a single match. Only green eyes seemed to suffer at all, with only 11% of matches reached.
|Eye Colour||Total Matches||Female – %|
Can your baby have blue eyes if both parents don t?
Making Eye Color Predictions with Basic Genetics – If you want to try and predict your baby’s eye color, pull out your high school biology textbook to help narrow down just how likely it is that your baby will have blue eyes. If you didn’t keep it, don’t worry, I’ll give you a quick review.
- As FamilyEducation’s Genetics Expert, I have developed my knowledge on these topics through a combination of college classes, teaching, and self-study.
- We all inherit two copies of each gene (allele), eye color included.
- One copy comes from our mother, and one from our father.
- Both alleles are stored in our chromosomes (our genetic code) and can be passed on to our children, but only one presents in how we look.
Dominant genes present while recessive genes “hide out” in the DNA code for a chance to pass on to future generations. Generally, darker colors are the dominant traits, while lighter colors are recessive, so a person with one brown-eyed gene and one blue-eyed gene will have brown eyes.
Blue eyes + blue eyes = 100% chance of blue eyes Brown eyes + blue eyes = 50% chance of blue eyes, but only if the brown-eyed parent carries a blue-eyed gene. If not, the chance is 0% Brown eyes + brown eyes = 25%, but only if both parents carry the blue-eyed gene. If not, the chance is 0%
It is important to remember that this theory is a simplified version of what really happens at the genetic level. Human eye coloring is actually controlled by a complex genetic process and there are many different eye colors other than just blue eyes and brown eyes.