The physical appearance of humans has many variances from height and hair color to shape and skin color. These are traits that all have a genetic basis in our DNA. our genes determine how these traits will appear in each one of us. The human eye can come in colors such as blue, green, and many variations of brown. This variation of color comes from the amount of melanin in the eye, much like hair and skin color is controlled by melanin. New research has shown that all those with blue eyes have a common ancestor. They have done this by tracking down a genetic mutation. The genetic mutation is estimated to have occurred between 6,000 and 10,000 years ago.
Variation in eye color is very common. From brown to green, there is a large amount of individual variation in eye color. The variation in green and brown eyes is explained by the differences in melanin in the iris. Green and brown eyes have large amounts of variation in the iris, but blue eyes do not. Blue eyes have a very low amount of variation of melanin in the iris. This little variation in all blue eyes led to the conclusion that all blue eyes are linked to the same ancestor. All those with blue eyes have blue eyes because of the same change in the same spot in their DNA.
All humans originally had brown eyes. The blue eye gene came from a mutation of the DNA in the OCA2 gene. The OCA2 gene is a gene that codes for the P-protein. The P-protein is a protein involved in the production of melanin. The melanin produced is what is responsible for giving not only our eyes color, but also our hair and skin. The mutation does not affect the gene completely. The gene is not completely shut off or else the hair and skin color would also be affected. The mutation only reduces the production of melanin in the iris. Without the production of melanin in the iris, it appears as blue rather than brown.
This study was done on individuals with blue eyes from places all over the globe. Places as diverse as Turkey, Denmark, and Jordan. The gene for all of these blue eyed individuals was the same. Blue eyes is a mutation in the genome that was neither a positive mutation nor negative mutation. It was a passive mutation that has allowed for both brown and blue eyes to last through time.
I don't know why it didn't occur to me that blue eyes must have originated in some common ancestor. Looking at this human trait I have always felt like there must be more too it than just a lack a melanin. I wonder if it is possible for purple eyes to exist (like those in the Targaryen bloodline in the Game of Thrones books). Would purple eyes also have a lack of melanin or would there be something more that allowed this supposed trait to exist?ReplyDelete
A Targaryen eye trait could be possible through some new mutation that is a gain of function mutation, but that would be very rare. The blue color comes from lack of melanin, and green eyes from moderate melanin, and brown from more melanin. This would require a new form of melanin with a purple pigment.Delete
Posted by John Mariano
Eye color has always fascinated me and its crazy how involved the genetics behind it is. In my family, my mom has brown eyes while my dad has green eyes and me and my two siblings all have different colored eyes. I have green, one brother has blue, and the other has brown eyes. Both of my parents have to be carrying a recessive gene for eye color because one brother has blue eyes. It is also interesting how a single mutation can lead to such crazy variation in eye color in the world population and how different eye colors are dominant in certain parts of the world. I wonder if any new mutations will occur in the future that will lead to even crazier eye colors, like red.ReplyDelete
The more I think about the findings the more it makes sense to me and more questions arise. I wonder if it has something to do with the general evolutionary history of humans. When skin and hair color changed due to change exposer to UV, did it also effect eye color or was that an independent mutation? And is blue the default color or can be there something different? As far as I understood the article, the eyes are blue because of lack of melanin. So I guess no crazy color for us...ReplyDelete
Blue eyes is the result of the mutation which causes very little melanin in the iris. I am not sure if there would be any color change for a mutation that caused no melanin in the eye (It probably would not good for thew though). I think in order for humans to get a crazy color there would have to be a mutation in the genome at the melanin protein. This mutation would have to change the pigment of the melanin.Delete
Posted by John Mariano
The fact that all people with blue eyes have a mutation in the OCA2 gene and can all be traced back to a single common ancestor with blue eyes is captivating. Most of my family has blue eyes but I never knew that this was caused by a mutated form of the OCA2 gene which we all share! As you mentioned this mutation does not affect survival at all and thus this allele was governed exclusively by genetic drift and random gene flow. The ability to see someone with blue eyes almost anywhere in the world shows how these non-survival based alleles can increase in frequency just by random chance alone. Since blue eyes are fairly common across the world today, I wonder if we have any other features that arose in a way similar to how blue eyes arose. In other words, what other features of modern humanity can be attributed to a non-survival based mutation which arose in a single common ancestor thousands of years ago.ReplyDelete
Posted by James Levangie
I love genetics. It is one of the things about biology that I'm fascinated with. I have always heard that people with blue eyes were all descended from the same ancestor however, i always thought this was a myth. But it makes sense that everyone with this gene would have to come from the same ancestor. I would love to see a phylogenetic tree on the evolution of eye color. I think it would be really cool to compare the differences in this trait.ReplyDelete
I remember being little and wanting to have blue eyes, like my grandfather did, instead of having brown eyes that only showed their real color when the light would hit them. I always thought that blue and green eyes were a result of lack of melanin in the iris, now I find it so fascinating to know that it is actually due to a genetic mutation in the OCA2 gene and the share of one common ancestor.ReplyDelete
This was really interesting to read. I remember learning a bit about this in evolution. I always wondered how a recessive mutation ended up becoming so prevalent around the globe; before humans traveled as easily and frequently as they do today. There is a surgery that removes the brown layer of the iris to reveal a blue color underneath, though I'm not sure how safe it is. People with naturally blue eyes are more prone to light sensitivity issues, so I don't know if side effects like these carry over.ReplyDelete
Posted by Meagan Gustafson
I was diagnosed of herpes virus, I have tried all possible means to get cure but all my effort proved abortive, until a friend of mine introduced me to a herbal doctor called Chief Dr Lucky, who prepare herbal medicine to cure all kind of diseases including herpes virus (Herpes), when i contacted this herbal doctor via email, he sent me herpes virus herbal medicine via courier service, when i received the herbal medicine he gave me step by step instructions on how to apply it, when i applied it as instructed i was totally cured from the virus within 3 weeks of usage. Contact this great herbal doctor today to get your cure.ReplyDelete
Via Email : firstname.lastname@example.org
Whats App : +2348132777335
website : http://chiefdrluckysolutionhome.website2.me/