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Audacity of Truth
The eyes have it
Via the BBC:
Scientists have made a breakthrough in their understanding of the genetics behind human eye colour.
They found that just a few “letters” out of the six billion that make up the genetic code are responsible for most of the variation in human eye colour.
The research, by a team of scientists from Queensland, Australia, will appear in a forthcoming issue of the American Journal of Human Genetics.
The findings are based on a genetic study of nearly 4,000 individuals.
Differences in eye colour are largely down to “single nucleotide polymorphisms” (SNPs – pronounced “snips”); variations in the sequence of letters that make up a single strand of human DNA.
SNPs represent a change of just one letter in the genetic sequence. These changes, or mutations, in our DNA can have important consequences for how the gene gets physically expressed.
All the SNPs are located near a gene called OCA2. This gene produces a protein that helps give hair, skin and eyes their colour. And mutations in OCA2 cause the most common type of albinism.
Brown and blue
The study, which focused on twins, their siblings and parents, shows – conclusively – that there is no “gene” for eye colour.
Does this mean ’so long’ to the long-held belief that recessive genes were responsible for the color of your eyes?
Hat tip to Kim Priestap, who posted a picture of one of her eyes as the opener to her blog post about this. Here are some eye pix of my mom, sis, and me:
ST’s eldest sis
ST’s middle sis
ST
ST’s mom (I had to blow the pic up a bit, but hopefully the hazel-green of her eyes shines through – it does to me 
)
And these scientists are saying that there is no gene for eye color? C’mon!
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13 Responses to “The eyes have it”
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Disclaimer: The views expressed on this blog do not necessarily reflect those of ST's advertisers, nor do their opinions necessarily reflect ST's. Stats
/Sigh I could stare into your eyes forever.
– Lorica
Mine are hazel…
If the study’s right – I should quit giving my wife a hard time about our blue-eyed baby (I’m brown and she’s hazelish [HS Biology says I should win])
Mine are hazel, too. And right now they could be staring deep into Sis’ eyes!
LOL
(Prepare to be bored with a lot of non-essential scientific mumbo-jumbo.)
I think their “there is no gene for eye color” is a little misleading, because it implies that therefore eye color is not hereditary. Specifically, the gene is for the regulation of a protein which causes the eyes to take on a certain color. More protein means browner eyes, less means bluer. The varying amounts of protein account for the wide variation in eye color. And a variation in way the protein is made causes the eyes to be green instead of brown.
So now, instead of saying that people inherit brown eyes or blue eyes, we will be more accurate in saying that people inherit protein production.
color: Blue………………..Brown
protein: Little………………Lots
(I’m ignoring the brown/green difference for the sake of argument.)
So now instead of saying “I have the gene for blue eyes” or “I have the gene for brown eyes,” we should say “I have the a that produces little of that protein” or “I have the a that produces a lot of that protein,” respectively. Which boils down to the same thing, essentially. The difference is that instead of just brown/blue, there’s a lot of in-between.
And to clarify, that’s “a lot of in-between” when you’re looking at a cross-section of the population. When you’re looking at one individual, that person has only two copies of the gene–ones he got from his mother and father.
High-school genetics was pretty straightforward. Mom and dad had either blue or brown eyes. Brown was dominant, blue was recessive, so if brown and blue were present together (a hybrid), the eyes would be brown. So, two parents with blue eyes would have children all of which would have blue eyes, because no dominant brown gene was present. If one parent had brown eyes and the other had blue, children would have brown eyes or blue based upon whether or not the brown-eyed parent was a hybrid. And two parents with brown eyes could have blue-eyed children if they were both hybrids (B=brown gene, b=blue gene):
Mom………B…………………….b
Dad…B….BB (brown)…….Bb (brown)
……….b….bB (brown)…….bb (blue)
This simple way of thinking about genes meant that two blue-eyed parents would never have a brown-eyed child, although in fact, this does happen, tho it’s very rare (and up until now, thought to be due to mutation [or the milkman]). And of course, it said nothing about the variation of eyecolor among siblings.
But the new way of looking at eye color provides a system that answers many of these questions much better.
Let’s say that X100 makes tons of the protein, and X1 makes only a little bit. And let’s say that at a combined total of X50 or more, eyes take on a more brownish hue than blue. You get a gene from your mom and a gene from your dad; add the amount of protein the genes produce together, and if you produce more than X50, you’ll have brown eyes.
So let’s see some examples to get an idea of how it works:
Mom has blue eyes (X14+X19 from her parents for a total of X033)
Dad has brown eyes (X54+X68 from his parents, for a total of X122) (Note that in the “old system,” dad would be a pure-bred, because each of his genes individually put him over the brown level)
Mom…………..X14…….X19
Dad…X54…..X68…….X73
………X68……X82…….X87
So all of their children will have brown eyes.
Mom has brown eyes (X84+X15 from her parents for a total of X099) (Note that in the “old system,” mom would be a hybrid, because only one of her genes would put her over the brown level)
Dad has blue eyes (X13+X13 from his parents, for a total of X026)
Mom…………..X84…….X15
Dad…X13…..X97…….X28
………X13……X97…….X28
Half of their children will have brown eyes, and half blue.
This system also explains how two blue-eyed parents can have a brown-eyed child:
Mom has blue eyes (X14+X25 from her parents for a total of X039)
Dad has blue eyes (X26+X11 from his parents, for a total of X037)
Mom…………..X14…….X25
Dad…X26…..X40…….X51
………X11……X25…….X36
One quarter of their children will have brown eyes.
The above information (for example, the statement that X50 and above would have brown eyes) is just a guess on how it works based on the article and other information, but I think it’s a fairly accurate basis.
I hope there are some people still awake
all three sistas have the same eyes…..
Yax …. uh, I’ll take your word for it
I wish you wouldn’t post pictures like that, now I’m going to be distracted all day.
You mean there are three Sister Toldjahs?
Isn’t it Sisters Toldjah??
I have to admit there is something sultry about the whole eye only photos of the Sisters. 
– Lorica
ST, all y’all got me wishing I were 20 to 30 years younger and single.
Hell, PCD, I’m wishing I was 20 to 30 years younger, and there were three of me!
Oh, and that I was less of a doofus, or rather less repulsive to wimmen.
Thanks for the Christmas present – That pic was the best one I’ve gotten.
Amazing how fast the science goes down the drain when a man starts to stare into a beautiful womans eyes.
– Lorica