Geneticists find an interesting source of Eye Colour

[Halden]

A team of Australian scientists have published a new study in the American Journal of Human Genetics that shows that eye colour is determined by a few letters of the DNA sequence and not Genes. A study of 4000 people demonstrated that a change of one letter in a SNP is all it takes to alter eye colour.

SOURCE

[Zygar]

I find the title of the thread misleading. Most people would assume that you are implying that there is no genetic basis for eye colour. What you are saying is that eye colour is dependant not on an entire gene, but on a very short portion of a gene.

But this is cool stuff! It shows how few changes in a DNA sequence are necessary to create a major variation.

[Gilmar]

The article says genes ARE the source of eye color.

[ponderingturtle]

Originally Posted by Zygar

I find the title of the thread misleading. Most people would assume that you are implying that there is no genetic basis for eye colour. What you are saying is that eye colour is dependant not on an entire gene, but on a very short portion of a gene.

But this is cool stuff! It shows how few changes in a DNA sequence are necessary to create a major variation.

My understanding was that it was not in a gene but in the junk DNA portion around a gene.

Still not particularly well written article to explain what exactly was found.

Anyone here with enough genetic background to interpret?

[Aepervius]

But here is a relevant quote from the article :

Quote:

"When OCA2 is knocked out, there is a loss of pigmentation. The position of these SNPs right at the start of the gene means it is possible we're looking at a change in the regulation of the gene in people with blue eye colour."

Functional change

So these SNPs, at the start of OCA2, probably regulate how much of the pigmentation protein is produced by the gene. People with brown eyes might have a lot of this protein, while people with blue eyes have less.

It seems that the mutation occurs at a specific position of the OCA2 gene, either changing its expression with a variety of degree (from supressing it to letting it fully with some intermediate), or changing its functionality, resulting in the various color.

I do not see anywhere in the article that the cahnge is in unexpressed DNA but maybe I misread....

[Paul C. Anagnostopoulos]

Here we go:

http://dienekes.blogspot.com/2006/11...three-snp.html

It's likely that the SNPs are regulatory and effect expression levels, although it could also be that they result in a protein change.

~~ Paul

[Paul C. Anagnostopoulos]

Halden, would you like me to change the title of this thread?

~~ Paul

[Orangutan]

Originally Posted by ponderingturtle

My understanding was that it was not in a gene but in the junk DNA portion around a gene.
Snip.

I thought I read somewhere that geneticists were regretting the tag of "Junk" DNA as they were the "Junk" stuff actually had more uses that originally discovered.

Edit: maybe it was Wikipedia:
http://en.wikipedia.org/wiki/Junk_dna

[tracer]

Originally Posted by Halden

SOURCE

From the caption to the picture in the link:

Quote:

there are about 2.9 billion base-pairs in the human genome wound into 24 distinct bundles, or chromosomes

We have 24 chromosomes now? Where did the other 22 go?

(And if they meant 24 chromosome pairs, then where did that new 24th pair come from?)

[hgc]

Originally Posted by tracer

(And if they meant 24 chromosome pairs, then where did that new 24th pair come from?)

Just watch for the people with day-glo eyes. They're the 24 pair mutants.

[joobz]

Originally Posted by Paul C. Anagnostopoulos

Halden, would you like me to change the title of this thread?

~~ Paul

No, keep it. I'm think john Hewitt will get a kick out of it.

[athon]

I agree that the title of this thread is not just misleading, it's virtually the opposite of what the paper indicates.

Personally, I think this makes perfect sense in what we know about eye colour. Physiologically, its the placement of pigment in the layers of iris tissue that gives the variation. A small variation in a few base pairs could be all that's necessary to account for this, I guess.

Although I do remember reading somewhere that eye colour relies on something like a matrix of ten different genes. I wonder if this was wrong, or if it still requires a matrix of genes with variation relying on just one.

Athon

[Dark Jaguar]

Originally Posted by Zygar

I find the title of the thread misleading. Most people would assume that you are implying that there is no genetic basis for eye colour. What you are saying is that eye colour is dependant not on an entire gene, but on a very short portion of a gene.

But this is cool stuff! It shows how few changes in a DNA sequence are necessary to create a major variation.

Eye color isn't really major though. Think in terms of programming. In a web page, while adding an entire new feature requires a lot, if you already have a HEX code assigned to determine color, then all it takes is a single bit change in that hex color and you alter the color of the text it modifies.

However, by the same token a massive coded portion can all point to a single "bit" of code, depending on how it's coded, which will either activate or deactivate it completely. It isn't that that single bit codes for that feature, the other massive section does that, it's just that it is dormant until that single bit turns it on. The same could be true with DNA.

[Halden]

Quote:

The study, which focused on twins, their siblings and parents, shows - conclusively - that there is no "gene" for eye colour.

The study concluded that is was a variation in the SNPs near the OCA2 gene that affect the amount of pigment in the eye and therfore it is not the Gene that decides. This is what I meant by the title and I apologize if this has mislead people.

Paul: Go ahead and change the title.

[athon]

Originally Posted by Halden

The study concluded that is was a variation in the SNPs near the OCA2 gene that affect the amount of pigment in the eye and therfore it is not the Gene that decides. This is what I meant by the title and I apologize if this has mislead people.

Paul: Go ahead and change the title.

In that there is no 'blue' and 'green' colour? We've known that for quite some time, though. Even if the precise mutations are novel discoveries.

Athon

[Halden]

Wow, tough crowd.

I guess next time I will have to look for more substantial information.

[athon]

Just have to watch the wording. So many arguments occur around these parts because two people who share similar views have a different understanding of definitions.

Please, don't be offended. Just expect anything you post to be torn apart and put back together again. It's actually quite an educational experience.



Athon

[ponderingturtle]

Originally Posted by Orangutan

I thought I read somewhere that geneticists were regretting the tag of "Junk" DNA as they were the "Junk" stuff actually had more uses that originally discovered.

Edit: maybe it was Wikipedia:
http://en.wikipedia.org/wiki/Junk_dna

Mabey. I just thought we knew the codes to look at and say stuff between code x and code y is a gene. Thus you can say you share 98% of your genes with a chip, but your DNA varies up to 40% from other humans.

Now it is not suprising that not all of the DNA not in genes is useless, but have they removed the idea of concidering a gene to be a select portion of the DNA?

[ponderingturtle]

Originally Posted by Halden

Wow, tough crowd.

I guess next time I will have to look for more substantial information.

Absolutely, it is an unwritten rule to haze the new people here right?

[Paul C. Anagnostopoulos]

Yes, it is, but so far Halden is doing quite well.

~~ Paul

[Halden]

I have no problem with the hard time as it only makes one try harder.

Thanks for the title change paul.

[Molinaro]

My eyes change color with my mood.

They are often brown with streaks of grey.
They are sometimes light green with streaks of grey.
They are sometimes orange.
They are sometimes very dark brown with no streaks.

[Orangutan]

Originally Posted by Molinaro

My eyes change color with my mood.

They are often brown with streaks of grey.
They are sometimes light green with streaks of grey.
They are sometimes orange.
They are sometimes very dark brown with no streaks.

Sorry but I am skeptical (would you expect anything less), Are you sure they don't change with different lighting conditions. My eyes reportedly change from grey to green to blue but it generally reflects what color T-Shirt I am wearing.

Would mood changing eye color qualify as paranormal? You could win a $M!

My eyes change with photo-shop.
Sometimes they are blue,
sometimes green,
Mostly they reflect a screaming aggressive male orangutan.

[Molinaro]

I havn't done any scientific studies.. I just have my girfriend(s)' word to go by.

[ZirconBlue]

Originally Posted by Molinaro

I havn't done any scientific studies.. I just have my girfriend(s)' word to go by.

Notoriously unreliable witnesses, girlfriends.

[Zygar]

Originally Posted by Dark Jaguar

Eye color isn't really major though. Think in terms of programming. In a web page, while adding an entire new feature requires a lot, if you already have a HEX code assigned to determine color, then all it takes is a single bit change in that hex color and you alter the color of the text it modifies.

However, by the same token a massive coded portion can all point to a single "bit" of code, depending on how it's coded, which will either activate or deactivate it completely. It isn't that that single bit codes for that feature, the other massive section does that, it's just that it is dormant until that single bit turns it on. The same could be true with DNA.

Yes, I agree about the dormancy. I am just pointing out how little it takes to make a fairly significant change.

And while eye colour doesn't seem that big, consider that many species of mammals have consistent eye colours across the species. And given how important eye colour is to us humans, I consider that variation to be rather significant.

[articulett]

People used to use eye color as a way of explaining recessive and dominant inheritance, but anyone can see that is an incorrect explanation because there are many variations between light blue eyes and dark brown eyes. The article is saying that eye color depends on how many "working" eye color alleles you have. The more you have, the more pigment that you will see in the eyes--unless you have 2 copies of the gene which causes albinism. Albinism makes it so that the eyes can't translate the genes for color, but they are still present as though the person wasn't an albino and these genes will be expressed in offspring (unless they happen to be an albino also.)

[luchog]

Originally Posted by Orangutan

Sorry but I am skeptical (would you expect anything less), Are you sure they don't change with different lighting conditions. My eyes reportedly change from grey to green to blue but it generally reflects what color T-Shirt I am wearing..

That sounds like a particularly extreme example of colour change, but I've personally witnessed an ex-girlfriend's eye colour change from hazel to a pronounced green with no change in lighting or in anything that could be reflected (such as clothing), or even a change in position. The change occurred at the same time as... certain other physiological changes, in accordance with... certain external stimuli.

I've also noticed relatively minor changes in mine and others that seem to mirror, not mood, but physiological states (health, stress, etc). And being that I, and many of my aquaintances, tend to wear exclusively black clothing the vast majority of the time, it wasn't 'cause of a shirt colour change.

[Modified]

Originally Posted by luchog

That sounds like a particularly extreme example of colour change, but I've personally witnessed an ex-girlfriend's eye colour change from hazel to a pronounced green with no change in lighting or in anything that could be reflected (such as clothing), or even a change in position. The change occurred at the same time as... certain other physiological changes, in accordance with... certain external stimuli.

I've also noticed relatively minor changes in mine and others that seem to mirror, not mood, but physiological states (health, stress, etc). And being that I, and many of my aquaintances, tend to wear exclusively black clothing the vast majority of the time, it wasn't 'cause of a shirt colour change.

What about a change in pupil size affecting the color?

[CapelDodger]

Originally Posted by Molinaro

I havn't done any scientific studies.. I just have my girfriend(s)' word to go by.

Have you considered that the observed colour might change with your girlfriend's mood? In my experience anything's worth considering as a possible clue to a woman's mood, my experience being one of having far too few clues. On occasion, so I've been told, no clue at all.

[CapelDodger]

Originally Posted by Modified

What about a change in pupil size affecting the color?

Oh, I get it now, luchog was talking about drugs.

[CapelDodger]

Originally Posted by Halden

Wow, tough crowd.

I guess next time I will have to look for more substantial information.

I'm sure you'll excuse people - me included - who couldn't immediately distinguish you from the "What about this, eh? Eh? It's science!" numpties who crop up here. Notice how the reaction was softly spoken and tentative but implied the big stick.

To avoid the T'ai Chi effect, always make a meaningful comment or ask a question in an opening post. Or alternatively never start a thread (I don't, I just leech on other people's).

Welcome . And Happy Solstice Everybody!

[CapelDodger]

Originally Posted by Zygar

And while eye colour doesn't seem that big, consider that many species of mammals have consistent eye colours across the species. And given how important eye colour is to us humans, I consider that variation to be rather significant.

How much selection pressure does eye colour exert? Poets might make a big thing of it in recent times but I can't help thinking genetic drift gave them the material to play with. Compared to figure, face and fortune eye-colour is an afterthought. OK, it worked for Steve McQueen, but what proportion of the women he could have impregnated did he actually impregnate? A very small one. I rest my case.

Damn, I love Solstice.

[athon]

Originally Posted by ponderingturtle

Mabey. I just thought we knew the codes to look at and say stuff between code x and code y is a gene. Thus you can say you share 98% of your genes with a chip, but your DNA varies up to 40% from other humans.

Now it is not suprising that not all of the DNA not in genes is useless, but have they removed the idea of concidering a gene to be a select portion of the DNA?

The precise definitions for 'gene' have been argued in recent years. Once, genes were only considered to be codes, and as such, had a particular structure in which the code could interact with particular enzymes in order to be translated. Now we know that there are constructs throughout the genome which act physically in order to assist with genetic expression. Some describe these as genes, even though they don't have the typical structure of one.

Athon

[athon]

Originally Posted by CapelDodger

How much selection pressure does eye colour exert? Poets might make a big thing of it in recent times but I can't help thinking genetic drift gave them the material to play with. Compared to figure, face and fortune eye-colour is an afterthought. OK, it worked for Steve McQueen, but what proportion of the women he could have impregnated did he actually impregnate? A very small one. I rest my case.

Damn, I love Solstice.

It might have a lot to do with reading facial expression. Blue eyes are easier to watch for subtle eye movements than brown eyes are.

Eyebrows are thought to play a role in this; the movements of eyebrows detail emotions better than those who don't have them.

Athon

[ZirconBlue]

Originally Posted by Modified

What about a change in pupil size affecting the color?

For example, many people think that David Bowie has two differently colored eyes, when in fact he just has one pupil that is always dilated.

[Zygar]

Originally Posted by CapelDodger

How much selection pressure does eye colour exert? Poets might make a big thing of it in recent times but I can't help thinking genetic drift gave them the material to play with. Compared to figure, face and fortune eye-colour is an afterthought. OK, it worked for Steve McQueen, but what proportion of the women he could have impregnated did he actually impregnate? A very small one. I rest my case.

Damn, I love Solstice.

I don't remember mentioning selection pressure. Only that we make a big deal over eye colour.

[CapelDodger]

Originally Posted by Zygar

I don't remember mentioning selection pressure. Only that we make a big deal over eye colour.

People make a big deal of mobiles or cars. Poets made eye-colour a thing when they ran out of tit-references. It's not important at a genetic level, which is kinda the scope of this thread.

[articulett]

Actually, the perceived change in eye color is probably an illusion based on clothing and surround colors--
To see how readily your color perception can be altered, check out these illusions:
http://www.johnsadowski.com/big_spanish_castle.php (my favorite)
http://www.planetperplex.com/en/img.php?id=166 (shows how contrast messes with color perception)
http://www.planetperplex.com/en/img.php?id=35
http://www.mindfake.com/illusion_55.html
and this one is a rather rude joke that colorblind people can't get:
http://www.tshirthell.com/store/prod...?productid=559

Although you may notice a persons eyes more as their mood changes and as the pupil dilates and constricts with lighting--it is unlikely that the pigment is actually undergoing any alterations. The more likely explanation is your perception is leading to the illusion that the eyes are changing colors.

[articulett]

I also think that people are unaware of how lighting and such changes color. If you do a color sample of skin or eyes or teeth in photoshop, you get a whole pallet of different colors in a single eye when sampling by pixel. Eyes and teeth and skin look one color--but they are clearly a blend of multiple colors, reflections of light, etc. But our eyes see this blend as "one color".

Skin color and hair color are also inherited similarly to eye color--with the more "working" melanin genes you inherit, the darker skin and hair will be. Red hair is a mutation of the traditional "working" color allele which you can only see if there are not too many "melanin" genes to cover it up. If you have dark hair, you could be carrying the red hair mutation and not know it.