Sunday, December 02, 2007

I may be a mutant!

Actually, I already know I'm a mutant, but I may be a mutant twice over.

My blog readers are the coolest people ever. Neek (who appears to be, sadly, blogless) dropped me a note about the concept of 'tetrachromacy', or having super-duper color vision due to a genetic mutation that leads to four (instead of three) types of cones in the retina. I've spent the morning reading up on it, going "hey, I do that" when they describe the behavior of tetrachromats. Mostly it involves things like color memory, seeing variations in color no one else does, and stuff like that. (One description involves an interior decorator who can see differences in paint chips that none of her clients do.)

Wikipedia has a decent basic article on it, here.

There is a better, yet basic, article here, that describes things better in terms of the human implications. It also has a link to the Ishihara color blindness tests, which can be fun to play with.

There is also an article, here, that goes into gory details on the genetics involved (WARNING: it is a PDF file). I tracked on about 75% of the details; I'm not a geneticist, and what little formal study I have in genetics involved plants (didja know ferns can have up to four hundred-odd chromasomes?) and not humans, which is more confusing than you'd first think.

Anyway, the basic gist is, women (only women, it's a double X chromasome deal, related to why men are color blind, basically the gene that controls that stuff is very prone to mutation and variation) can have FOUR types of color receptors in the retina, instead of the usual three. It's estimated that with three color receptors an average person can see about a million colors; with a fourth cone type, that number of visible colors would go up to a hundred million. At least theoretically. Seems that the color sensitivity of the cones is variable, though, even among 'normal' folks, so you get more a graduation of color sensitivity among people. So it's likely that even with the fourth cone, there would be a variation among individuals, as to how sensitive to color they are.

What's REALLY interesting to me is, the great debate these days in the medical community isn't about whether or not the fourth cone mutation happens; it's whether or not the human brain can adapt to it enough to make use of it. Considering I've seen case studies of a kid who had AN ENTIRE HALF OF HER BRAIN REMOVED (because of really bad Epilepsy) and WALKED OUT OF THE HOSPITAL a couple weeks after the surgery, I've got faith the human brain can adapt enough to make use of an extra cone in the retina. Particularly if it's an otherwise functional brain, which is usually the case these days.

I'm going to try to contact a couple of these guys who are doing studies, and see if there's some kind of color test I can take, to verify it. (There's also a genetic test, which I'm game for, but I imagine having me look at some color cards would be a lot cheaper.) I'm quite curious, now.

...I've been reading the behavior of known tetrachromats to the Husbeast, and he's laughing and saying "Oh yeah, that's you."

Oh, my other mutation? I was born without wisdom teeth. Don't have any, never did. I in no way think the genetic code dictating how my teeth come in is related to the genetic code that dictates how I see color is related. But it establishes my genetic weirdness, for sure.


Roxie said...

What a delightful mutation. wonder if the Goober has inherited it. thanks for all the links. I think I may be an alien, but maybe I'm a mutant, too.

Anonymous said...

no wisdom teeth? LUCKY, LUCKY, LUCKY you!

i had to have all 4 of mine pulled at 18 because of pressure they were putting on other teeth. one had to be broken to be removed. a whole lot of no fun. now my daughter (25) is looking at the same kind of fun only maybe without the break-a-tooth part.

as for the color vision, cool, kinda makes sense it would be genetic in terms of a 4th kind of receptor.

i'd mentally been comparing it to being able to hear higher and lower tones than most people. about 20 yrs ago, i drove the computer techs at work nuts by complaining about the high-pitched noise coming from my crt. being men, they couldn't hear it. they finally figured out it was the carrier tone -- somewhere above 17k hz (right abbreviation?) anyway, up where only dogs were supposed to be able to hear it.

i'd thought maybe you were more sensitive to the infra and ultra tones within subtle color mixtures. (like, how the hell do they do day-glo, anyway?)

as for the hemispherectomy, i also remember reading about an autopsy report on a fairly young man. the pathologist, attempting to console the family, had said something to the effect that the deceased probably hadn't had much quality of life, given that his brain had several large vacant areas (cysts? atrophied spots?). the family was quite upset by the doc's words, because the young man had been regarded as a genius.

the off-topic or tangential portions of your blog, incidentally, are a main reason i read it. i have to gigglesnort when someone assumes that knitters are all sweet but not-very-bright old ladies.

for instance, my small knitting group's members include a man who runs a web design company, a woman who teaches college math, a woman with a neurobiology degree from yale, a woman with a music degree, a retired woman who does tax accounting and has been a chef/caterer and history teacher, a multilingual student who is completing college in 2.5 years while designing and selling knitted items, and a gourd artist who attracts students from all over. (and then there's me -- a longtime newspaper copy editor. no advanced degrees, but a smattering of knowledge about a multitude of things.)

so, yes, knitting CAN be done by small children and people of limited intelligence, but my guess is that most people who knit these days are pretty bright.

ellen in indy

AnneMarie from PA said...

I wonder if the mutation can occur in only one eye? I have pretty amazing color memory (which drives my husband nuts) and am pretty acutely sensitive to color differentces-- for example, I was one of the ones that looked at your floss/yarn combo and said, "oh my, those don't go together at all!" But I have noticed that one of my eyes (the non-dominant eye) "sees" everything with a slight yellow hue. I think of it as a yellow film, or gel (like in photography) over it. I hate it. It drives me nuts. And I can tell when it's affecting my vision.

By the way, I should add to the discussion that I'm a diagnostic medical sonographer, and when I applied for one of the best programs in the country oh-so-many-years-ago, one of the things the head of the program informally tested us on was the ability to distinguish between very, very slight variations in greys. It turns out that some people just can't distinguish well among fine variations in gray-scale, and so make really lousy sonographers (i.e., miss potentially dangerous stuff). I still manage once in a while to see stuff, film it, bring it in to the radiologist, and he or she can't see what I'm pointing out. Only once did the involved rad go with his own, negative reading over mine. The surgeon who ordered the exam, however, went with my reading-- guess who was right?

Rose Red said...

Interesting - I don't have wisdom teeth either (for which I am eternally grateful, based on other people's stories of having them removed!)

Neek said...

Thought you'd get a kick out of reading about it, I stumbled across that article a few months ago and thought it was super cool (because I'm a nerd like that). Fortunately or unfortunately I seem to be blessed with normal trichromat vision, can't even begin to imagine what you can see :)

p.s. I'm a regular lurker and sadly I don't have a blog, I think I've added you as a friend on ravelry though (username is neekie)

Amy Lane said...


Okay--when I was 18, my dad got me a crappy, 1970 Datsun (it was 1985) that I called, for as long as I had it, light blue.

Everyone else called it white. For YEARS my family has said I was crazy...C.R.A.Z.Y. because that car was OBVIOUSLY white.


*ahem* If you will excuse me, I have to dance around in my kitchen, pumping my fists and screaming...

Becka - The Knitting Wounded said...

Having no wisdom teeth is awesome, the wave of the future I think. I have extra teeth, which, in the wild, would totally put me out of the mood for procreation. I miss Darwin sometimes...

Louiz said...

I have no wisdom teeth, nor does my brother. My sister had hers extracted and me and my brother are really pleased we lucked out! Will check out the links later, but I suspect (given that I couldn't tell the difference in greens) that I'm as close to normal as I'll ever get!

Leanne said...

I wanna be a mutant too. Waaaaahhhh. I think my colour perception is likely normal, although I could see a difference in those greens you showed yesterday.

I did only have 3 wisdom teeth. Does that at least make me a quarter-mutant?

Louiz said...

Oh, and need to add (after reading the articles) Himself sees no difference in colours. He sees colours but not shades/variations. This blue is the same as that blue. This green is the same as that green. Must ask him about blue/green colours and how he sees them. He doesn't like yellow though if that is significant. Dont think he has colour deficiency as such but he only sees one shade of a colour, which confuses me (and I no longer take him with to help pick matching colours).

Alwen said...

Like Leanne, I only have three wisdom teeth.

Missing one or more wisdom teeth is a fairly common trait -- something like 20% of people are missing wisdom teeth, about the incidence of color blindness.

I have two color-blind brothers out of three, & concentrated on genetics in college. Mostly plant, but you had to take the basic gen. class to get into the higher ones.

The new human genome stuff coming out is just fascinating. Some of the missing-tooth stuff is developmental (non-inheritable), and some of the mutations that cause missing teeth are pretty major and have negative effects on other organs. They are just starting to pick out the genes like PAX9 that result in teeth failing to develop.

Another thing we see in women is that we get two X chromosomes, right? However, at a certain point in development, if all goes well, one X gets switched off in each cell. That means even though I have two, usually in each cell only one is expressed. And this is random, so some cells use the paternal X, some use the maternal.

[looks around at glazing eyes]

Oh. Uh. Sorry. Genetics, color vision, and that. Fascinating stuff. I'll shut up now.

NeedleTart said...

How wonderful that we have our blog connections to make us mutants.....Wait, that didn't come out right....
I know where your wisdom teeth are. Younger Son and his Girlfriend both had 6. Just comtemplate that gene match for a while....

Caroline said...

I think I'm going to have the opposite problem from needletart's family. I seem to only have 3 wisdom teeth (who knows, maybe the fourth is just a late bloomer? ;), and my fiancé lacks permanent teeth in a few places...

Oh, how I love genetics! And tortoise-shell cats, because they make me think of genetics. :D