www.whyville.net Sep 22, 2014 Weekly Issue

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The Trouble With Colors

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Author's Note: The name of the biology teacher interviewed has been changed, but he is indeed a biology teacher.

When average humans, or trichromats, look at the colors red and green, they can see a distinct difference. A dichromat, on the other hand, has trouble differentiating the two. This is because while a trichromat has three cones, or light-receptive cells, in his retina, one is an unresponsive mutant one. A tetrachromat has three average working ones plus a responsive mutant one.

On Newcastle University's section of their website dedicated to tetrachromacy, they ask if sometimes it's hard to find matching outfits, or perhaps that you notice other peoples' clothes don't quite match. They do, however, indicate that tetrachromacy would give you a wonderful memory for colors. So is tetrachromacy a blessing, or a curse?

"Research seems to say we don't know ... tetrachromats don't know how trichromats see, and trichromats don't know how tetrachromats see . . . so it is hard to determine if it would be a positive or a negative. However, it seems like it would offer a greater intensity of colors, allowing for more intense color vision, which seems like it would be a good thing," said biology teacher Mr. X.

Tetrachromacy is limited to women only. This is because men have only one x-chromosome, while women have two. Because men only have one, if something goes wrong in the M or L-opsin copy in his genes, he could be considered colorblind as he cannot inactivate this chromosome like a woman. Women have two x-chromosomes so their bodies often deactivate one of them because they don't need twice the amount of those proteins that men do, and it doesn't matter whether they deactivate the maternal or the paternal one.

"With tetrachromacy, individuals would have a more sensitive color vision and higher sensitivity to more colors, so in that way, to be tetrachromatic would seemingly give you a better grasp of colors," said Mr. X.

Tetrachromacy is highly rare because most potential tetrachromats don't utilize their mutant cone. The mutant cone most times is unresponsive so although they possess the extra cone, it does not hold the skill to work properly. When a woman's mutant cone, however, is fully perceptive, she sees 100x more colors than the average human. One woman who was studied for her tetrachromacy said she saw ten colors in the average rainbow, rather than the usual seven.

Which leads us to the question: which has it harder, dichromats or tetrachromats?

"Being unable to see colors would be far more difficult than seeing more colors . . . in my opinion," explained Mr. X.

Only about 12% of women have the four opsins, and even fewer have the ability to put them to use. Newcastle University has a research team dedicated to tetrachromacy, researching on almost any willing individual in their area that claims to have the condition. However, upon getting news that an individual will travel to Newcastle to do the tests, the team still acknowledges the request.

"Even as a potentially positive mutation, humans aren't really bound by the general 'natural selection' rules that we find in the natural world though, so it's frequency in our population won't be determined by [its rarity]," said Mr. X.

To be sure that a woman could be a potential tetrachromat, the researchers ask them about the vision of some of their male relatives. A woman is much more likely to be a tetrachromat if one of her male relatives are colorblind or have color deficiency, because in this case, the mutated chromosome would be passed along to the female or passed from the female to her son.

The Newcastle research team also gave a link to the X-Rite color test, saying that they cited it as a resource for males to figure out if they have some sort of vision deficiency. The test begins with four strips of colors starting with one shade, and ending in another. The shades in between the two colors are randomized and one is asked to put them in order, gradually going from the first shade to the second. After this is done, one must click a button so that their test is graded.

The results of the test are then given, and the participants are asked to give the website their age and gender to check how well they did. The scale goes from 0, meaning perfect color acuity, to 99, which means low color acuity.

If the male relative tested is given the results saying that he may have a color deficiency, it's advised that the female attempting to find information about her potential tetrachromacy should send the results to the research team at Newcastle. Tetrachromacy could shed light on parts of the color spectrum previously thought invisible to the human eye.

Author's Note: Sources: http://www.xrite.com/online-color-test-challenge
An art teacher very interested in color!


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