5 ms·

Why would only women be capable of tetrachromacy? I am a man, but if the test is made public, I would be interested in testing myself. I am not color blind acc

by ryao 10y ago

Why would only women be capable of tetrachromacy? I am a man, but if the test is made public, I would be interested in testing myself. I am not color blind according to color blindness tests, but there have been instances where I disagreed on the color something was with others and while I could consistently use the name that they used for it, I felt it really ought to have been named something else. One involves "green" status LEDs on electronics, which seem more in common with yellow than green to me. They look different from yellow, but they seem closer to yellow than green to me and for lack of a better word, I would rather call them yellow. If I could use a different name for the color, mapping it to green when interacting with others would seem less weird. Another involved the paint of a house when I was young, whose color seemed to poorly resemble what my parents said it was when it was dark. The house has since been repainted. Having three primary colors never made much sense to me either, but that could just be my own ignorance. Anyway, I am sure that there are many more variations in human vision than we realize. The dress incident brought that to light: https://en.m.wikipedia.org/wiki/The_dress_(viral_phenomenon) https://en.m.wikipedia.org/wiki/The_dress_(viral_phenomenon) It would be nice to have ways of categorizing them.

rarec 10y ago
http://news.nationalgeographic.com/news/2012/09/120907-men-women-see-differently-science-health-vision-sex/ http://news.nationalgeographic.com/news/2012/09/120907-men-w... Men and women seeing slightly differently is in line with our biology. Just how it is, really. Men are more prone to color blindness too. https://nei.nih.gov/health/color_blindness/facts_about https://nei.nih.gov/health/color_blindness/facts_about
- ryao 10y ago
  That explains the LED thing. Thanks.
ChuckMcM 10y ago
Simplified version: X chromosome can express 1 or 2 color receptors, Y only expresses 1. Women (XX) can get up to 4, but the X occasionally only produces 1, since women have two X they mostly have 3, sometimes 4 and very very rarely only get 2 (both X only express only one) Men (XY) can get 3 but when the X chromosome only gives 1 they only have 2 and are color blind. Depending on which one they didn't get, that determines their color blindness. [1] http://www.radiolab.org/story/211193-perfect-yellow/ http://www.radiolab.org/story/211193-perfect-yellow/
- maxerickson 10y ago
  https://en.wikipedia.org/wiki/XY_sex-determination_system https://en.wikipedia.org/wiki/XY_sex-determination_system is a useful start for anyone not familiar with the very strong link between some genes and sex determination. The next step from there is that in humans the X chromosome carries more genes than the Y chromosome. Since women have two X chromosomes, they can express multiple variations of genes located there. Men will only possess one variation. This is the reason that color blindness is so much more common in men, some of the genes related to color vision are carried on the X chromosome so a single error in one of the pigment genes is sufficient. Women are only color blind if both copies are defective.
aetherson 10y ago
Only women are capable of tetrachromacy because the gene that controls which wavelengths of light are detected by cones are on the X chromosome. Tetrachromat women have a mutation on one of their X chromosomes, and are heterozygous for "normal" cones (detect one wavelength) and "abnormal" ones (detect another wavelength). As it turns out, this means that some of their cones detect one wavelength of light, and others detect the other. As men can not be heterozygous for traits on their X chromosomes, they can't express two cones simultaneously. They CAN have the mutation, but that means they see three colors that are somewhat different from the three colors that other men see, not that they see four colors. All of the above as I understand it from a popular article on tetrachromacy. I am not a biologist.
- ryao 10y ago
  The alleles being sex linked makes sense, although there are a couple of theoretical exceptions. One is the very rare male that has two X chromosomes because the SR-Y gene was transposed onto the X chromosome. The other would be having the reverse where the second gene is transposed onto the Y chromosome. The former are sterile while I would guess that the latter are not sterile, but unless they really do exist, are found and one that is found has the same combination as a tetrachromatic woman, there is no way to confirm that. Genetics was one of my strong points when I was in school. I would have gone into bioinformatics if it were not for my poor performance in organic chemistry, which I felt crippled my ability to do the sort of work that I had wanted to do.
  - throwanem 10y ago
    You don't need to be good at orgo to do informatics; I've worked with a number of very capable analysts who hadn't been anywhere near a lab since their undergrad days. (If you want to do lab work, things are different, but my experience is that it's kind of rare for informatic analysis and lab work to overlap.) Another possibility for male tetrachromats would be people with the 47,XXY karyotype, who are phenotypically male but have the paired X chromosomes necessary to make tetrachromacy possible. Given the rarity of both variations, I can't imagine it being likely that any such person has been identified, but based on my (admittedly meager) knowledge of the subject, I don't see a theoretical barrier to such a person possibly existing.
jjtheblunt 10y ago
it could be a recessive trait carried on the X chromosome, and women have two copies of X, whereas men have an X and a Y, so could never satisfy the two copies criterion for recessive traits.
TeMPOraL 10y ago
> Having three primary colors never made much sense to me either, but that could just be my own ignorance. Tree primary colors thing seems to be mostly ignorance of the educators teaching that stuff to children. There are no absolute "primary colors" - basically, you can pick any colors at random and use them as a base for linear combinations; the set of colors you can express as such linear combinations form a color space defined by those base colors you picked. Red, green and yellow are a common historical picks, RGB is more common now because that's what is put on the computer screen, but CMY form a color space too. C.f.: https://en.wikipedia.org/wiki/Primary_color#/media/File:CIE1931xy_sRGB.svg https://en.wikipedia.org/wiki/Primary_color#/media/File:CIE1... - the triangle inside is the color (sub)space of RGB overlayed on CIE 1931 color space (https://en.wikipedia.org/wiki/CIE_1931_color_space https://en.wikipedia.org/wiki/CIE_1931_color_space). Source: I educated myself when I got asked by a local drunk to resolve a bet between him and (presumably) another local drunk while I was shopping in a local grocery store. Those two got into a bet over whether RGB or RGY are primary colors.
- Apocryphon 10y ago
  So who won, based on your exposition? Or was it a draw?
  - TeMPOraL 10y ago
    I left that for the two to settle between themselves. I just explained the thing to the guy that asked me first. He was on the RGB side, having shown me a picture similar to this one[0] on his mobile phone. My guess is that he ended up claiming victory, because when I tried to explain the details of the problem, he was going all "so this means RGB can be considered primary colors, right?". I never met the other guy. [0] - https://en.wikipedia.org/wiki/RGB_color_model#/media/File:AdditiveColor.svg https://en.wikipedia.org/wiki/RGB_color_model#/media/File:Ad...
- jimminy 10y ago
  RBY is what is commonly taught as primary bases in school, due to color compositions and the ease of expressing it through mixing pigments. R + B = Purple R + Y = Orange B + Y = Green
magic_beans 10y ago
> One involves "green" status LEDs on electronics, which seem more in common with yellow than green to me. I believe the word you're looking for here is "neon". A bright green. You don't have tetrachromacy, but you do sound like a delight at parties.
- sctb 10y ago
  Personal insults are not OK on Hacker News. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
  - magic_beans 10y ago
    Sigh, ok.
cgriswald 10y ago
I see some things that people identify as orange as more yellow. I am certain is has to do with all cones not being equal. You may have a cone that is more sensitive to a wider or narrow range; or one that has a peak sensitivity to a slightly different wavelength than the norm; or both.
throwanem 10y ago
>One involves "green" status LEDs on electronics, which seem more in common with yellow than green to me. Almost all "green" LEDs emit at a wavelength of 565nm, which is almost equidistant [1] between green and yellow. Most "green" LEDs are thus green solely by convention, and seeing them as greenish yellow (or yellowish green) isn't unusual at all, because that's the color they actually emit. You can find green LEDs that actually are green, but they're relatively uncommon, and tend to be costly unless you order in bulk direct from a manufacturer. [1] http://ledmuseum.candlepower.us/35/m-565re2.gif http://ledmuseum.candlepower.us/35/m-565re2.gif

by ryao 10y ago

rarec 10y ago

http://news.nationalgeographic.com/news/2012/09/120907-men-women-see-differently-science-health-vision-sex/ http://news.nationalgeographic.com/news/2012/09/120907-men-w... Men and women seeing slightly differently is in line with our biology. Just how it is, really. Men are more prone to color blindness too. https://nei.nih.gov/health/color_blindness/facts_about https://nei.nih.gov/health/color_blindness/facts_about

ryao 10y ago
That explains the LED thing. Thanks.

ChuckMcM 10y ago

Simplified version: X chromosome can express 1 or 2 color receptors, Y only expresses 1. Women (XX) can get up to 4, but the X occasionally only produces 1, since women have two X they mostly have 3, sometimes 4 and very very rarely only get 2 (both X only express only one) Men (XY) can get 3 but when the X chromosome only gives 1 they only have 2 and are color blind. Depending on which one they didn't get, that determines their color blindness. [1] http://www.radiolab.org/story/211193-perfect-yellow/ http://www.radiolab.org/story/211193-perfect-yellow/

maxerickson 10y ago
https://en.wikipedia.org/wiki/XY_sex-determination_system https://en.wikipedia.org/wiki/XY_sex-determination_system is a useful start for anyone not familiar with the very strong link between some genes and sex determination. The next step from there is that in humans the X chromosome carries more genes than the Y chromosome. Since women have two X chromosomes, they can express multiple variations of genes located there. Men will only possess one variation. This is the reason that color blindness is so much more common in men, some of the genes related to color vision are carried on the X chromosome so a single error in one of the pigment genes is sufficient. Women are only color blind if both copies are defective.

aetherson 10y ago

Only women are capable of tetrachromacy because the gene that controls which wavelengths of light are detected by cones are on the X chromosome. Tetrachromat women have a mutation on one of their X chromosomes, and are heterozygous for "normal" cones (detect one wavelength) and "abnormal" ones (detect another wavelength). As it turns out, this means that some of their cones detect one wavelength of light, and others detect the other. As men can not be heterozygous for traits on their X chromosomes, they can't express two cones simultaneously. They CAN have the mutation, but that means they see three colors that are somewhat different from the three colors that other men see, not that they see four colors. All of the above as I understand it from a popular article on tetrachromacy. I am not a biologist.

ryao 10y ago
The alleles being sex linked makes sense, although there are a couple of theoretical exceptions. One is the very rare male that has two X chromosomes because the SR-Y gene was transposed onto the X chromosome. The other would be having the reverse where the second gene is transposed onto the Y chromosome. The former are sterile while I would guess that the latter are not sterile, but unless they really do exist, are found and one that is found has the same combination as a tetrachromatic woman, there is no way to confirm that. Genetics was one of my strong points when I was in school. I would have gone into bioinformatics if it were not for my poor performance in organic chemistry, which I felt crippled my ability to do the sort of work that I had wanted to do.
- throwanem 10y ago
  You don't need to be good at orgo to do informatics; I've worked with a number of very capable analysts who hadn't been anywhere near a lab since their undergrad days. (If you want to do lab work, things are different, but my experience is that it's kind of rare for informatic analysis and lab work to overlap.) Another possibility for male tetrachromats would be people with the 47,XXY karyotype, who are phenotypically male but have the paired X chromosomes necessary to make tetrachromacy possible. Given the rarity of both variations, I can't imagine it being likely that any such person has been identified, but based on my (admittedly meager) knowledge of the subject, I don't see a theoretical barrier to such a person possibly existing.

jjtheblunt 10y ago

it could be a recessive trait carried on the X chromosome, and women have two copies of X, whereas men have an X and a Y, so could never satisfy the two copies criterion for recessive traits.

TeMPOraL 10y ago

> Having three primary colors never made much sense to me either, but that could just be my own ignorance. Tree primary colors thing seems to be mostly ignorance of the educators teaching that stuff to children. There are no absolute "primary colors" - basically, you can pick any colors at random and use them as a base for linear combinations; the set of colors you can express as such linear combinations form a color space defined by those base colors you picked. Red, green and yellow are a common historical picks, RGB is more common now because that's what is put on the computer screen, but CMY form a color space too. C.f.: https://en.wikipedia.org/wiki/Primary_color#/media/File:CIE1931xy_sRGB.svg https://en.wikipedia.org/wiki/Primary_color#/media/File:CIE1... - the triangle inside is the color (sub)space of RGB overlayed on CIE 1931 color space (https://en.wikipedia.org/wiki/CIE_1931_color_space https://en.wikipedia.org/wiki/CIE_1931_color_space). Source: I educated myself when I got asked by a local drunk to resolve a bet between him and (presumably) another local drunk while I was shopping in a local grocery store. Those two got into a bet over whether RGB or RGY are primary colors.

Apocryphon 10y ago
So who won, based on your exposition? Or was it a draw?
- TeMPOraL 10y ago
  I left that for the two to settle between themselves. I just explained the thing to the guy that asked me first. He was on the RGB side, having shown me a picture similar to this one[0] on his mobile phone. My guess is that he ended up claiming victory, because when I tried to explain the details of the problem, he was going all "so this means RGB can be considered primary colors, right?". I never met the other guy. [0] - https://en.wikipedia.org/wiki/RGB_color_model#/media/File:AdditiveColor.svg https://en.wikipedia.org/wiki/RGB_color_model#/media/File:Ad...
jimminy 10y ago
RBY is what is commonly taught as primary bases in school, due to color compositions and the ease of expressing it through mixing pigments. R + B = Purple R + Y = Orange B + Y = Green

magic_beans 10y ago

> One involves "green" status LEDs on electronics, which seem more in common with yellow than green to me. I believe the word you're looking for here is "neon". A bright green. You don't have tetrachromacy, but you do sound like a delight at parties.

sctb 10y ago
Personal insults are not OK on Hacker News. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
- magic_beans 10y ago
  Sigh, ok.

cgriswald 10y ago

I see some things that people identify as orange as more yellow. I am certain is has to do with all cones not being equal. You may have a cone that is more sensitive to a wider or narrow range; or one that has a peak sensitivity to a slightly different wavelength than the norm; or both.

throwanem 10y ago

>One involves "green" status LEDs on electronics, which seem more in common with yellow than green to me. Almost all "green" LEDs emit at a wavelength of 565nm, which is almost equidistant [1] between green and yellow. Most "green" LEDs are thus green solely by convention, and seeing them as greenish yellow (or yellowish green) isn't unusual at all, because that's the color they actually emit. You can find green LEDs that actually are green, but they're relatively uncommon, and tend to be costly unless you order in bulk direct from a manufacturer. [1] http://ledmuseum.candlepower.us/35/m-565re2.gif http://ledmuseum.candlepower.us/35/m-565re2.gif