The Biology behind Red-Green Color Blindness
- Posted by Daniel Flück on March 7th, 2006 filed in Academic
- 24 Comments »
Red-green color blindness is in the majority of cases provoked through a defective X-chromosome. Human beings have 23 different pairs of chromosomes whereof one pair is the so called sex-chromosome. This pair consists of two X-chromosomes on women and one X- coupled with one Y-chromosome on men. Color vision in the red-green area is coded on the X-chromosome which is called a sex linked trait.
This concludes if a man is a carrier of a defective X-chromosome he will suffer from color blindness. On women the not defective chromosome is in charge and therefore she is not colorblind but a carrier for color blindness. Because a women needs two defective X-chromosome to be affected this symptome is called X-linked recessive. A very interesting conclusion of this: If you are male and your father suffers from a red-green color vision deficiency you can not inherit it from him. Only women can be carriers for color blindness who pass it on to their sons.
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Let’s have a look at some illustrations. On the left you can see how the disorder is passed on from an affected father to his children. The sons are unaffected and do not have the mutation. The daughters are not affected but are both carriers of the disorder because they inherited the defective X-chromosome from their father. The illustration on the right side shows a mother which is a carrier and a father which is unaffected. Their son is at a rate of 50% affected i.e. red-green colorblind and their daughter is at the same rate either are carrier or unaffected.
In the last illustration we coupled an affected man with a women which is a carrier. As you can see their children are at a rate of 50% affected. This is the only case shown here, where a women can be affected i.e. suffering from a red-green color blindness. If the children are unaffected the daughter is anyway a carrier of the disorder. The not shown combinations where man and women are either both affected or both unaffected are left to the reader…
I hope this could give a better insight into the biology behind color blindness. It has to be noted that these remarks are only true for red-green color blindness. Blue-yellow color blindness (tritanopia) is linked to the chromosome pair 7 and therefore sex independent. Further readings on this topic and more details can be found under the following links:
The above illustrations are provided by the U.S. National Library of Medicine, 7th March 2006.
24 Responses to “The Biology behind Red-Green Color Blindness”
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March 8th, 2006 at 1:12
A couple of posts ago on my blog you asked me if I had the url’s of the blogs I quit reading because of my color-blindness. I don’t have them but I just ran across a couple that are extremely difficult for me to read. One of them is this: http://lamonalicious.blogspot.com/
I can read this one but it’s very difficult. It’s not like the one’s I ran across that were invisible to me, but this one is more trouble than it is worth.
Sorry, I just went back to look for the other and I already lost it.
I’m red/green color blind like you. You explain it quite well on here. I get asked all the time, “If you’re color blind, what color is this?” I try to explain it to them, but I don’t do a very good job.
Thanks for stopping by.
March 8th, 2006 at 11:01
bornfool,
thanks for stopping by and making investigations to answer my question. I had a look at the blogsite you posted: the titles are what bothers me most. They are popping out, making me almost dizzy.
I hope with my blog people can get a better understanding of colorblindness and can answer the question “what color is this?” by themselfs.
December 18th, 2006 at 17:50
Hello, i love http://www.color-blindness.com! Let me in, please :)
June 2nd, 2007 at 14:47
i red/green color blindness. i have question. my father is red/green color blindness but my mother is not. according to the chart i should not have it but why am i a red/green blindness?
June 2nd, 2007 at 15:35
Mike: you didn’t inherit the color blindness from your father, that’s for sure. But your mother can be a carrier and maybe the father of your mother is colorblind? It’s often passed on from grandfathers to their grandson.
July 12th, 2007 at 10:41
[...] Daniel Flueck – The Biology behind Red-Green Color Blindness [...]
February 7th, 2008 at 12:47
I belong to the very few women affected. That made it impossible for my father to pretend I wasn’t his daughter;-))
August 30th, 2008 at 1:44
[...] shocking news. Although Brandon’s vision tested at 20/20, he is apparently red-green colorblind. They did the Ishihara test on him via a book that he was to look through and say the numbers, [...]
October 13th, 2008 at 10:28
My mom is color blind and so all of her sisters, all of her sisters boys and girls are color blind… BUT i am not color blind… i smell sumthing fishy….
November 2nd, 2008 at 22:27
Here’s a question for experts: according to a vision test in a magazine she did recently, my mother has a slight red-green weakness, which, however, is hardly noticable in daily life. Is this also ‘colour blindness’, although that is really rare in women, and it’s nothing compared to her father’s colour blindness, which was pretty severe? Or can it be due to her being a carrier?
November 14th, 2008 at 22:34
Leonora, an interesting question which I tried to answer in the article If a Women is a Carrier of Color Blindness does she also Suffer from it?.
November 17th, 2008 at 23:25
Hi Daniel, thanks for your fascinating explanation. I’ve written a comment in the other thread.
March 17th, 2009 at 14:02
I am also colorblind. (color dumb if you ask my grandfather. My father and my grandfather on my mom’s side are colorblind. What are the chances of any of my kids being colorblind? My husband and his family are not.
March 17th, 2009 at 21:02
Danielle, I suppose you’re talking about red-green color blindness. In this case both of your X chromosomes are colorblind. This results in: all your boys will be colorblind and all your girls will not be colorblind (because your husband isn’t). That’s at least what the genetic inheritance patterns tells us.
September 17th, 2009 at 9:14
[...] #03 Color blindness is more prevalent among males than females, because the most common form of color vision deficiency is encoded on the X sex chromosome. [...]
December 25th, 2009 at 20:53
Thank you, it was interesting. Have more to these posts.
January 10th, 2010 at 17:19
I discover that I have red-green color blindness, but in fact I have perfect color vision as well. I have taken tests where I pass all colors but I can see double images in the pictures used for red-green color blindness tests. Is it possible that this can be an “added feature” to my color vision? or am I finding ghosts in dark rooms?
February 24th, 2010 at 22:37
“added feature” to my color vision? or am I finding ghosts in dark rooms?
October 12th, 2010 at 22:42
OK, I’m hoping a question can be answered for me. My youngest daughter – 3 1/2 years old – appears to be red/green color blind. We have thought this for about a year and a half – she knows ALL of her colors (even lights & darks now) but gets red or green wrong about half the time (so, if something is red there’s a 50/50 chance she will say red or green). This morning she seemed to confirm that she might be red/green color blind when she said to me, “Mom, red and green are the same color, right?” Here’s my question…
According to this description of genetics, the only way she could be affected would be if I were a carrier and my husband was affected. I don’t know of anyone in my family who is color blind, but regardless of that, my husband is NOT color blind. How could this be?? Any explanations would be really appreciated!
October 20th, 2010 at 22:13
Em, just some thoughts about your daughter:
- this is still a very young age to tell if someone is colorblind or not,
- different severity occur, so maybe there is someone colorblind you don’t know about,
- color blindness can be inherited down through many generations,
- genetics is not always a straight calculation. There are many other factors who can influence it.
So, please be patient – and don’t worry.
- Daniel
February 5th, 2011 at 13:24
Here is a question, what if a red-green colorblind man conveives children with a blue-yellow colorblind woman?
February 17th, 2011 at 18:54
Myrtonos, nice question. None of them will be colorblind. – But this is only working in an ideal world. So we actually don’t really know. – And the genetics I leave to you.
February 19th, 2011 at 1:25
But there are surely cases of this happeing. You say none of them will be colorblind but I wonder if in fact it might result in better than average color vision.
February 26th, 2011 at 23:46
Okay, what if say a red weak or green week man coceives children with a blue weak woman?
I know that if say a green weak man such as Mr. Tomoiag? were to conceive children with the daugther of a red weak man, their daugters could very well have both normal and anomoulous red cones and thus see *more* colours than normal.