Most of my blogs have focused around what it is like to have colour blindness and how to work around the condition, but I haven’t said a lot on the actual science behind the condition. So this blog will aim to fix that! I hope you will learn something new and I also hope this will create a little bit more understanding about the condition.
How do you get colour blindness?
Don’t worry colour blindness isn’t contagious, so you aren’t going to catch it by being near colourblind people (although you should be keeping a 2 meter distance anyway). Colour vision deficiency, or as it is commonly known as: colour blindness, is a mostly genetic condition that is inherited through the x chromosome. It should be said that some other diseases have been seen to cause colour blindness such as diabetes, glaucoma, multiple sclerosis, and age-related macular degeneration. Also some drugs might have the side effect of giving you colour blindness and being exposed to harmful chemicals can do it also.
Ok, let's get into the meaty science behind colour blindness. To be colour blind all your x chromosomes need to be affected. Men have one x chromosome and one y chromosome. Women have two x chromosomes. This is why there are more men affected by the condition. Men receive the x chromosome from their mothers and the y chromosome from their fathers, meaning that if their mother has one affected x chromosome, there is a 50% chance that they will be colour blind. Women recieve one x chromosome from the mother and the other from their father, so there is a 50% chance that they will be a carrier.
If a carrier woman had children with a colour blind man, again there is a 50% chance that the son will be colour blind, but the daughters will definitely be a carrier, with a 50% chance of being colourblind.
If a colour blind woman had children with a man with normal vision, then all the son has a 100% chance of being colour blind and the daughter has a 100% chance of being a carrier.
If a colour blind woman had children with a colour blind man, then all the children will be colour blind.
What Causes Colour Blindness?
I briefly touched on this in my very first blog (give it a read), but it has all got to do with the cones in your eyes. The eye has 3 cones: the S cone, for short wavelengths, the M cone, for medium wavelengths, and the L cone, for long wavelengths. When light enters the eye it stimulates the cones, however cones aren’t good at detecting colour on their own, they need the other cones to narrow down what colour it is you are seeing. It should be noted that all the images below are just one example of each form of colour blindness.
There are conditions called anomalous trichromacy, which means you have all your cones, but they are shifted closer together, making it harder for the brain to distinguish certain colours.
Another type of colour blindness is dichromacy, where an entire cone is missing from your eye. This means that the eye is unable to detect certain colours. For example protanopia, what I have, is when the entire L cone is missing, so my brain can’t detect certain colours when it looks at it.
The is a rare condition called monochromacy, when 2 cones are missing from the eye. Since a single cone can’t see colour on its own, people with the condition see in completely black and white.
Sheesh. That was a lot of big words. Anyway I hoped this helped people understand how colour blindness is caused and how it is inherited. When researching for this blog I found this great video on colour blindness by Human Interests, called “How Color Blindness Works”. I recommend you check it out and some of the other videos on his channel if you want to learn more about colour blindness. Thanks for reading.
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