What causes colour blindness?

Answer 1

Originally, the creatures we evolved from only had monochrome vision. Then we evolved two different types of colour detector (blue and red/green), and then the red/green type evolved into separate detectors, giving us our current 3-colour vision.

The genes encoding for the red vs green detectors are on the X chromosome, so men only have one copy. If the other copy is faulty - if instead it codes for the old red/green combined detector - the man will not be able to distinguish red from green, and will be red/green colour-blind (it is also possible to be blue/green or red/blue colour-blind, but this is much rarer).

Women are colour-blind more rarely because they have two copies, and BOTH have to be faulty.

Answer 2

A genetic lack of cone cells in the retina is what causes colour blindness (aka "dischrompatopsia").

The retina contains two kinds of photoreceptor cells - rods and cones. Rods work under low light conditions, but cannot distinguish between different wavelengths (colours) of light, which is why you only see in B&W at night.
Cone cells only work under fairly intense illumination, and have three sub-types: red, blue, and green. Each of these detects that particular wavelength of light, and this allows you to see in colour. If you have a lack of red cone cells, then the next one (green) detects most of the light at that end of the spectrum - so you can still see things that are red, but you have difficulty distinguishing different colours in the red/yellow/orange end of the spectrum.

This kind - red/green colour blindness - is the most common form. There are others (at the blue end of the spectrum), but these are much rarer.

Edit:
(in response to Kimberley)
The red/green forms of colour blindness *are* indeed sex-linked, so they affect men much more often than women. But this is because the affected gene is on the X chromosome, not the Y chromosome. Men do not have a second X chromosome, so any defect of the X chromosome cannot be "masked" by any dominant traits on its "partner" - and this is why sex-linked diseases affect men much more often than women.
Y chromosomes are almost "genetically empty", containing only ~78 known genes in comparison to the X chromosome's ~2000. The only well-defined genetic defect linked to a allele on the Y chomosome is a defect in testicular development.

Answer 3

Colour

Answer 4

you have cones in the back of your eyes that recognise colours, we have primary colours red, blue and green (there are different primary colours from art and science lol) and sometimes your cones won't recognise the colour properly and that will lead to colour blindness like getting the colours green and red mixed around for instance, this is caused by a genetic defect. hope this helps, must have sounded like a right geek lmao, but i had a lesson in science about this the other day lol so thought i'd share it with ya hehe. xXx

Answer 5

Hi, My son is colour blind,(with red/green) i found out when he was 11 years old. I took him to a eye doctor and he told me that it is genetic, he had most probably got the defective gene from me as it more often than not comes from the mother, i was also asked if my father was colour blind as the mother gets the gene from her fathers side of the family.

Answer 6

The reason men tend to be coloured blind is because colour blindness is a recessive trait, this means you need 2 faulty genes (one from each parent) for it to be expressed in the offspring. The faulty gene is carried on the X chromosome, this means that for a man to inherit colour blindness he only needs one copy of the gene whereas a female would need to inherit the faulty gene from both parents (otherwise the good dominant gene on their other X would . . .well dominate!).

We all have 2 main types of receptor in our eyes, rods and cones. Rods allow us to see in the dark and in low lighting whereas cones allow us to see in colour. The faulty gene affects the cones in our eyes and therefore we cannot perceive colour.

xxx

Answer 7

Kimberly is wrong the defective gene is on the X chromosome. As a man only has one X he is not protected like a woman who has a 'spare' X chromosome. However if a woman gets TWO defective X chromosomes she will be colour blind as well. This is quite rare.

Answer 8

Not being able to see colours causes colour blindness.

Answer 9

Generally it's a genetic character. If your father or mother or grandparents had colour blindness then their are chances of you getting colour blinded.

Answer 10

COlour blindness is of two types protonopia and deutronopia.cause due to absence of erythrolabe (red colour blindness) and chlorolabe(green colourblindness).so these two pigments make all the difference.
hope it would help you