Understanding more about colour blindness

What are the different types of colour blindness?

Colour blindness can be categorized among many types. Based on clinical appearance, colour blindness may be described as total or partial. Total colour blindness is much less common than partial colour blindness. There are two major types of colour blindness: those who have difficulty distinguishing between red and green, and who have difficulty distinguishing between blue and yellow.

What a normal person would see is:

However, a colour blind person who has difficulty distinguishing between red and green would see these instead:

A person who has difficulty distinguishing between blue and yellow will see this:

Why do these people get colour blindness?

Colour blindness is a sex linked recessive condition, which means that it is a recessive trait condition which is transmitted in the 23 pair of chromosomes.

Males only have one X chromosome in their 23rd pair which means they can either have normal vision or be affected, they cannot be carriers. the genotype of the 23rd pair of chromosomes (while X=normal and X^R = affected) would be:

For a male with normal vision, XY

For a male with colour blindness, X^RY

Because males have only one X chromosome in their 23rd pair, they have a higher chance of inheriting colour blindness, this is why more males in the population have colour blindness then females.

For a female with normal vision, XX

For a female with normal vision but a carrier, X^RX

For a female with colour blindness, X^RX^R

Sources:
http://en.wikipedia.org/wiki/Color_blindness
http://colourblind.freeservers.com/how.htm