Question

What do you mean by colour blindness?

Answer 1

Color Blindness:

• It is a hereditary eye disease. It was first described by Horner. It is of 3 types –
  
  
  
  1. Red-green colour blindness
  2. Blue - Yellow color blindness
  3. Total color blindness


• The red-green color blindness is most common & it is also called a protan defect. Red-green color blindness is caused due to the absence of red-green cones in the retina.
• The person is unable to identify red, green, yellow & orange colours. These colours appear to be green in the absence of red cones and they appear to be red in the absence of green cones.
• It is a sex-linked disease which is caused due to a recessive gene on the X-chromosome. The mother (female) acts as a carrier. The father of a color blind daughter is always colourblind.
• In the $F_1$ generation of carrier mother & normal father, 50% generation will be normal, 25% will be carrier & 25% will be colourblind.


• In F1 generation of carrier mother and colourblind father, 50% of daughters will be colourblind & 50% will be carrier likely, 50% of boys will be normal & 50% will be colourblind.


• In the $F1$ generation of normal mother & colourblind father, all males will be normal and all daughters will be a carrier.