Question

Explain the inheritance pattern of colour blindness with a suitable chart.

Answer 1

1. A person suffering from colour blindness cannot differentiate between red and green colours. Both these colours appear grey to the colour blind person.
2. It is caused due to recessive X-linked genes (Xc ) which prevent the formation of colour sensitive cells in the retina that are necessary for distinguishing red and green colours.
3. Dominant X linked gene (XC ) is necessary for the formation of colour sensitive cells in the retina of the eye.
4. The homozygous recessive females (Xc Xc ) and hemizygous recessive male (Xc Y) are unable to distinguish between red and green colours. The frequency of colour of blind women is much less than colour blind men.
5. When a normal man marries a carrier woman, half of their sons may be colour blind, while the remaining half will have normal vision. All their daughters will have normal vision and half of them will be carriers for the disease.
6. If a colour blind male (Xc Y) marries a female with normal vision (XC XC ), then all the offsprings will have normal vision. The sons will have normal vision but daughters will be carriers for the disease. The carriers have normal vision.