What is criss cross inheritance? Explain the inheritance of one sex linked recessive character in human beings.

Criss cross inheritance: It is a type of inheritance in which X-linked recessive genes are transmitted from a father to a grandson through a carrier daughter of the first (F₁) generation.
Example: Colour blindness, haemophilia, DMD.

Colour blindness: It is a sex-linked recessive disorder. Retina of the eye in man contains cone cells sensitive to red and green colour.

• The alleles for color vision are located on the X-chromosome.
• It is the inability or decreased ability to see certain colours.
• Example: Protonopia (Red colour blindness)
• Colour blind female always have colour blind father and mother carrier or affected for colour
  blind.
• Colour blind male always have carrier/colour blind mother.
• When woman with normal vision (homozygous) marries a colour blind man all the sons and daughters are normal,but daughters are carriers (heterozygous).
• If a carrier woman marries a man with normal vision all the daugthers have normal vision.
• Half of the sons have normal vision and another half of the sons are colour blind.