Read the following statements about sex-linked disorders. (i) Red-green colour blindness is due to a defect in either the red or the green cone of the eye. (ii) Colour blindness occurs in about 8 per cent of males but only about 0.4 per cent of females. (iii) The son of a woman who carries the gene for colour blindness has a 50 per cent chance of being colour blind. (iv) A daughter of a carrier mother is not colour blind unless her father is colour blind. (v) A haemophilic female is extremely rare, because her mother must be at least a carrier and her father haemophilic. (vi) Queen Victoria was haemophilic, and so several of her descendants were haemophilic. How many of the statements above are correct?