| DISEASE | SYMPTOMS | CAUSES |
| ALBINISM | Lack of dark pigment melanin in the skin , an albino is susceptible to eye disorders due to damaging effect of bright light. | Caused by absence of enzyme tyrosinase which convert dihydroxyphenylalanine into melanin. Only homozygous individuals are effected. |
| RED GREEN COLOUR BLINDNESS—— Sex linked recessive inheritance | Inability of individual to differentiate between red & green colour. | X linked recessive gene is responsible for it causing lack of one of the primary cone pigments of retina. Male has only one X chromosome hence if it is defective then they are colour blind but in female if one X chromosome is defective then they are carrier and if both X chromosomes are defective then they show colour blindness. |
| NIGHT BLINDNESS—–It is of two types acquired and congenital | Unable to see in dark. In acquired one it is due to vitamin A deficiency. & In congenital it is sex linked trait recessive gene carried by X chromosome. | Effect on male and female is in the same way as in colour blindness. |
| MUSCULAR DYSTROPHY | Deterioration of muscles at an early age. Victim becomes invalid by the age of 10 and usually dies by the age of 20. | The mutated gene on X chromosome fail to produce a protein dystrophin this protein signal to the calcium storage sac in the muscle in its absence calcium is not released hence abnormal calcium level trigger the release of enzyme that destroys actin and myosine. |
