Pleiotropic gene has more than one effect in an organism, eg, sickle cell anaemia which results due to abnormal haemoglobins.
Thalassaemia is a blood disease caused by a substitution mutation in the DNA sequence that controls the synthesis of the α or β-chain of haemoglobin. It results in anaemia and growth retardation.
Haemophilia is a hereditary sex-linked disease, in which there is a deficiency or defect of factor-VIII, causing the blood to clot very slowly.
Leukaemia or Cancer of WBCs is any disorder of cell growth that results in invasion destruction of surrounding healthy tissue by normal cells.