The heritable disease caused by distorted shape of the red blood cell, hindering free flow of blood in the vessel is

Sickle cell anaemia is the heritable disease characterised by distorted (sickle or crescent-shaped) red blood cells. It is caused by a point mutation in the gene encoding the beta-globin subunit of haemoglobin, where the amino acid glutamic acid is replaced by valine at position 6. This produces an abnormal form of haemoglobin called haemoglobin S (HbS). Under low oxygen conditions, HbS molecules polymerise and cause the red blood cells to become rigid and sickle-shaped, rather than their normal biconcave disc shape.

These distorted cells are inflexible and tend to clump together, blocking small blood vessels and hindering the free flow of blood. This leads to painful crises, tissue damage from oxygen deprivation, and chronic anaemia because the sickle cells are fragile and break down more rapidly than normal red blood cells.

Haemophilia is a heritable bleeding disorder caused by deficiency of clotting factors, not by distortion of red blood cells. Albinism is the lack of melanin pigment production. Colour blindness is the inability to distinguish certain colours due to defective cone cells in the retina. None of these involves abnormal red blood cell shape.