Hereditary spherocytosis is due to defect in:

Ans: A (Spectrin) Ref: Robbins, 7th ed, p. 625-626; Harrison, 16th ed, p. 609-610,17 ed, p. 653It is an inherited disorder due to intrinsic defects in the red cell membrane that render red cells spheroid, less deformable and vulnerable to splenic sequestration and destruction.The remarkable elasticity and durability of normal red cell is due to physiochemical properties of its membrane skeleton, the chief component of which is spectrin.Spectrin forms a tetramer that can bind with actin oligomers forming a two dimensional actin-spectrin skeleton.This actin- spectrin skeleton is connected to cell membrane by two distinct interactions.They are:1) Ankyrin and protein 4.2 binds spectrin to bond 32) Protein 4.1 binds spectrin to glycophorin AHS may be due to mutations affecting any of these protein; in the order of decreasing frequency mutations are:1) Mutations affecting ankyrin--50% cases2) Mutations affecting protein 3 (anionic transport channel)--25% cases3) Mutations affecting spectrin--25% cases4) Mutations affecting palladin (protein 4.2)--rare