USMLE STEP 1 QUESTION ON DEMAND

The LDL cholesterol of baby with known familial hypercholesterolemia is 605mg/dl,although baby's plasma triglyceride levels are normal.Molecular genetic studies of cells isolated from baby indicate 10% LDL receptor activity and 10% of normal amount of LDL receptors on the cell surface.Further in vitro studies with receptor indicate a normal equilibrium B/W bound and free LDL at PH=7.0,but an unusually high amount of bound LDL at PH=6.0.Which of the following mutation best explain these data

A.complete blockade of transport of LDL receptor B/w endoplasmic reticulum and golgi apparatus
B.increased lysosomal degradation of LDL receptor
C.nonfunctional promoter in LDL receptor gene
D.poor interaction with coated pit,resulting in poor internalization of LDL receptor_LDL complex
E.reduced binding of LDL to its receptor

SENT BY: DR. D MANJUNATHA, BANGALORE