This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
All of the following statements about sickle cell disease are true, EXCEPT: 
Select and explain. 
A. Point mutation results in change of Glutamic acid to Valine, B. RFLP results from a single base change, C. Sticky patch' is generated as a result of replacement of a non polar residue with a polar residue, D. HbS confers resistance against malaria in heterozygous individual
C: Sticky patch' is generated as a result of replacement of a non polar residue with a polar residue
Answer: C: Sticky patch' is generated as a result of replacement of a non polar residue with a polar residue 
Explanation: In sickle cell disease glutamic acid is replaced by valine at the 6th position of the beta chain. This substitution replaces a polar glutamate residue with a non polar valine residue. As a result of this replacement a sticky patch is generated on the surface of the beta chain. This hydrophobic patch provides a surface that complements another surface feature of hemoglobin present only in the deoxygenated form. As a result, HbS in the deoxy form polymerises, forming long fibrous precipitates in the rbc. RBC distos taking on a sickle shape, and is vulnerable to lysis as it penetrates the interstices of splenic sinusoids. Ref: Medical Biochemistry: Pearls of Wisdom By Duane C. Eichler, Page 44 ; Lecture Notes on Clinical Biochemistry By Alistair Fairley Smith, Page 273 ; Human Heredity: Principles and Issues By Michael R. Cummings, Page 471