All of the following statements about sickle cell disease are true, EXCEPT:
Point mutation results in change of Glutamic acid to Valine
RFLP results from a single base change
Sticky patch' is generated as a result of replacement of a non polar residue with a polar residue
HbS confers resistance against malaria in heterozygous individual
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