SCD is caused by a recessive, single-nucleotide mutation in the beta globin gene of Hgb. All of the following are TRUE about Sickle cell disease, EXCEPT:: (A) Single nucleotide change results in change of Glutamine to Valine, (B) Sticky patch is generated as a result of replacement of a non polar residue with a polar residue, (C) HbS confers resistance against malaria in heterozygotes, (D) RFLP results from a single base change
Answer is B. When the sickle Hgb unloads its O2, the normal conformational change exposes the valine at position 6 to the surface creating a "hydrophobic (sticky) patch". The hydrophobic patch on one deoxygenated Hgb molecule can interact with the hydrophobic patch on a second Hgb molecule, creating stiff Hgb polymers. These internal polymers cause the RBC to stiffen and adopt abnormal shapes, including a crescent or "sickle" shape that gives the disease its name. Ref: Poeus M., Mantanona T. (2012). Chapter 14. Blood. In L.W. Janson, M.E. Tischler (Eds), The Big Picture: Medical Biochemistry.