In the described sickle cell mutation, which amino acid change occurs?

• A. Glycine to Valine
• B. Valine to Glutamic acid
• C. Glutamic acid to Valine
• D. Leucine to Phenylalanine

Answer: (C)

A single-nucleotide change in the beta-globin gene causes a missense mutation that alters one amino acid in the protein. In sickle cell disease, the sixth amino acid of beta-globin changes from glutamic acid, which is charged and water-loving, to valine, which is hydrophobic. This Glu-to-Val substitution changes how hemoglobin behaves, especially when oxygen levels are low, leading to polymerization and the characteristic sickling of red blood cells. That’s why the correct description is Glutamic acid to Valine. The other possible substitutions would involve different amino acid changes and do not match the well-known sickle mutation.