Sickle-cell anemia is associated with a mutation in the gene encoding the beta subunit of hemoglobin that results in a change from glutamic acid to valine at position 6. All other amino acids are identical to a normal hemoglobin molecule.

Based on the information above, which of the following mutations is the most likely cause of sickle-cell anemia?

Since only one amino acid changed, the mutation is unlikely to have changed the reading frame. An insertion or deletion mutation would change the reading frame and cause every amino acid after the mutation to be modified. A translocation of DNA would dramatically alter the protein product.