A Single Mutation Causes Sickle-Cell Disease

A single mutation causes sickle-cell disease. Which of the following statements best describes how this occurs?

A) A single nucleotide mutation causes a normal glutamic acid amino acid to be replaced with a valine amino acid. This causes the resulting hemoglobin protein to form incorrectly, resulting in sickle-shaped red blood cells that cannot function as intended.
B) Three nucleotide mutations cause normal glutamic acid amino acids to be replaced with valine amino acids. This causes excess hemoglobin proteins to be synthesized, causing red blood cells to swell to the point of bursting, resulting in burst cells that have a sickle-shape.
C) Several nucleotides are removed, which causes the start codon to shift. This results in an incorrect number of amino acids to be incorporated into the hemoglobin protein, leading to the sickle-shaped red blood cells.
D) The addition of several nucleotides causes the start codon to shift down several places. This causes RNA polymerase to bind in the incorrect spot so that several extra amino acids are included in the polypeptide chain during translation. This results in a hemoglobin protein that is incorrectly formed, resulting in sickle-shaped red blood cells that cannot function as intended.