Normal hemoglobin is a tetramer, consisting of two molecules of β hemoglobin and two molecules of α hemoglobin. in sickle-cell disease, as a result of a single amino acid change, the mutant hemoglobin tetramers associate with each other and assemble into large fibers. based on this information alone, we can conclude that sickle-cell hemoglobin exhibits

changed primary and quaternary structures.

Explanation:

Proteins are the polymers of amino acids. The amino acid sequence of a protein makes its primary structure. A point mutation in the beta-globin gene results in the substitution of polar amino acid glutamate with non-polar amino acid valine. Therefore, the mutation changes the primary structure of the protein hemoglobin.

Hemoglobin is a multi-subunit protein. Arrangement of two beta and two alpha subunits in three-dimensional complexes makes its quaternary structure. The mutation responsible for sickle cell anemia makes the subunits of hemoglobin to assemble into large fibers. Hence, the quaternary structure of the protein is also altered.