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?
1) altered primary structure
2) altered secondary structure
3) altered tertiary structure
4) altered quaternary structure
5) altered primary structure and altered quaternary structure; the secondary and tertiary structures may or may not be altered