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 fibres.Based on this information alone,we can conclude that sickle-cell hemoglobin exhibits
A)altered primary structure. B)altered secondary structure. C)altered tertiary structure. D)altered quaternary structure. E)altered primary structure and altered quaternary structure; the secondary and tertiary structures may or may not be altered.