Final answer:
The antibody affinity is determined by the amino acid sequence in the variable regions of the immunoglobulin molecule, not in the constant regions.
Step-by-step explanation:
The antibody affinity, or the strength of binding between an antibody and antigen, is not determined by the amino acid sequence in the constant regions of the immunoglobulin molecule. Instead, it is determined by the amino acid sequence in the variable regions of the immunoglobulin molecule. The variable region contains the antigen-binding site, where the antibody binds to the specific epitope on the antigen. The amino acid sequence in the variable region dictates the three-dimensional structure of the binding site and therefore determines the specificity and affinity of the antibody for the antigen. On the other hand, the constant regions of the antibody molecule determine its class, or isotype.