Which description is NOT true for antibodies?

Which description is NOT true for antibodies?

• A. They have a "Y" shape.
• B. The heavy chains and light chains are identical in all antibodies.
• C. They are immunoglobulins.
• D. The amino sequence of the short arms of the "Y" is what distinguishes one antibody from another.

Answer: (B)

Antibodies are immunoglobulins with a Y-shaped structure built from heavy and light chains, and their diversity comes from the variable regions that form the antigen-binding sites in the Fab arms. The amino acid sequence in these short arms of the Y varies between antibodies, and this variation is what determines which antigen the antibody recognizes. The statement claiming that heavy chains and light chains are identical in all antibodies isn’t true because antibodies come in different isotypes and light-chain types, and their variable regions are generated through rearrangement to create a huge diversity of binding sites. In a given antibody, the two heavy chains are the same as each other and the two light chains are the same as each other, but across all antibodies there is variation.

Antibodies are immunoglobulins with a Y-shaped structure built from heavy and light chains, and their diversity comes from the variable regions that form the antigen-binding sites in the Fab arms. The amino acid sequence in these short arms of the Y varies between antibodies, and this variation is what determines which antigen the antibody recognizes. The statement claiming that heavy chains and light chains are identical in all antibodies isn’t true because antibodies come in different isotypes and light-chain types, and their variable regions are generated through rearrangement to create a huge diversity of binding sites. In a given antibody, the two heavy chains are the same as each other and the two light chains are the same as each other, but across all antibodies there is variation.