In the germinal center reaction, which molecular event is responsible for generating antibodies with higher affinity for antigen during B-cell maturation?

• A Somatic hypermutation catalyzed by Activation-Induced Cytidine Deaminase (AID) ✓
• B VDJ recombination by RAG1/RAG2 enzymes
• C Class switch recombination from IgM to IgG
• D Receptor editing to replace the light chain V region

Explanation

Somatic hypermutation (SHM) is catalyzed by AID which deaminates cytosine to uracil in the variable regions of Ig genes, introducing point mutations; B cells with higher affinity mutations are positively selected by follicular dendritic cells presenting antigen (affinity maturation). VDJ recombination occurs in the bone marrow during initial B-cell development, not in germinal centers. Class switch recombination changes the isotype (constant region) but not antigen-binding affinity. Receptor editing removes self-reactive receptors during tolerance induction.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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