CDR AGY Ser codons play a key role in affinity maturation. (A) Ratio observed over expected for synonymous codons in CDR sequences of combined IgV genes (VH, Vκ, and Vλ). (B) Percentage of the total contact residues that were created by SHM in V-region sequences only. Each data set represents a germline-encoded codon given rise to any contact residue. Black bars represent the percentage of AGY Ser codons that gave rise to a key contact residue defined by Raghunathan et al. (19).