Which HLA allele differs from A*02:01:02 by a synonymous nucleotide substitution?

Which HLA allele differs from A*02:01:02 by a synonymous nucleotide substitution?

• A. A*01:01:01:01
• B. A*02:02
• C. A*02:03:01
• D. A*02:01:03

Answer: (D)

In HLA naming, two alleles can produce the same protein even though their DNA sequences differ. A synonymous nucleotide substitution changes a codon to a different codon that encodes the same amino acid, so the protein sequence stays unchanged. The third field in the name captures these silent coding changes, while the first two fields define the protein and the fourth field covers non-coding region differences. A*02:01:03 differs from A*02:01:02 by such a silent codon change, preserving the same amino acid sequence. The other options either belong to a different allele group or would alter the protein sequence (non-synonymous changes) rather than being silent.

In HLA naming, two alleles can produce the same protein even though their DNA sequences differ. A synonymous nucleotide substitution changes a codon to a different codon that encodes the same amino acid, so the protein sequence stays unchanged. The third field in the name captures these silent coding changes, while the first two fields define the protein and the fourth field covers non-coding region differences.

A02:01:03 differs from A02:01:02 by such a silent codon change, preserving the same amino acid sequence. The other options either belong to a different allele group or would alter the protein sequence (non-synonymous changes) rather than being silent.