How many standard amino acids are there?

How many standard amino acids are there?

• A. 22
• B. 18
• C. 20
• D. 24

Answer: (C)

Twenty standard amino acids form the canonical set used to build proteins. The genetic code translates codons into these twenty amino acids, and many codons can specify the same amino acid, a feature called degeneracy. This redundancy helps protect against point mutations and allows efficient translation. In some specialized contexts, organisms can use nonstandard amino acids like selenocysteine or pyrrolysine, which expands the diversity in certain cases, but the standard, widely used set remains twenty.

Twenty standard amino acids form the canonical set used to build proteins. The genetic code translates codons into these twenty amino acids, and many codons can specify the same amino acid, a feature called degeneracy. This redundancy helps protect against point mutations and allows efficient translation. In some specialized contexts, organisms can use nonstandard amino acids like selenocysteine or pyrrolysine, which expands the diversity in certain cases, but the standard, widely used set remains twenty.