Which term best describes a three-base sequence on mRNA that encodes an amino acid?

Which term best describes a three-base sequence on mRNA that encodes an amino acid?

• A. Codon
• B. Anticodon
• C. Nucleoside
• D. Polymerase

Answer: (A)

A codon refers to a three-base sequence on messenger RNA that encodes a specific amino acid. In translation, the ribosome reads these codons and matches them with transfer RNA molecules that bring the corresponding amino acid, guided by the genetic code. The reason this term fits best is that codons are defined precisely as the triplet on mRNA that specifies which amino acid to add next during protein synthesis. Anticodon is the counterpart on tRNA that pairs with the codon, not the sequence on mRNA itself, so it doesn’t encode amino acids directly. A nucleoside is a sugar-plus-base unit (part of a nucleotide) and is not itself a coding triplet. A polymerase is an enzyme that synthesizes nucleic acids, not a three-base coding unit on mRNA. The triplet nature of codons also explains how there are enough combinations (64 possibilities) to cover all amino acids and stop signals.

A codon refers to a three-base sequence on messenger RNA that encodes a specific amino acid. In translation, the ribosome reads these codons and matches them with transfer RNA molecules that bring the corresponding amino acid, guided by the genetic code. The reason this term fits best is that codons are defined precisely as the triplet on mRNA that specifies which amino acid to add next during protein synthesis.

Anticodon is the counterpart on tRNA that pairs with the codon, not the sequence on mRNA itself, so it doesn’t encode amino acids directly. A nucleoside is a sugar-plus-base unit (part of a nucleotide) and is not itself a coding triplet. A polymerase is an enzyme that synthesizes nucleic acids, not a three-base coding unit on mRNA. The triplet nature of codons also explains how there are enough combinations (64 possibilities) to cover all amino acids and stop signals.