A codon is defined as which of the following?

A codon is defined as which of the following?

• A. A single nucleotide that pairs with an anticodon.
• B. A pair of nucleotides in mRNA.
• C. A triplet in DNA that signals replication.
• D. A three-nucleotide sequence in mRNA that codes for an amino acid.

Answer: (D)

A codon is a three-nucleotide sequence in mRNA that codes for an amino acid. During translation, the ribosome reads these three-base units in the mRNA, and each codon specifies which amino acid will be added to the growing protein. The tRNA molecules bring the corresponding amino acids and have anticodons that pair with the codons to ensure the correct amino acid is incorporated. This is why a single nucleotide isn’t enough to specify an amino acid, and a pair of nucleotides isn’t a codon. Codons are not in DNA and do not signal replication, since replication-related signals occur in DNA rather than in the mRNA used for protein synthesis.

A codon is a three-nucleotide sequence in mRNA that codes for an amino acid. During translation, the ribosome reads these three-base units in the mRNA, and each codon specifies which amino acid will be added to the growing protein. The tRNA molecules bring the corresponding amino acids and have anticodons that pair with the codons to ensure the correct amino acid is incorporated. This is why a single nucleotide isn’t enough to specify an amino acid, and a pair of nucleotides isn’t a codon. Codons are not in DNA and do not signal replication, since replication-related signals occur in DNA rather than in the mRNA used for protein synthesis.