What are codons and anticodons and where do they function?

• A. Codons are on tRNA; anticodons are on mRNA; they function in translation.
• B. Codons are on DNA; anticodons are on tRNA; they function in translation.
• C. Codons are on mRNA; anticodons are on tRNA; they function at the ribosome during translation.
• D. Codons are on rRNA; anticodons are on DNA; they function in transcription.

Answer: (C)

Codons are three-nucleotide words on messenger RNA that specify which amino acid should be added next during protein synthesis. Anticodons are the complementary three-nucleotide sequences on transfer RNA, and each tRNA carries the specific amino acid for its anticodon. During translation, the ribosome brings mRNA and tRNA together and reads the codons; the anticodon on a charged tRNA pairs with its matching codon on the mRNA, and the amino acid is incorporated into the growing polypeptide chain. This all happens at the ribosome, in the cytoplasm or on the rough endoplasmic reticulum. So the correct view is that codons are on mRNA, anticodons are on tRNA, and they function at the ribosome during translation.