A tRNA molecule specialized for the transfer of the amino acid valine has the anticodon CAG. Which codon on mRNA will it pair with?

A tRNA molecule specialized for the transfer of the amino acid valine has the anticodon CAG. Which codon on mRNA will it pair with?

• A. CAG
• B. GAC
• C. GCA
• D. GUC

Answer: (D)

tRNA recognizes mRNA codons through base pairing that runs antiparallel and is complementary. An anticodon of CAG will pair with a codon where each position matches C-G, A-U, and G-C in the opposite orientation. That makes the corresponding mRNA codon GUC when read 5' to 3'. This codon GUC is one of the valine codons, so the tRNA carrying valine with anticodon CAG pairs with it. The other options would require non-complementary pairings, so they wouldn’t be recognized by this tRNA.

tRNA recognizes mRNA codons through base pairing that runs antiparallel and is complementary. An anticodon of CAG will pair with a codon where each position matches C-G, A-U, and G-C in the opposite orientation. That makes the corresponding mRNA codon GUC when read 5' to 3'. This codon GUC is one of the valine codons, so the tRNA carrying valine with anticodon CAG pairs with it. The other options would require non-complementary pairings, so they wouldn’t be recognized by this tRNA.