Question

Which one of the following pairs of codons is correctly matched with their function or the signal for the particular amino acid?

• A. GUU, GCU - Alanine
• B. UAG, UGA - Stop
• C. AUG, ACG - Start/Methionine
• D. UUA, UCA - Leucine

Answer 1

Answer: (B)

UAG, UGA - Stop

Codons in option A codes for valine (GUU) and alanine (GCU). Alanine is coded by GCU, GCA, GCC, GCG. Codons in option B (UAG, UGA) do not code for any amino acid and thus cause termination of translation; hence called stop codons. Codons in option C code for methionine (AUG) and threonine. "AUG" also serves as start codon and encodes the first amino acid to be incorporated in any polypeptide of allorganisms. But ACG is not a start codon. Codons in option D codes for leucine (UUA) and serine (UCA). Correct answer is option B.