Identify the correct stop codon.

The correct answer is Option (1) → UAG

Of the 64 codons of the genetic code, 61 code for amino acids. The other three, UAA, UAG and UGA, do not code for any amino acid. They are stop (terminator) codons, which end the making of a polypeptide during translation.

(1) UAG — Correct. UAG is one of the three stop codons.

(2) UUA — Incorrect. UUA codes for the amino acid leucine.

(3) UUC — Incorrect. UUC codes for phenylalanine.

(4) UUG — Incorrect. UUG also codes for leucine.

Note: A similar question was also asked in CUET (UG) 2023 on 22-06-2023 (Slot 3).

NCERT Extract:
Genetic Code – “… (i) The codon is triplet. 61 codons code for amino acids and 3 codons do not code for any amino acids, hence they function as stop codons.”
Genetic Code – “… (vi) UAA, UAG, UGA are stop terminator codons.”