Observe the table and answer the given question:
How many codons with 'A' at second position code for amino acids?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 14
Codons with A at the second position are the 16 codons of the form N-A-N: UAU, UAC, UAA, UAG, CAU, CAC, CAA, CAG, AAU, AAC, AAA, AAG, GAU, GAC, GAA, GAG. Of these, UAA and UAG are stop codons, so 16 − 2 = 14 code for amino acids.
Option (1) 16 — Incorrect. 16 includes the two stop codons.
Option (2) 14 — Correct. In the codon table, the codons with A in the second position are those of the form NAN: 16 in all. Two of them, UAA and UAG, are stop codons, so 14 code for amino acids.