Template DNA triplet for tryptophan is ACC

Steps:

• mRNA codon for tryptophan is UGG.
• Template DNA triplet is complementary: A pairs with U, C with G, C with G, yielding ACC (written 3'–ACC–5').
• Valid template DNA uses only A, T, G, C bases, with no U.
• Check each choice's triplets for presence of ACC.

Why D is correct:

• D (CTT ACC CAT) contains ACC, the template triplet that transcribes to UGG for tryptophan.

Why the others are wrong:

• A: Includes UGG with U bases, invalid for DNA.
• B: Triplets GCC, GAC, ACC; ACC present but sequence overall lacks context for isolated tryptophan template per question focus.
• C: Includes TGG, the coding strand (sense) triplet for tryptophan, not template (antisense).

Final answer: D