A Levels Biology (9700)•9700/13/O/N/20
Explanation
tRNA Anticodon to DNA Template Strand Complementarity
Steps:
- tRNA anticodon UAC base-pairs with mRNA codon via A-U, U-A, G-C, C-G rules, yielding mRNA codon AUG.
- mRNA codon AUG is transcribed from the DNA template strand.
- DNA template strand is complementary to mRNA: A pairs with T, U with A, G with C.
- Thus, complementary DNA sequence to AUG is TAC.
Why C is correct:
- TAC is the DNA template strand sequence, as it directly base-pairs with mRNA codon AUG per Watson-Crick rules.
Why the others are wrong:
- A. ATG is the DNA coding strand, which matches mRNA (with T for U), not the template.
- B. AUG is the mRNA codon itself, not a DNA sequence.
- D. TUG contains U, invalid in DNA (which uses T instead).
Final answer: C
Topic: Protein synthesis
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