MCAT Biochemistry Question 105: Answer and Explanation
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Question: 105
15. Double-stranded RNA cannot be translated by the ribosome and is marked for degradation in the cell. Which of the following strands of RNA would prevent mature mRNA in the cytoplasm from being transcribed?
- A. Identical mRNA to the one produced
- B. Antisense mRNA to the one produced
- C. mRNA with thymine substituted for uracil
- D. Sense mRNA to the one produced
Correct Answer: B
Explanation:
The mRNA produced has the same structure as the sense strand of DNA (with uracils instead of thymines). Because bonding of nucleic acids is always complementary but antiparallel, the antisense strand of mRNA would be the one that binds to the produced mRNA, creating double-stranded RNA that is then degraded once found in the cytoplasm.