Transcription and Translation · USMLE Step 1

During eukaryotic mRNA processing, what modification is added to the 5′ end of the nascent transcript soon after initiation?

  1. 3' poly-adenosine tail addition
  2. 7-methylguanosine cap
  3. Free 5' triphosphate group
  4. 3' polyuridine tract segment
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Correct answer: 7-methylguanosine cap

Eukaryotic pre-mRNA is capped at its 5′ end with a 7-methylguanosine cap shortly after transcription begins. This protects the mRNA and helps in its processing and transport.

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