Transcription and RNA Processing · Zoology

A mutation in the branch point adenine of an intron would most likely result in:

  1. Complete failure to initiate transcription upstream
  2. Defective lariat formation and splicing arrest
  3. Loss of the protective 5' cap structure
  4. Failure of RNA polymerase to reach the terminator
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Correct answer: Defective lariat formation and splicing arrest

The branch-point adenine provides the 2'-OH nucleophile for the first transesterification reaction of splicing. A mutation at this site prevents lariat formation, blocking the entire splicing pathway and leading to intron retention in the mature transcript.

Difficulty: Medium Question 15 of 20

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