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BIO NMDCAT Structure of DNA
nmdcat.online July 3, 2026

94. A point mutation occurs within the consensus sequence of a 5′ splice donor site of a crucial structural gene. During pre-mRNA processing, this molecular defect will most likely cause the spliceosome to

A. Skip the downstream exon entirely or retain the entire mutated intron
✓
B. Add an exceptionally long poly-A tail to the 5' end of the transcript
C. Convert the mature mRNA back into a double-stranded DNA template
D. Shift the promoter sequence into the coding exon

📝 Explanation

Mutilating a splice site prevents the spliceosome from recognizing the intron-exon boundary, leading to intron retention or exon skipping during splicing.

📖 Additional Information

  • Skip the downstream exon entirely or retain the entire mutated intron
  • Add an exceptionally long poly-A tail to the 5' end of the transcript
  • Convert the mature mRNA back into a double-stranded DNA template
  • Shift the promoter sequence into the coding exon

Mutilating a splice site prevents the spliceosome from recognizing the intron-exon boundary, leading to intron retention or exon skipping during splicing.

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