Apentix/AP Biology/Unit 6: Gene Expression and Regulation/Question
AP Biologymediummcq1 pt

A point mutation changes the conserved GU dinucleotide at the 5' end of an intron in a human gene. What is the most likely effect on mRNA produced from this mutant allele?

A.Exons are removed instead of introns, leaving a short but fully functional polypeptide
B.Transcription halts because RNA polymerase cannot read past the mutated boundary
C.Splicing may be disrupted, causing intron retention or use of an alternative splice site and potentially altering the protein
D.The transcript loses its cap and tail, so it degrades immediately in the nucleus

Explanation

Core Concept

The conserved GU at a 5′ splice site helps the spliceosome recognize an intron boundary. Mutating it can disrupt normal splicing, but the exact outcome can vary: an intron may be retained, a cryptic splice site may be used, or exon recognition may change. Some outcomes alter the reading frame or introduce a premature stop, but a frameshift is not guaranteed.

Correct Answer

CSplicing may be disrupted, causing intron retention or use of an alternative splice site and potentially altering the protein

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