If a cell mistakenly transcribed and translated a gene's intron, the most likely outcome would be additional amino acids would be inserted into the chain.
Introns are non-coding regions of a gene that are typically removed during RNA processing, resulting in the formation of mature mRNA that is translated into a protein. If an intron were transcribed and translated, the resulting protein would likely contain a sequence of amino acids corresponding to the intron's nucleotides. This could lead to a dysfunctional protein due to the presence of non-standard sequences, as introns are not generally designed to code for functional protein sequences.
The other options you provided either describe effects that wouldn't occur or are not accurate:
- Errors in the protein would be repaired: While cells have mechanisms to correct mistakes during translation, a mistakenly generated protein containing an intron is unlikely to be recognized and repaired effectively.
- The DNA would remain the same as before: The DNA would indeed remain unchanged, but this is not a direct consequence of the transcription and translation of the intron.
- The intron would begin to duplicate itself: Introns do not duplicate themselves through this process; their transcription and translation would simply produce an aberrant protein.
Thus, the most fitting response to your question is the insertion of additional amino acids into the polypeptide chain.