Final answer:
RNA editing is specified by guide RNAs, which interact with the pre-mRNA transcript and cause modifications to the nucleotide sequence of the edited RNA molecule.
Step-by-step explanation:
RNA editing involves modifications to the sequence of nucleotides found in an edited RNA molecule. The modified sequence is specified by guide RNAs, which interact with the pre-mRNA transcript through complementary base pairing. The guide RNA contains more A nucleotides than the pre-mRNA has U nucleotides, and in regions where there is no complementary binding, the guide RNA loops out. The 3' ends of guide RNAs have a long poly-U tail, and these U bases are inserted in regions of the pre-mRNA transcript where the guide RNAs are looped.
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