Final answer:
RNA processing includes the addition of a 5' methylguanosine cap, polyadenylation with a 3' poly-A tail, and the splicing of introns; however, the removal of exons is not part of RNA processing, making it the correct answer to the student's question.Removal of exons
Step-by-step explanation:
RNA processing does not involve the removal of exons; rather, it involves their splicing together after introns are removed. During RNA processing in eukaryotes, pre-mRNAs undergo several modifications, such as the addition of a 5' methylguanosine cap and a 3' poly-A tail, which protect the mRNA from degradation and assist in its export from the nucleus. This process also includes splicing, where introns (non-coding sequences) are excised and the remaining exons (coding sequences) are joined together.
Rarely, RNA editing may occur to insert missing bases after mRNA synthesis, which can change some of the nucleotides in mRNA, adding elements like a premature stop signal. However, this editing is distinct from the capping, polyadenylation, and splicing involved in RNA processing.