Final answer:
The splicing reaction involves intron removal from the primary RNA transcript through a series of protein-mediated rearrangements.
Step-by-step explanation:
The splicing reaction involves a series of rearrangements called intron removal from the primary RNA transcript. This process is catalyzed by protein complexes called spliceosomes, which are composed of proteins and RNA molecules called snRNAs. The spliceosomes recognize specific sequences at the 5' and 3' ends of the intron, and they cut the intron out and splice the remaining exons together. This rearrangement allows the mRNA to be properly processed and translated into a functional protein.