Final answer:
Splicing is a precision process involving spliceosomes, composed of snRNAs and proteins, which remove introns from pre-mRNA by recognizing splice sites through base-pairing, ensuring exact exon rejoining for functional protein synthesis.
Step-by-step explanation:
Pre-mRNA splicing is a critical process in gene expression and involves the removal of non-coding regions known as introns from the pre-mRNA transcript. This mechanism relies on complex structures called spliceosomes, which are constituted by proteins and small nuclear RNAs (snRNAs). The spliceosome uses base-pairing reactions to recognize the conserved sequences at the 5' and 3' splice sites of an intron.
The snRNAs within the spliceosome interact with these splice sites to bring the intron's ends close together. The snRNAs facilitate a series of base-pairing interactions that accurately align the splice sites for the cleaving of the intron and the subsequent ligation of the coding regions, or exons. An essential aspect of splicing is the precision of the process, as a mistake of even a single nucleotide can alter the reading frame and result in a dysfunctional protein.
During the splicing process, the snRNPs (small ribonuclear proteins) contained within the spliceosome specifically bind to the intron's splice sites, forming a loop, sometimes called a lariat, where the intron is excised. Following the removal of the intron, the exons are ligated to produce a mature mRNA, which is then exported to the cytoplasm for translation into a protein.