Final answer:
Nuclear splice sites in AU-AC introns are recognized during pre-mRNA splicing, enabling the removal of noncoding introns and the connection of exons to form functional mRNA. The spliceosome, with its corresponding recognition sequences, ensures accurate splicing. Mutations in these sequences or spliceosome components can disrupt protein synthesis.
Step-by-step explanation:
Nuclear splice sites are short sequences within AU-AC introns that are recognized by the spliceosome during pre-mRNA splicing. The spliceosome is a complex of proteins and RNA molecules, including small nuclear RNAs (snRNAs), which carries out the removal of introns from a pre-mRNA transcript. Introns are noncoding regions that must be excised to form a functional mRNA that consists solely of exons, the protein-coding regions. In introns, the beginning and end are marked by specific nucleotides: GU at the 5' end and AG at the 3' end. Additionally, editing changes in mRNA can result in various protein forms, such as the APOB protein in humans that has two forms due to a premature stop signal caused by mRNA editing.
Mutations in the spliceosome recognition sequences at each end of an intron or in the spliceosome components can have profound effects on the splicing process and, consequently, on protein synthesis. Such mutations may generate new spliceosome recognition sites or delete existing ones, potentially leading to defective splicing and dysfunctional proteins.