Final answer:
A mutation in the splicing sites (GU at 5'splice site, AG at 3'splice site) or in the branch point A can lead to incorrect splicing of pre-mRNA, potentially resulting in non-functional proteins due to the inclusion of introns or exclusion of exons in the final mRNA transcript.
Step-by-step explanation:
The question addresses the concept of splicing, which is the process of removing introns and reconnecting exons in a pre-mRNA molecule. Specifically, a mutation in the GU (5'splice site), AG (3'splice site) or A (in the branch point) are all critical regions in splicing and their mutation can prevent the correct splicing of pre-mRNA. During splicing, specific sequences are recognized and the intervening sequences (introns) are removed to produce a mature mRNA comprised only of exons, which can then be translated into functional proteins.
For instance, a transversion mutation in the GU-AG site can lead to the production of a non-functional protein. Mutations in splicing sites or the branch point can disrupt the normal removal of introns and can lead to the exclusion of necessary exons or inclusion of introns, resulting in abnormal proteins. This ultimately impairs the overall function of the enzyme or structural protein to be produced.