Final answer:
Exonuclease activity is important in DNA replication and repair, playing a role in removing RNA primers, proofreading DNA, and helping to splice introns during mRNA processing.
Step-by-step explanation:
Exonuclease activity is crucial in the process of DNA replication and repair. During DNA replication, it is responsible for the removal of RNA primers, which are initially placed to start the replication process. DNA polymerases have 3'-5' exonuclease activity, which is used to proofread the newly synthesized DNA strand.
This activity helps in correcting errors by removing mismatched nucleotides and replacing them with the correct ones. Additionally, exonucleases work in conjunction with other enzymes such as DNA ligase to ensure that the gaps between the Okazaki fragments on the lagging strand are sealed, resulting in a continuous DNA strand.
During the removal of group-I introns, a guanine nucleotide cofactor is necessary, which leads to splicing of the intron and joining of the exons. This process, along with 5' capping and polyadenylation, is essential to generate a translatable mRNA molecule.
Furthermore, errors in splicing mechanisms can lead to mutations that may result in nonfunctional proteins, which may be caused by disruptions in the recognition sequences at the ends of introns.