Final answer:
DNA replication is limited to the 5′-to-3′ direction due to the action of DNA polymerase. A hypothetical 3′-to-5′ replication process would cause significant problems, potentially resulting in increased mutations and challenges in maintaining the genome's integrity.
Step-by-step explanation:
DNA replication must occur in the 5′-to-3′ direction because DNA polymerase enzymes can only add nucleotides to the 3' end of a growing DNA strand. If replication were to occur in the 3′-to-5′ direction, crucial mechanisms of replication like continuous leading strand synthesis and lagging strand synthesis via Okazaki fragments would not be possible. In such a scenario, there would be significant issues with proofreading and the overall fidelity of DNA replication, likely leading to increased mutations and cellular dysfunction.
3'′-to-5'′ strand elongation would undermine the necessity for a primer with a free 3' hydroxyl group, potentially leading to incomplete DNA strands and errors in the genetic code. Since the antiparallel nature of DNA strands dictates the 5'-to-3' synthesis, a reversed direction would disrupt the coordinated replication process, complicating the synthesis of the complementary strands and affecting the cell's ability to accurately replicate its genome.