Final answer:
The enzymes helicase and DNA polymerase are primarily responsible for the work of replication, with helicase unwinding the DNA and DNA polymerase synthesizing new strands. DNA ligase then seals the new DNA fragments together.
Step-by-step explanation:
The two things that do the actual work of replication are enzymes known as helicase and DNA polymerase. Helicase unwinds the DNA double helix at the replication forks to make the DNA available as a template for copying. DNA polymerase then adds nucleotides to the 3'-ends of primers (which are initially placed by primase), effectively building a new DNA strand complementary to the template strand. Once the new DNA fragments are created, DNA ligase works to join the fragments together, sealing them into a continuous strand.
In summary, during the replication process, helicase unzips the DNA strand, and DNA polymerase synthesizes the new strands by adding nucleotides in a complementary fashion. This process ensures that the genetic information is accurately passed on to the daughter cells. As replication progresses, topoisomerase helps by preventing the DNA from becoming too tangled or supercoiled. These combined actions faithfully replicate the DNA, maintaining the genetic continuity essential for life's processes.