Final answer:
The open section of DNA where replication occurs is called a replication fork, formed by the enzyme helicase during DNA replication.
Step-by-step explanation:
During DNA replication, an open section of DNA where a DNA polymerase can replicate is called a replication fork. The replication fork is formed when the enzyme helicase separates the DNA strands. Primers are then synthesized by primase, allowing DNA polymerase to start the synthesis of new DNA strands. On the leading strand, DNA is synthesized continuously, while on the lagging strand, it is synthesized in short stretches known as Okazaki fragments. These are eventually joined together to form a continuous strand once the RNA primers are replaced with DNA nucleotides by DNA polymerase I, and the gaps are sealed by DNA ligase.