Final answer:
DNA replication initiation requires helicase to separate the strands, topoisomerase to alleviate tension, single-strand binding proteins to stabilize the DNA, and primase to synthesize an RNA primer for DNA polymerase III to begin synthesis, including Okazaki fragments on the lagging strand.
Step-by-step explanation:
During the initiation of DNA replication, several enzymatic activities are required. The enzyme helicase is responsible for separating the DNA strands at the origin of replication. Topoisomerase then alleviates the tension ahead of the replication fork by breaking and reforming the phosphate backbone of the DNA. Single-strand binding proteins bind to the separated DNA strands to prevent them from re-annealing into a double helix.
After these steps, primase synthesizes a short RNA primer, which is necessary for DNA polymerase to begin the synthesis of the new DNA strand. Specifically, DNA polymerase III extends the RNA primer with new DNA nucleotides to synthesize the daughter DNA strand. On the leading strand, DNA synthesis occurs continuously, whereas on the lagging strand, synthesis occurs in short segments known as Okazaki fragments.
If helicase is mutated, DNA strands will not be separated at the beginning of replication, which is critical for replication to begin. Thus, helicase is essential to the initiation of DNA replication.