Final answer:
The replication fork is where DNA unwinding, strand separation, and synthesis occur, involving helicase, topoisomerase, single-strand binding proteins, primase, and DNA polymerase. A mutated helicase gene affects the initial unwinding of the DNA, impairing the initiation of replication.
Step-by-step explanation:
In the replication fork, a series of events are essential for the duplication of DNA. Initially, helicase plays a critical role by unwinding the DNA helix, creating replication forks extended bidirectionally. This unwinding also leads to supercoiling; hence topoisomerase acts ahead of the replication fork to relieve the pressure by breaking and reforming the DNA's phosphate backbone. Single-strand binding proteins stabilize the single-stranded DNA to prevent rewinding. To initiate DNA synthesis, primase lays down an RNA primer, which DNA polymerase III uses to add nucleotides to the new DNA strand. Continuous synthesis occurs on the leading strand while on the lagging strand, synthesis is discontinuous, producing Okazaki fragments. These fragments are later connected after replacing RNA primers with DNA nucleotides, and DNA ligase seals the nicks, resulting in a continuous DNA molecule.
If the gene for helicase is mutated, the initial separation of DNA strands at the beginning of replication would be affected. This means the initiation of replication cannot occur properly, as the two DNA strands would not be unwound for the subsequent steps to take place.