Final answer:
The protein responsible for opening dsDNA at the oriC is helicase. It ensures the separation of DNA strands, with topoisomerase and single-stranded binding proteins aiding in the replication process. If helicase is mutated, replication can be impeded.
Step-by-step explanation:
The protein that opens dsDNA at the oriC by melting the two strands apart is helicase. This enzyme utilizes the energy from ATP hydrolysis to separate the DNA strands, allowing replication to begin. In the process of DNA replication, topoisomerase works to alleviate the pressure that builds up ahead of the replication fork by breaking and reforming the DNA's phosphate backbone. Single-stranded binding proteins bind to the separated strands to prevent them from re-annealing prematurely.
Other key players in the process of DNA replication include primase, which synthesizes an RNA primer used by DNA polymerase to initiate the synthesis of a new daughter strand. If helicase is not functioning properly or is mutated, it can prevent the DNA strands from separating at the onset of replication, hindering the entire process.