Final answer:
Helicase is the protein or complex that moves ahead of the DNA polymerase during replication.
Step-by-step explanation:
The protein or complex that leaves the origin and moves ahead of the DNA polymerase during replication is Helicase.
Helicase separates the DNA strands at the origin of replication, allowing for the formation of replication forks. These replication forks are where DNA polymerase synthesizes new DNA strands.
Single-strand binding proteins and DNA gyrase are also involved in the replication process, but they do not move ahead of the DNA polymerase like helicase does.