Initiating DNA replication involves specific proteins binding to a particular DNA sequence known as the replicator at the replication origin. The replicator serves as a regulatory element that influences the behavior of the chromosome where it is located. These proteins guarantee that DNA synthesis starts at the appropriate chromosomal site, following cues from the cell cycle. When the replicator and the replicon are on the same chromosome, this interaction is described as "acting in cis". On the other hand, the initiator is a protein that can be encoded on any chromosome within a cell. It operates "in trans" because it doesn't have to be located on the same chromosome as the replicon it regulates. The initiator binds to the origin which triggers the melting of DNA strands nearby creating an open complex. This complex allows other replication proteins like primase,helicase, and DNA polymerase to join and form the replisome, initiating DNA synthesis. Among the different initiator proteins, the DnaA protein in Escherichia coli is extensively studied and understood.