Which statement describes replication initiation in bacteria such as Escherichia coli?

• A. DnaA initiates replication while DnaB and DnaG unwind and prime the DNA.
• B. DnaA, DnaB, and DnaG are eukaryotic replication factors.
• C. DnaA for initiation, DnaB helicase, and DnaG primase are used in bacteria like E. coli.
• D. DnaA is the helicase that loads primers.

Answer: (C)

Replication initiation in bacteria begins when the initiator protein DnaA binds to the origin of replication, oriC, at multiple DnaA boxes and, using ATP, oligomerizes to open up the AT-rich region. That opening allows the helicase to be loaded onto the DNA by DnaC, bringing DnaB to the site where it unwinds the DNA ahead of the replication fork. The primase DnaG then lays down short RNA primers on the exposed strands, providing starting points for DNA polymerase III to begin synthesis. This combination—DnaA driving initiation, DnaB serving as the helicase, and DnaG providing primers—is the standard setup for starting replication in bacteria like E. coli. The other descriptions mix up roles (DnaA is not the helicase; DnaG is not the primer loader) or refer to eukaryotic factors, which do not apply to bacterial replication initiation.