Which statement correctly describes DnaA in bacteria?

Which statement correctly describes DnaA in bacteria?

• A. It unwinds the DNA at the replication fork.
• B. It is the RNA primer synthesizing enzyme.
• C. It is the initiator protein that binds oriC to start replication.
• D. It seals nicks in the backbone after replication.

Answer: (C)

The key idea here is how bacterial DNA replication gets started. DnaA is the initiator protein that recognizes and binds to the origin of replication, oriC. It attaches at multiple specific sites there and forms an ATP‑bound oligomer, which induces a conformational change that melts the AT-rich region of oriC. This opening event is what sets the stage for the rest of replication, because it allows the helicase to be loaded (with its loader) and to begin unwinding the DNA to create the replication fork. So DnaA’s essential role is to bind oriC and start the replication process by promoting the initial opening of the origin. The other steps described by the other statements are carried out by different enzymes and do not define DnaA’s function: unwinding at the fork is done by the helicase, RNA primers are made by primase, and sealing nicks after replication is the job of DNA ligase.

The key idea here is how bacterial DNA replication gets started. DnaA is the initiator protein that recognizes and binds to the origin of replication, oriC. It attaches at multiple specific sites there and forms an ATP‑bound oligomer, which induces a conformational change that melts the AT-rich region of oriC. This opening event is what sets the stage for the rest of replication, because it allows the helicase to be loaded (with its loader) and to begin unwinding the DNA to create the replication fork. So DnaA’s essential role is to bind oriC and start the replication process by promoting the initial opening of the origin.

The other steps described by the other statements are carried out by different enzymes and do not define DnaA’s function: unwinding at the fork is done by the helicase, RNA primers are made by primase, and sealing nicks after replication is the job of DNA ligase.