Final answer:
Pol II, encoded by the polB gene, is a DNA repair enzyme with a molecular mass of 90 kDa. The σ factor confers specificity to transcription initiation in prokaryotic RNA polymerase. For DNA replication, the origin of replication is recognized by specific proteins, initiating the process.
Step-by-step explanation:
Pol II, encoded by the polB gene in bacteria such as E. coli, functions as a DNA repair enzyme and not the major enzyme for DNA synthesis. Its molecular mass is approximately 90 kDa, making it a relatively large protein. In E. coli, the core enzyme of prokaryotic RNA polymerase consists of the subunits α, α, β, and β', but it is the σ (sigma) factor that confers specificity to transcription initiation. This σ factor enables the RNA polymerase holoenzyme to bind to specific promoter regions on the DNA, allowing for the accurate beginning of transcription. DNA polymerase I, one of the three main types of DNA polymerases found in prokaryotes, is a multifunctional enzyme with a 5'→3' exonuclease activity and a Klenow fragment that possesses polymerization and proofreading activities. DNA replication begins at specific nucleotide sequences called origins of replication, which are recognized by certain proteins that initiate the replication process. One such protein is helicase, which unwinds the DNA at the origin.