Final answer:
The events of DNA replication are initiated at sequences called origins. DNA replication involves the copying of DNA to create identical daughter molecules and begins at specific origins of replication. Transcription is the production of RNA from DNA, with the initiation stage involving the RNA polymerase's sigma subunit.
Step-by-step explanation:
The events of DNA replication are initiated at sequences called origins.
DNA replication is the process of copying parental DNA to create identical daughter DNA molecules. It starts at specific DNA sequences known as origins of replication, where initiator proteins, such as those in the bacteria E. coli, bind to begin the replication process. These origins are usually rich in adenine-thymine (AT) sequences due to their lower stability compared to cytosine-guanine (CG) sequences, making them easier to unwind.
In contrast, transcription is the process of creating an RNA copy of a specific DNA sequence. This is the step in gene expression where mRNA is synthesized as a transcript of the gene's DNA code. The stages of transcription include initiation, where the RNA polymerase binds to the promoter; elongation, where the RNA strand is extended; and termination, where the RNA polymerase detaches from the DNA once the RNA is synthesized.
Regarding the stage of bacterial transcription where the σ (sigma) subunit of RNA polymerase is involved, it plays a critical role in initiation. This subunit helps the core RNA polymerase enzyme recognize the promoter, facilitating the binding to the DNA, and thus beginning the process of transcription.