Final answer:
When the σ factor detaches from the RNA polymerase during bacterial transcription, it allows the polymerase to transition from initiation to elongation. Termination is signaled by either rho-dependent or rho-independent signals, leading to the disassociation of the polymerase from DNA and the release of mRNA.
Step-by-step explanation:
In bacterial transcription, when the σ factor detaches from the RNA polymerase, it signals the transition from the initiation phase to the elongation phase of transcription. The core enzyme continues without the σ factor, transcribing mRNA in the 5' to 3' direction. This dissociation permits the polymerase to move along the DNA template more efficiently. However, the topic in question is specifically about the end of transcription, known as termination.
During termination, bacterial RNA polymerase needs clear signals to disengage from the DNA template and release the new mRNA. There are two types of termination signals: rho-dependent and rho-independent. Rho-dependent termination involves a protein called rho, which tracks the mRNA and uses its helicase activity to release the mRNA from the DNA once the polymerase stalls at a run of G nucleotides. On the other hand, rho-independent termination involves the formation of a stable hairpin structure followed by a series of uracil bases, causing the polymerase to stall and disassociate naturally from the DNA.