Final answer:
During promoter clearance in prokaryotic transcription, the σ subunit dissociates from the core enzyme of RNA polymerase after initiating transcription. This allows the core enzyme to continue with the elongation phase of synthesizing mRNA.
Step-by-step explanation:
During promoter clearance, the σ subunit disassociates from the core enzyme of prokaryotic RNA polymerase. The σ subunit is responsible for recognizing the promoter regions and is crucial to the initiation of transcription. Once transcription has been initiated and the RNA polymerase has synthesized a short stretch of RNA, the σ subunit dissociates from the polymerase.
This dissociation allows the core enzyme to proceed along the DNA template during the elongation phase of transcription, synthesizing mRNA at a steady pace. The core enzyme's ability to move forward without the σ subunit emphasizes how promoter clearance is a critical step in the process of transcription and subsequent gene expression.
Understanding the function of the σ subunit and its role in promoter clearance provides insight into the complex regulation of gene expression, a subject that continues to fascinate scientists studying the evolution of promoters and their role in higher organisms. The efficiency of promoter clearance and the precision of initiation and elongation processes are essential for the proper expression of genes and the overall functioning of a cell.