Final answer:
The sigma factor recognizes the promoter region of a gene and is crucial for the initiation of transcription in prokaryotes. It is not involved in the termination of replication, the formation of mRNA, or forming an open complex by itself; rather, it is part of the RNA polymerase holoenzyme that forms the open complex.
Step-by-step explanation:
The correct statement regarding sigma factor is that it recognizes the promoter region. Sigma factor is a protein component of the bacterial RNA polymerase that is necessary for the initiation of transcription. In the presence of sigma factor, the RNA polymerase holoenzyme can accurately recognize and bind to specific sequences at gene promoters, which are known as promoter sequences. Once bound, the transcription initiation complex forms, and transcription begins. This process is particularly important in prokaryotes, such as E. coli, to ensure that only the intended genes are transcribed, rather than random sections of the genome.
Therefore, the sigma factor is involved neither in the termination of replication nor does it form mRNA. Instead, sigma factor plays a crucial role in the formation of the open complex at the promoter region at the start of transcription.