Final answer:
T7 RNA polymerase does not require a sigma factor to initiate transcription. It has an intrinsic promoter recognition capability and directly binds to a hairpin-shaped promoter sequence in the DNA.
Step-by-step explanation:
No, T7 RNA polymerase does not require a sigma factor to initiate transcription. Unlike bacterial RNA polymerase that requires a sigma factor to recognize and bind to the promoter sequence, T7 RNA polymerase has an intrinsic promoter recognition capability in which it directly binds to a hairpin-shaped promoter sequence in the DNA.
The T7 RNA polymerase is from the T7 bacteriophage and is commonly used in research laboratories for in vitro transcription. It can synthesize large amounts of RNA within a short period of time.
To terminate transcription at the desired sequence, the template DNA must be cut (linearized) prior to RNA synthesis, causing the polymerase to fall off at the cut site and end transcription.