RNA polymerase needs a subunit to initiate transcription that is not needed for transcript elongation. What is the subunit? A) sigma B) Mg²⁺ C) rho D) the holoenzyme

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Sigma is a subunit of RNA polymerase that is responsible for recognizing specific DNA sequences and promoting the formation of the transcription initiation complex. Once transcription is initiated, sigma is no longer needed and can detach from the RNA polymerase complex. Therefore, sigma is only required for transcription initiation and not for elongation.

RNA Polymerase Needs a Subunit to Initiate Transcription That Is