Final answer:
TFIIH is a transcription factor that functions to unwind the DNA duplex during the formation of the transcription initiation complex, aiding in the preparation for RNA synthesis by RNA polymerase II. The correct option is d. a and b
Step-by-step explanation:
The function of TFIIH in the transcription initiation complex is unwinding the DNA duplex to allow transcription to occur. TFIIH is one of several transcription factors that assemble on the DNA template in a systematic fashion, stabilizing the preinitiation complex and assisting in the recruitment of RNA polymerase II.
Specifically, within the promoter region of a gene, upstream of the transcriptional start site, the TATA box is a key regulatory sequence. The binding of transcription factor TFIID to the TATA box recruits other factors, such as TFIIB, TFIIE, TFIIF, and TFIIH.
TFIIH has helicase activity that unwinds the DNA, creating a transcription bubble where the RNA polymerase can begin synthesizing RNA. Importantly, the question does not describe TFIIH as being involved in directly binding the TATA box or catalyzing RNA synthesis, which are functions of other parts of the transcription machinery. The correct option is d. a and b