What is a transcription factor and what is its general role?

• A. A transcription factor is a protein that binds RNA to enhance translation.
• B. A transcription factor is an RNA sequence that helps splicing.
• C. A transcription factor is a protein that binds DNA to regulate transcription, either promoting or repressing RNA polymerase recruitment.
• D. A transcription factor is a lipid that anchors transcription machinery to the membrane.

Answer: (C)

The main idea being tested is what transcription factors do and how they control gene expression. A transcription factor is a protein that binds to specific DNA sequences in promoters or enhancers and influences the start of transcription by RNA polymerase II. They can act as activators, helping recruit the transcription machinery, or as repressors, blocking access and reducing transcription. This binding and recruitment allow cells to turn genes on or off in response to signals, shaping when and where genes are expressed. The other options don’t fit because transcription factors do not bind RNA to enhance translation, do not directly participate in splicing of RNA sequences, and are not lipids that anchor machinery to membranes.