What is the function of a transcription factor?

• A. Enzymes that synthesize RNA.
• B. Transcription factors bind DNA at regulatory elements to control transcription, either activating or repressing.
• C. Proteins that unwind DNA during replication.
• D. RNA molecules that enhance translation.

Answer: (B)

Transcription factors regulate gene expression by binding to specific DNA sequences in regulatory regions such as promoters and enhancers. This binding helps recruit or block RNA polymerase II and other coactivators or corepressors, so the gene’s transcription is either turned on or off. They act as activators or repressors and can be modulated by cellular signals like hormones or phosphorylation, giving precise control over when a gene is expressed.

This isn’t about making RNA themselves—that’s the job of RNA polymerase. It isn’t about unwinding DNA during replication—that task belongs to helicases. And it isn’t about RNA molecules that boost translation—that’s a different layer of gene expression control, separate from transcription initiation.