What is the role of transcription factors in gene expression?

What is the role of transcription factors in gene expression?

• A. They unwind DNA during replication.
• B. They degrade mRNA after transcription.
• C. They synthesize proteins directly.
• D. They bind to DNA and act as switches to control gene expression.

Answer: (D)

Transcription factors regulate gene expression by binding to specific DNA sequences near genes and acting as switches that decide whether transcription will occur. These proteins can recruit RNA polymerase II and other transcriptional machinery to the promoter or enhancer, enhancing transcription, or they can obstruct access and repress transcription. They respond to cellular signals, allowing genes to be turned on or off as needed. The other ideas mix up different cellular processes: unwinding DNA during replication is done by helicase, not transcription factors; degrading mRNA after transcription is the job of RNases; and synthesizing proteins directly is carried out by ribosomes during translation.

Transcription factors regulate gene expression by binding to specific DNA sequences near genes and acting as switches that decide whether transcription will occur. These proteins can recruit RNA polymerase II and other transcriptional machinery to the promoter or enhancer, enhancing transcription, or they can obstruct access and repress transcription. They respond to cellular signals, allowing genes to be turned on or off as needed.

The other ideas mix up different cellular processes: unwinding DNA during replication is done by helicase, not transcription factors; degrading mRNA after transcription is the job of RNases; and synthesizing proteins directly is carried out by ribosomes during translation.