Which statement best defines transcription factors?

• A. Proteins that bind to specific DNA sequences, thereby controlling the rate of transcription of genetic information from DNA to messenger RNA
• B. Enzymes that unwind DNA
• C. Molecules that degrade RNA
• D. Proteins that translate mRNA

Answer: (A)

Transcription factors are regulatory proteins that bind to specific DNA sequences near genes, and by doing so they regulate how often transcription is initiated from DNA to mRNA. By attaching to promoter or enhancer regions, they help recruit or block RNA polymerase II and the transcription machinery, which increases or decreases the transcription rate. They are not the enzymes that unwind DNA, not the ones that degrade RNA, and not the ones that translate mRNA. Some act as activators, others as repressors, and many work with coactivators or chromatin remodelers to make the gene accessible. This idea—binding DNA to control transcription rate—captures the essential role of transcription factors.