What is transcription initiation?

• A. RNA polymerase binds to the promoter region and unwinds DNA to start RNA synthesis.
• B. Ribosomes catalyze the synthesis of a new DNA strand.
• C. DNA polymerase binds to the terminator to end transcription.
• D. Messenger RNA is degraded before synthesis.

Answer: (A)

Transcription initiation is the stage where RNA polymerase first engages the DNA to begin making RNA. It starts when the enzyme binds to a promoter region, which provides the signal for where to start. After binding, the polymerase unwinds a short stretch of DNA to create an open complex, exposing the template strand so RNA synthesis can begin. The first ribonucleotide is then added, and transcription proceeds in the 5′ to 3′ direction.

This description matches the idea that initiation involves promoter binding, DNA unwinding, and start of RNA synthesis. The other options describe unrelated processes: translation by ribosomes, DNA replication by DNA polymerase, or RNA degradation, none of which correspond to how transcription starts.