A Level Biology Practice Exam

Which enzyme catalyzes the formation of phosphodiester bonds in RNA?

1. DNA polymerase

2. RNA polymerase

3. Ligase

4. Helicase

The correct answer is: RNA polymerase

The correct answer is RNA polymerase because this enzyme plays a crucial role in the synthesis of RNA during the process of transcription. RNA polymerase catalyzes the formation of phosphodiester bonds between ribonucleotides, linking them together to form a growing RNA strand. This enzymatic activity is essential for transcribing genetic information from DNA to RNA, allowing for the subsequent translation into proteins. DNA polymerase is responsible for synthesizing DNA, not RNA, by forming phosphodiester bonds between deoxyribonucleotides during DNA replication. Ligase functions in sealing breaks in the DNA backbone, particularly during DNA replication and repair, and does not address RNA synthesis. Helicase unwinds the DNA double helix, which is necessary for replication and transcription, but it does not catalyze the formation of phosphodiester bonds. Thus, RNA polymerase is uniquely involved in creating phosphodiester bonds specifically in the context of RNA synthesis.