In eukaryotes, the primary transcript that acts as a precursor of mRNA, known as heterogeneous nuclear RNA (hnRNA), is synthesized by which of the following enzymes?

Step-by-step solution

In eukaryotes, there are three major types of RNA polymerases in the nucleus: RNA polymerase I transcribes rRNAs (28S, 18S, and 5.8S). RNA polymerase II transcribes the precursor of mRNA, which is known as heterogeneous nuclear RNA (hnRNA). RNA polymerase III is responsible for the transcription of tRNA, 5S rRNA, and snRNAs (small nuclear RNAs). Polynucleotide phosphorylase is an enzyme that polymerizes ribonucleotides into RNA without a template. Therefore, hnRNA is synthesized by RNA polymerase II. Answer: RNA po