NEET 2026
- Exam
- NEET
- Year
- 2026
- Subject
- Biology
- Chapter
- Chapter
NEET 2026 · Biology · Chapter
In eukaryotes, the primary transcript that acts as a precursor of...
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?
Options
- ARNA polymerase I
- BRNA polymerase II
- CRNA polymerase III
- DPolynucleotide phosphorylase
Correct answer
B. RNA polymerase II
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 polymerase II
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 polymerase II