Question

Which of the following statements is correct?
(i) RNA polymerase I transcribes rRNAs
(ii) RNA polymerase II transcribes snRNAs
(iii) RNA polymerase III transcribes hnRNA
(iv) RNA polymerase II transcribes hnRNA

A. (i) and (ii)
B. (i) and (iii)
C. (i), (ii) and (iv)
D. (i) and (iv)

Answer 1

Hint: All the types of RNA polymerase transcribes different RNAs. One of the types of RNA polymerase transcribes hnRNAs be it I, II or III.

Complete answer:
Transcription is the process by which the information stored in the strand of DNA gets copied into a new molecule of mRNA which is messenger RNA. It is the first step of DNA based gene expression where a particular segment of DNA is copied into RNA which is done with the help of RNA polymerase. Both the nucleic acids use base pairs of nucleotides as the complementary language.

In eukaryotes, transcription is achieved by the different types of RNA polymerase which are RNA polymerase I, II and III. All these contain different subunits and the classes of RNA too.
- RNA poly I transcribes the rRNAs which is ribosomal RNA
- RNA poly II transcribes ribosomes where hnRNAs are formed which is heterogeneous nuclear RNAs
- RNA poly III transcribes snRNA which is small nuclear RNAs

> If we look at the statement (i), it says RNA poly I transcribes rRNA and from the above explanation it is clear that this statement is correct which is (i)

> Now the statement (ii) says that RNA poly II transcribes snRNAs but in actual as per the explanation given above it transcribes hnRNAs. So statement (ii) is incorrect.

> Statement (iii) says that RNA poly III transcribes hnRNAs but it transcribes snRNAs and therefore this statement (iii) is also incorrect.

> Statement (iv) says that RNA poly II transcribes hnRNAs and this statement is the correct one as it transcribes hnRNAs.

Hence, The correct answer is option (D).

Note: As per all the types of RNA polymerase and which RNA it transcribes only the statement (i) and (iv) is the correct one. If you know about all the types of polymerase and their transcription then you can easily crack this question and you can't go wrong in any RNA polymerase related question.