Question

__________ functions in the expression of 18 and 28S ribosomal genes and is largely localized to the nucleolar region of the nucleus.

A) RNA polymerase II
B) RNA polymerase I
C) RNA polymerase III
D) Reverse transcriptase
E) RNA-dependent RNA polymerase

Answer 1

RNA polymerase I is responsible for the expression of 18S and 28S ribosomal genes and is primarily located in the nucleolar region of the nucleus, where it synthesizes rRNAs.

Step-by-step explanation:

RNA polymerase I (RNA polymerase I) functions in the expression of 18S and 28S ribosomal genes and is largely localized to the nucleolar region of the nucleus. RNA polymerase I is responsible for synthesizing all of the rRNAs, including 18S, 5.8S, and 28S, from the tandemly duplicated set of ribosomal genes.

In contrast, RNA polymerase II is responsible for transcribing the overwhelming majority of eukaryotic genes, synthesizing all protein-coding nuclear pre-mRNAs. RNA polymerase III transcribes a variety of structural RNAs that includes the 5S pre-rRNA, transfer pre-RNAs (pre-tRNAs), and small nuclear pre-RNAs.