You are studying the rRNA synthesis and processing in a mutant cell line. You find that these cells synthesize a correct precursor rRNA, but do not correctly process it into the expected 3 rRNAs that are found in normal cells. Which of the following organelles is likely to be missing or defective in these cells, thus accounting for the failed rRNA processing?
A) endoplasmic reticulum
B) Golgi complex
C) nuclear matrix
D) nucleolus
E) ribosome

Question

Quizplus · Accepted Answer

The nucleolus is responsible for the synthesis and processing of rRNA, so a defect or absence in the nucleolus would lead to improper rRNA processing.  During or immediately following transcription of pre-rRNA from rDNA in the nucleolus, the ribosomal RNA precursor (pre-rRNA) is modified and associates with a few ribosomal proteins. In order to generate the mature 18S, 5.8S, and 28S rRNAs from the precursor 45S rRNA, the precursor rRNA goes through a series of cleavages in order to remove the external and internal spacers.

You Are Studying the RRNA Synthesis and Processing in a Mutant