Question

In mammalian cells, rRNA is produced in
a. Nucleus
b. Ribosome
c. Nucleolus
d. Golgi bodies

Answer 1

rRNA stands for Ribosomal RNA. It forms the key component of the cell organelles known as ribosomes. rRNA is synthesised in a dense part of the cell that contains rRNA encoding genes. Two subunits of rRNA, i.e. large and small make up one ribosome. rRNAs help in the process of translation, i.e. conversion of mRNA to proteins.

Complete answer:
• In mammalian cells, rRNA is produced in the nucleolus.
• The nucleolus is a dense structure that is present in the nucleus of a cell. It is found in eukaryotic cells and is the site for rRNA synthesis. Certain genes present in the nucleolus code for rRNA.
• Ribosomal RNA is a molecule that forms a major component of ribosomes, cell organelles that are responsible for synthesising proteins by translation.
• The rRNA molecules produced in the nucleolus are of different sizes. They are categorised into large and small. Ribosomes are made up of two subunits. Small rRNA combines with the ribosomal proteins to form the small subunit and large rRNA combines with the ribosomal proteins to form the large subunit. These two subunits form the entire ribosome.
• rRNAs form an association with messenger RNA and transfer RNA and ensure that the sequences get translated correctly into the corresponding proteins.

Hence, the correct answer is option (C).

Note: During translation, Ribosomal RNA is required at all the steps – initiation, elongation, and termination. This molecule ensures the proper bonding and alignment of other components like mRNA and tRNA during translation. They also possess the enzyme peptidyl transferase that catalyses the formation of bonds between amino acids during protein synthesis.