Question

Most abundant RNA of the cell
A) mRNA
B) tRNA
C) rRNA
D) None of the above

Answer 1

Hint: The two subunits of the main organelle involved in the translation process have their own sets of these types of RNAs.

Complete Answer:
- The ribosomes consist of two subunits, working together as translation sites, these ribosomes are formed due to the association of rRNAs with a set of proteins thus rRNAs are found in the ribosomes and hold 80% of the total RNA present in the cell.

Therefore the correct answer is C, i.e. the most abundant RNA present in the cell is rRNA.

- The two subunits of ribosomes are 50S (the large subunit) and a 30S (the small subunit), both of them have their own specific rRNA molecules.
- Different rRNAs present in the ribosomes include large rRNAs and small rRNAs, belonging to the 50S and 30S subunits of the ribosome, respectively.
- mRNA (messenger RNA) holding the genetic codes travel along this complex structure and associate with tRNA (transfer RNA) to carry out the process of translation, in which a long chain of amino acids get assembled resulting in a polypeptide chain.
- These polypeptide chains further fold into secondary, tertiary and quaternary structure to form a functional protein.

Additional information:
- Aminoacylated tRNA (transfer RNA) binds to the ribosome subunits, during the translation process, in a codon-dependent manner, to assemble the associated amino acid chains with the specific codon encoded by the mRNAs.
- 30S ribosomal subunit interacts with the anticodon arm of the tRNA, while 50S ribosomal subunit interacts with the acceptor arm. Non-aminoacylated tRNA floats in the cytoplasm in search of their codon-specific amino-acid molecule.
- mRNA associates with the 30S subunit of the ribosome to begin the protein synthesis process. Messenger RNA (mRNA) carries the genetic information from the cell nucleus, where it serves as a template for protein synthesis, and takes the information to ribosomes in the cytoplasm.
- After translation either the mRNA is stored for later translation or gets immediately degraded, but ultimately all the mRNA gets degraded.

Note: rRNA accounts for roughly 80% of the total RNAs in the cell, tRNA are 15 % and mRNA thus has only a small portion of the total RNA count.