Question

Which of the following RNA is short-lived?
A) tRNA
B) mRNA
C) rRNA
D) All of the above

Answer 1

Hint: Ribose nucleic acid (RNA) is a single strand or chain which is formed by the end to end polymerization of a number of ribonucleotides. RNA is involved in protein synthesis but in some viruses, it also serves as genetic material. There are two types of RNA – genetic RNA and non-genetic RNA.

Complete answer:
To answer this question we have to know about the non-genetic RNA in detail. It is present in all the cells, where DNA is the genetic material. These are of three types – ribosomal RNA (rRNA), transfer RNA (tRNA) and messenger RNA (mRNA).

A) tRNA – It is called transfer RNA, soluble RNA or sRNA. It constitutes about 15% of the total RNA. It is the smallest or short stable RNA consisting of 70-85 nucleotides. It acts as an adaptor molecule that is meant for transferring amino acids to the ribosome for the synthesis of the polypeptide.
B) mRNA – It is called messenger RNA. It constitutes 2-5% of the total RNA content of the cell. It carries genetic information from DNA for the formation of particular polypeptides. It is a short and unstable RNA. It is short-lived because it is only produced during protein synthesis and once the process completes it will degrade.
C) rRNA – It is called ribosomal RNA. It forms 70-80% of the total RNA content of the cell. It helps tRNA and mRNA in the synthesis of proteins over the ribosomes. It is a long and stable RNA.

So, the correct answer is option (B) mRNA.

Note: There are various functions of RNA –
- It is involved in the expression of the genetic code of DNA by forming specific proteins.
- It is genetic material in some viruses.
- It is a component of ribosomes, the site of protein synthesis.
- RNA primer is essential for DNA replication.