Question

What is RNA? Explain different types of non-genetic RNA with diagrams and functions.

Answer 1

Hint: These are non-genetic materials but always synthesized from genetic material DNA, but they play an important role in gene expression and also in the synthesis of protein.

Correct step by step answer:
The term RNA stands for ribonucleic acid. It is made up of ribonucleotides which consist of the ribose sugar, phosphoric acid, and nitrogenous bases. Non-genetic RNA does not act as genetic materials and is always synthesized from the DNA.
There are three types of non-genetic RNA:
- messenger RNA (mRNA)
- transfer RNA (tRNA)
- ribosomal RNA (rRNA)
1) Messenger RNA (mRNA):
The mRNA carries the coded information (genetic code) from DNA to ribosomes for the synthesis of polypeptides. Therefore, it is named messenger RNA and constitutes about 5- 10% of total cellular RNA. It is most heterogeneous in size and stability. This form of RNA is encoded by the DNA and contains codons for proteins.
2) Transfer RNA (tRNA):
The tRNA is also known as soluble RNA (sRNA) or adaptor RNA. It is the smallest known RNA species that constitute about 10-15 % of the total cellular RNAs. There are at least 20 types of tRNA molecules in every cell, one corresponding to each of the 20 amino acids required for protein synthesis. This RNA carries the specific amino acid as per the codon on the mRNA during protein synthesis.
3) Ribosomal RNA (rRNA):
The RNA which is found in ribosomes is called ribosomal RNA. It is most abundant and constitutes about 80% of the total cellular RNA. The rRNA molecule is highly coiled. In combination with proteins, it forms small and large subunits of the ribosomes, hence its name rRNA.

Note:
- RNA is a polynucleotide molecule.
- Adenine, guanine, cytosine, and uracil are the nitrogenous bases in the ribonucleotides.
RNA is a predominantly single-stranded nucleic acid. However, it may fold back on itself to form an antiparallel duplex structure called a hairpin which consists of a base-paired stem (like A-DNA) and a loop of unpaired bases.