Types of RNA
RNA is of two types:
- Genetic RNA:
In plant , virus and Bacteriophage, RNA is the genetic material.
- Non-genetic RNA:
In organism where, DNA is the genetic material, RNA present in good quantity but
not act as a genetic material. The non-genetic RNA synthesized by DNA strand and is following types:
a) m-RNA: m-RNA is formed in nucleus with the help of DNA strand during the process called transcription. It contains and carry genetic information coded in DNA to the cytoplasm and finally attached to ribosome. It is small and short , live and comprise 5-10% of total RNA.
b) r-RNA : It is the most stable kind of RNA , comprise about 70-80% of total RNA. r-RNA is found in cytoplasm associate with ribosomal protein to form complete, functional ribosome and play an important role in protein synthesis. It is synthesized from the nucleus.
c) t-RNA: It is second most common RNA after r-RNA. It is also called soluble RNA made up of 75 nucleotides. It is smallest molecule of RNA and work as adapter molecules for carrying amino acids to the site of protein synthesis. It is synthesized in single stranded from but due to hydrogen bond, it changes into clobe leaf like structure and consists of 5 arms:-
I) Acceptor arm: It consists of seven base pair and four unpair nucleotide units. The four unpair nucleotide enclose a constant 3’-CCA sequence known as amino acid binding site and 5’end start to G(guanine).
ii) D arm: It consists of 15-18 nucleotides with 3-4 base pair in stem and 7-11 base pair are unpaired found in loop. It is synthetase binding site which recognize amino acid activating enzyme aminoacyl synthetase.
iii) Anticodon arm: It consist of 5 base pair and a anticodon loop have 7 unpaired nucleotide.
iv) T U C arm: It consists of 5 base pair and a loop have 7 unpaired nucleotides. It is ribosome recognition site.
v) Variable arm: This is an extra loop which is not a recognition site. It is variable according to the length of t-RNA.
