Question

Describe the function of mRNA, rRNA, and tRNA

Answer 1

Functions of mRNA, rRNA and tRNA:

DNA has the genetic information stored in it. This information has to be transcribed and translated for protein synthesis for the various functions to take place. These important functions are carried out by mRNA, rRNA and tRNA.

• The process of synthesis of mRNA from DNA is known as transcription.
• The process of protein synthesis from mRNA is known as translation.
• mRNA has the code for protein synthesis
• tRNA and rRNA plays a vital role in the synthesis of protein.

Functions of mRNA:

• The gene on the DNA is transcribed and mRNA is synthesised in the nucleus and it reaches the cytoplasm for the protein synthesis to take place.
• mRNA has the information on it, each 3 letter nucleotide code for one amino acid.
• There are 64 possible genetic codes that code for 20 amino acids.
• mRNA has AUG has the start codon for the protein synthesis to start at this site.
• mRNA has stop codon UGA, UAA, UAG where the protein synthesis is stopped and newly synthesised polypeptide is released.

Funtions of tRNA:

• tRNA has the complementary code for mRNA triplet codes on the folded structure of its anticodon loop.
• tRNA with the complementary code to mRNA brings the particular amino acid to rRNA A-site.
• Each amino acid has its own types of tRNA.
• Aminoacyl-tRNA synthetase enzyme link one amino acid to its particular tRNA forming aminoacyl-tRNA.
• Amino acids are attached at the amino acid acceptor stem of tRNA by covalent bond.

Ribosomal RNA (rRNA):

• RNA associates with proteins to form Ribosomes.
• It has the complex structure made of small subunit and large subunit.
• These ribosomes bind to the mRNA.
• Large subunit has A-site and P-site.
• It is at this A-site the tRNA brings the amino acid and attaches it.
• When ribosomes move one forward the amino acid at the A-site reaches the P-site, leaving A-site empty.
• tRNA brings a new amino acid based on the complementary mRNA code and attaches it to the A-site.
• Peptide bond is formed between the amino acids in the P-site and A-site.
• Further the rRNA moves forward, leaving the A-site empty again and the process is repeated.

Thus proteins are synthesised

It is called P-site because polypeptide chain is extended from that site, A-site because amino acid is attached at that site.

When rRNA reaches the stop site on the mRNA, rRNA small and large subunits separate from mRNA, which stops the protein synthesis and the newly synthesised polypeptide chain is released.

Thus mRNA, tRNA, and rRNA has important function in the process of protein synthesis.