Question

How do mRNA, tRNA, and ribosomes, help in the process of translation?

Answer 1

Translation is a process in which genetic information contained within the order of nucleotides in messenger RNA is interpreted to generate the linear sequences of amino acids in proteins. This process mainly involves the translocation of the ribosome on the mRNA, translating it with the help of tRNA that reads the mRNA and facilitates step by step addition of amino acids.

Complete answer:
The process of translation involves three steps:

1. Activation of amino acids: In the presence of enzyme aminoacyl-tRNA synthetase, amino acids are activated by binding them with ATP, resulting in the formation of adenylated amino acid.
2. Charging of tRNA: Synthetase-bound adenylated amino acid reacts with tRNA to form aminoacylated tRNA, which is often referred to as charged tRNA.
3. Formation of polypeptide chain:

Chain initiation: It requires 3 initiation factors in prokaryotes and 9 initiation factors in eukaryotes.
- Binding of mRNA with the smaller subunit of ribosomes
- Binding of the 30S –mRNA with tRNAMeth, non-formylated methionine is attached with tRNA in eukaryotes and formylated in prokaryotes.
- Attachment of larger subunit of the ribosome. It is 50S in prokaryotes and 60S in eukaryotes.

Chain elongation: After the formation of the complete ribosome- mRNA-tRNA complex, an aminoacyl acceptor site (A-site) is established next to the P-site. It exposes the mRNA codon next to the initiation codon. tRNA corresponding to the respective codons are bound to this site and the proximity of these two charged tRNAs lead to the formation of a peptide bond and are energetically favored.

Chain termination: It is facilitated by the three stop codons, UAA, UGA, and UAG.

Note: mRNAs having multiple ORFs are referred to as Polycistronic mRNAs and those containing single ORF are called Monocistronic mRNAs. The secondary and tertiary structure of tRNA has been depicted by the Clover-leaf model and Inverted L-shaped model respectively.