Question

1. Explain the transcription and translation mechanism of protein and the role of GTP in translation process

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Answer 1

The central dogma of cell molecular biology is:

DNA to RNA to Proteins

DNA is formed by replication. DNA to RNA conversion is k/a transcription and finally RNA is translated to proteins.

Transcription: The three stages are Initiation, elongation and termination.

In this DNA is transcribed into pre-mRNA, which is then edited to prefer mRNA, which carries the information required for protein synthesis.

DNA is double stranded; out of which one strand (anti-sense) is transcribed to pre-mRNA, which is actually a copy of sense strand DNA. The direction of synthesis is 5’-3’. The transcription factors mediates the polymerase to initiate the transcription.

The pairing of NTPs is according to Watson and crick pairing with the help of enzyme RNA polymerase. The pairing continues until a triplet stop codon is formed. Then this pre-mRNA has some introns, which are spliced off k/a RNA splicing. Then a mature mRNA is ready to be translated into proteins. This mRNA is then transferred from nucleus to the ribosome, which is present on the mitochondria.

Translation: There are 4 phases of translation

1. Initiation: first t-RNA attaches to the mRNA

2. Elongation: The second t-RNA targets mRNA and then transfer of amino acid from first t-RNA to the second.

3. Translocation: the chain of amino acids is formed.

4. Termination: the stop codon releases the polypeptide from ribosomes.

m-RNA along with t-RNA forms a complex. M-RNA is codon while t-RNA is an anti-codon. The codon in mRNA interacts with the specific t-RNA to decode the mRNA codon. t-RNA at 3’ end has the corresponding amino acid attached.

The t-RNA picks the amino acid, which corresponds to the codon, and then delivers it to the ribosome.                

Role of GTP: At the initiation step GTP is required. The GTP hydrolysis to GDP. GTP catalyzes the molecular motion.

Also, it is required in the elongation phase for the binding of new amino acid in t-RNA to A-site of ribosome. Also required for the translocation of ribosome towards the m-RNA 3’end.