Question

Compare and contrast the accuracy of:

1. DNA replication
2. RNA synthesis
3. Protein synthesis

What mechanisms are used to ensure the fidelity of each of these processes? in writing no diagrams or pictures

Answer 1

DNA replication takes place in nucleus. RNA synthesis tales take place firstly in nucleus then in cytoplasm while protein synthesis takes place in the cytoplasm and on the ribososme.

In DNA synthesis DNA double helix act as a template and proofreading activity in DNA replication is done by exonuclease and enzyme DNA polymerase. The cell cycle check points can detect the various issues found on DNA and whenever there is an error the checkpoints get activated. Various proteins such as cdks (cyclin dependent kinases) helps to send signal for the arrestment of the cell cycle. Although DNA replication is not completely perfect but the accuracy is comparative higher than transcriptio.

In RNA synthesis genes in the genome acts as a template. Proofreading is done by the RNA polymerase and the chances of error is comparatively high. The fidelity of transcription is maintained by the the DNA-damage checkpoint kinases. It is tough to repair single stranded RNA if nucleotides are incorrectly incorporated. The RNA polymerase acts as the fidelity checkpoint to correct the RNA synthesis.

In protein synthesis the mRNA acts as a template and proofreading is done by the 3'-5' exonuclease activity. Translation process requires accurate amino acid selection along with the mRNA decoding on the ribososme. The fidelity check is done by an enzyme named aminoacyl-tRNA synthetase which catalyses the amino acid's attachment to their respective tRNA along with the hydrolysis of incorrect amino acid which has been activated.