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Stages of Protein Synthesis : Transcription and Translation

What is Transcription?

It is the process of formation of mRNA from a DNA template.

MECHANISM :

Transcription involves DNA Replication, through which mRNA is formed.

  •  Enzyme Helicase unwinds and unzips the two strands of DNA,by breaking the hydrogen bonds between the nitrogenous bases(purine and pyrimidine).
  • The exposed ends of the nucleotides represents the Replication fork.
  • SSBP (Single Strand Binding Protein) holds the two strands apart, thus prevents twisting of the strands.
  • DNA Polymerase III builds new DNA strand by adding nucleotide in 5' to 3' direction.
  • Since the direction of construction is from 5' to 3', the strand is called leading strand and is continous.
  • The lagging strand 3' to 5' direction is discontinous and the fragments are called Okazaki Fragments.
  • Enzyme Ligase connects/seals the Okazaki fragments, thus forming a continous strand.
  • Enzyme Primase synthesizes RNA primer at 5'.
  • DNA Polymerase I removes and replaces RNA Primer with DNA nucleotides.

 

Thus, mRNA is synthesized.

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