Stages of Protein Synthesis : Transcription and Translation
What is Transcription?
It is the process of formation of mRNA from a DNA template.
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.