Learning Goal - DNA Replication - Functions of DNA primase, DNA polymerase I, DNA polymerase III and DNA ligase in replication

6 important questions on Learning Goal - DNA Replication - Functions of DNA primase, DNA polymerase I, DNA polymerase III and DNA ligase in replication

Explain the need for RNA primers in DNA replication.

RNA primers signal DNA polymerase 3 on where to add nucleotides, and also act as a starting point for the new strand, due to the limitation of DNA polymerase 3, where it can only add nucleotides to existing ones.

Compare the number of RNA primers on the leading and lagging strands.

There will only be one RNA primer attached to the leading strand, but multiple on the lagging strand that are placed at every replication bubble.

Outline the function of primase.

The role of primase is to synthesise RNA primers at the 5' end of the leading strand and at the 5' end of every Okazaki fragment in the lagging strand.
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Outline the function of DNA polymerase 3.

DNA polymerase 3 has two functions: one as an exonuclease, which proofreads the base sequence of the newly synthesised strand and corrects any mistakes to the sequence that may have been made, and secondly as a polymerase, which add new nucleotides to existing one to synthesise a new DNA strand.

Outline the function of DNA polymerase 1.

DNA polymerase 1 has two functions: one as an exonuclease, which removes the RNA primers attached to the newly synthesised strands, and as a polymerase, which adds new DNA bases to fill the gaps left by the RNA primers.

Outline the function of DNA ligase.

DNA ligase's role is to seal the gaps between the Okazaki fragments to completely form the lagging strand.

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