Enzymes & Functions (DNA REPLICATION)

Untwist the (parental) DNA double helix at the replication forks, separating the two parental DNA strands and making them available as template strands.

• DNA polymerase I

• DNA polymerase III

• Topoisomerase

• Helicase

Synthesized RNA primer by adding RNA nucleotides that is complementary to the DNA template from 5’ to 3’

• DNA polymerase I

• Primase

• Topoisomerase

• Helicase

Relieves overwinding strain (ahead of replication fork) by breaking, swiveling, and rejoining DNA strands.

• DNA polymerase I

• Primase

• Topoisomerase

• Helicase

Bind to the unpaired DNA strands, keeping them from re-pairing.

• DNA polymerase III

• Primase

• Topoisomerase

• Single-strand binding proteins

Remove RNA nucleotides of RNA primer from 5’ end and replace with DNA nucleotides added one by one (to the 3’ end of pre-existing DNA strand).

• DNA polymerase I

• Primase

• DNA ligase

• Single-strand binding proteins

Catalyze the synthesis of new DNA strand by adding DNA nucleotides to the 3′ end of RNA primer or pre-existing DNA strand using parental DNA strand as a template.

• DNA polymerase I

• DNA polymerase III

• Helicase

• Single-strand binding proteins

Catalyze the synthesis of phosphodiester bond to join the sugar-phosphate backbones of Okazaki fragments into a continuous DNA strand.

• Topoisomerase

• DNA ligase

• Helicase

• DNA polymerase I