DNA Replication (MCB school revision)

Okazaki fragment - short fragment of DNA.

Helicase - separates the double strand.

Single-strand binding protein – prevents single strand coiling back to original shape.

DNA Polymerase synthesize only 5’ to 3’.

5’ to 3’ (direction of DNA polymerase) = Leading strand (3’ to 5’ old strand, 5’ to 3’ new strand, direction towards helicase)

5’ to 3’ (direction of DNA polymerase) = Lagging strand (5’ to 3’ old strand, 3’ to 5’ new strand, direction away from helicase)

Leading strand –

1) RNA Primase - attach a RNA Primer onto the strand
2) DNA Polymerase 3 - adds deoxyribonucleotides to synthesize the new complementary strands of DNA.

Lagging Strand –

1) RNA Primase – attaches a RNA Primer
2) DNA Polymerase III - adds deoxyribonucleotides
3) DNA Polymerase I – removes the RNA and replace it with DNA
4) DNA ligase – Forms phosphodiester bonds