Overview Function replicate cell genome in a manner that is highly accurate Process DNA melted to expose single strand to expose origin of replication single stranded binding proteins (SSBs) bind and stabilize melted DNA RNA primer added in 5' → 3' direction by primase DNA polymerase adds adds nucleotides in a 5' → 3' DNA polymerase III in prokaryotes DNA polymerase α and δ in eukaryotes can edit mistakes with a 3' → 5' exonuclease activity adds continuously on the leading strand adds discontinuous Okazaki fragments on the lagging strand because it must synthesize in a 5' → 3' direction DNA gyrase (topoisomerase II) breaks the DNA to prevent coiling RNA primer removed by RNAase H in eukaryotes and filled by a DNA polymerase by DNA polymerase I in prokaryotes and can fill simultaneously DNA ligase seals the nick between fragments Differences between prokaryotes eukaryotes prokaryotes single origin of replication eukaryotes multiple origins of replication Clinical importance antibiotics quinolones, fluoroquinolones block bacterial topoisomerase used to treat aerobic gram negatives in UTIs and gonorrhea e.g. drugs ending in -floxacin cancer chemotherapy etoposide, teniposide block eukaryotic topoisomerase