11.2 DNA Replication

DNA pol I

Exonuclease activity removes RNA primer and replaces it with newly synthesized DNA

DNA pol III

Main enzyme that adds nucleotides in the 5’ to 3’ direction

Helicase

Opens the DNA helix by breaking hydrogen bonds between the nitrogenous bases

 Ligase

Seals the gaps between the Okazaki fragments on the lagging strand to create one continuous DNA strand

 Primase

 Synthesizes RNA primers needed to start replication

Single-stranded binding proteins

Bind to single-stranded DNA to prevent hydrogen bonding between DNA strands, reforming double-stranded DNA

Sliding clamp

Helps hold DNA pol III in place when nucleotides are being added

 Topoisomerase II (DNA gyrase)

Relaxes supercoiled chromosome to make DNA more accessible for the initiation of replication; helps relieve the stress on DNA when unwinding, by causing breaks and then resealing the DNA

Topoisomerase IV

Introduces single-stranded break into concatenated chromosomes to release them from each other, and then reseals the DNA