DNA replication

helicase

breaks hydrogen bonds between nitrogenous bases, unwinding DNA double helix

• moves in both directions from origin of replication, forming a replication bubble with two replication forks at each end

origin of replication

specific DNA nucleotide sequence where DNA replication occurs, 1 in prokaryotes and thousands in eukaryotes

gyrase/topoisomerase

ahead of replication fork, relieves tension in DNA supercoil

single stranded binding proteins

hold DNA strands separate, stabilize unwound DNA

primase

adds RNA nucleotides to complementary base sequences, primer for DNA nucleotides as DNA polymerase can only add DNA nucleotides to another nucleotide

primers

short segments of RNA around 10 nucleotides long

DNA polymerase III

adds DNA nucleoside triphosphates to RNA primer sequence in a 5’ to 3’ direction on the daughter strand (reads template 3’ to 5’)

nucleosides

DNA bases with 3 inorganic phosphates, arrive with their own stored energy source needed to attach to DNA strand

DNA polymerase I

• removes RNA primers and replaces them with DNA nucleotides

• proofreading and correcting (repairing mismatched bases, removes abnormalities, etc.)

DNA ligase

joins okazaki fragments of lagging strand to form a single DNA strand