The role of enzymes in the DNA replication process is to catalyze and coordinate the steps necessary for accurate and efficient duplication of the genetic material. Key enzymes involved include:
- DNA helicase : Unwinds and separates the double-stranded DNA by breaking hydrogen bonds between base pairs, creating single-stranded templates and replication forks
- RNA primase : Synthesizes short RNA primers on the leading and lagging strands, providing starting points with free 3′ hydroxyl groups for DNA polymerase to begin DNA synthesis
- DNA polymerase : Adds nucleotides to the 3′ end of the RNA primer, synthesizing the new complementary DNA strand in the 5′ to 3′ direction. It also proofreads and corrects errors to maintain fidelity
- DNA ligase : Joins Okazaki fragments on the lagging strand by forming phosphodiester bonds, resulting in a continuous DNA strand
- Topoisomerase (including DNA gyrase) : Relieves torsional strain and supercoiling ahead of the replication fork by making transient cuts in the DNA strands and rejoining them, facilitating smooth unwinding by helicase
- Single-strand binding proteins (SSB) : Bind to single-stranded DNA to prevent re-annealing and protect the strands from degradation, stabilizing the replication fork
Together, these enzymes form a coordinated molecular machine (the replisome) that ensures DNA strands are unwound, primed, copied, and rejoined accurately and efficiently during replication
. Each enzyme plays a specialized role in maintaining the integrity and continuity of the genetic information as cells divide.
