Enzyme Machinery and Process of DNA Replication
- The most important enzyme involved in DNA replication is the DNA polymerase. DNA replication is an energy dependent process.
- Replication begins on the specific site on the DNA, known as the origin of replication (ori).
- During the process of replication, the two DNA strands do not separate completely, the replication occurs within the small opening of the DNA helix known as a replication fork.
- At the origin, the Helicase enzyme starts unzipping and unwinds the DNA. The strands are thus separated. The Single-stranded binding proteins (SSBs) help in keeping the strands separated.
- Topoisomerase prevents the DNA from supercoiling and primase plays a role in making RNA primers on both the strands. It helps the DNA polymerase to identify where to start from.
- The DNA polymerase adds the nucleotides in 5′ to 3′ direction. Consequently, on the strand with polarity 3′-5′, the replication is continuous, while on the other strand with polarity 5′-3′, it is discontinuous.
- The strand with continuous replication is known as the leading strand whereas the one with discontinuous replication is known as the lagging strand.
- The enzyme DNA ligase later joins the discontinuously synthesized fragments, called Okazaki fragments.