DNA replication can be defined as a cellular process by which DNA makes a copy of itself during cell division. The cell must make a copy of itself before it gets divided into two so that after the division each cell will contain a complete complement of the genetic material. This replication occurs during the S phase of cell division. DNA replication has a self complementary nature. DNA is the genetic material that defines every cell. The first chemical that helps with the process is named as Helicase. It breaks the hydrogen bonds that hold the complementary bases of DNA together like A with T and C with G.
DNA Replication Process: –
- The initial step of DNA replication is called unzipping.
- It starts by the separation of the strands of DNA when the hydrogen bonds between the base pairs break down.
- This separation creates a ‘Y’ shape known as replication fork.
- In the next step, DNA strands unwind.
- These two separated strands will act as pattern for creating new DNA strands.
- The specific sites at which the DNA unwinding and initiation of replication take place are known as origin of replication.
- There may be thousands of origins of replication per chromosome.
- One strand is oriented towards the replication fork and known as leading strand. One is away from the replication fork and known as lagging strand.
- These two strands are replicated differently as their orientation is different.
- The replication of leading strand is continuous and of lagging strand is discontinuous.
- In lagging strands, there are chunks of DNA that are known as Okazaki fragments. These fragments will need to be joined up later.
- The new strand is proofread and after finding no mistakes in the new DNA sequence an enzyme called DNA ligase seals up the sequence.