How is DNA replicated?

At the beginning of replication, DNA molecules first use the energy provided by cells to untie two spiral double strands under the action of helicase. This process is called unwinding. Then, using each untied mother chain as a template and four kinds of deoxynucleotides in the surrounding environment as raw materials, under the action of DNA polymerase, according to the principle of base pairing and complementary pairing, a sub-chain complementary to the mother chain was synthesized respectively. With the unwinding process, the newly synthesized sub-chains are also extended, and each sub-chain and its parent chain are coiled into a double helix structure, thus forming new DNA molecules.

1.unwinding of DNA double helix

In the process of DNA replication, double-stranded DNA is first untied to form replication fork, which is a complex process involving many protein and enzymes.

①DNA melting enzyme

② Single strand DNA binding protein

③DNA topoisomerase

2.2 startup. DNA replication

All DNA replication starts from a fixed starting point.

3. Extension of replication

In the process of replication and extension, leading strand and subsequent chains are synthesized simultaneously. Leading strand continued to synthesize, and the subunit of the whole enzyme heterodimer combined with the leading strand template. On the basis of primer RNA synthesis, new DNA is continuously synthesized, and its synthesis direction is consistent with that of replication fork.

Then, with the synthesis of the chain, the intermediate Okazaki fragment is formed, and then connected into a continuous and complete new DNA chain through the valence of * * * *. It is divided into four steps:

4. Termination of copying

5.DNA polymerase