Mechanism of DNA replication
The DNA replication process is very similar in both prokaryotic and eukaryotic organisms. The DNA double helix opens, separates and each strand acts as a template for the synthesis of the new strand with nitrogenous bases complementary to those of the original strand.
The main characteristics of DNA replication are the following:
During replication, the two strands of the DNA molecule separate. From a parental molecule, two identical daughter molecules are obtained, each with an old (parental) chain and a new one.
Starting from the origin of replication, the synthesis of the new chains is carried out in opposite directions. At the point of origin of replication (ORI) the chains separate, causing a replication bubble. The chains are separating, and a replication fork is formed in each chain that grows, in opposite directions.
The semi - batch replication of DNA is determined by:
- The two strands of DNA are antiparallel.
- DNA polymerase activity in the 5'→3' sense.
From the point of origin, in each replication fork, two chains are obtained:
- Leading chain (leader or conductor): It is synthesized continuously. It is the copy of the string 3'→5'. Starts from a small primer on RNA to which are added nucleotides 5'→3'.
- Delayed chain: It is the copy of the chain 5'→3'. It is synthesized in the opposite direction to the advance of the replication fork, using Okazaki fragments, DNA fragments that are synthesized from a primer RNA.