Step 5 of DNA Replication: Termination, Disassembly, and Repair for Intact and Ready-to-Use DNA

Step 5 of DNA replication

Step 5 of DNA replication is called termination

Step 5 of DNA replication is called termination. It occurs after the synthesis of the new DNA strands is complete. In this step, the replication machinery and the newly formed DNA molecules are disassembled and the process is finalized.

During replication, two DNA strands are unwound from each other at the origin of replication. The DNA polymerase enzyme moves along each template strand in opposite directions, synthesizing new DNA strands in a process known as leading and lagging strand synthesis.

In leading strand synthesis, DNA polymerase continuously adds nucleotides in the 5′ to 3′ direction, synthesizing the new DNA strand in the same direction as the replication fork movement.

In lagging strand synthesis, DNA polymerase synthesizes short DNA fragments called Okazaki fragments in the opposite direction of the replication fork movement. These fragments are later joined together by another enzyme called DNA ligase to form a continuous strand.

Once all the DNA has been replicated, the replication machinery needs to be removed from the DNA molecule. This process begins with the dissociation of the DNA polymerase from the template strands.

Next, the RNA primers that were originally used to initiate DNA synthesis on the lagging strand are removed by an enzyme called RNAse H. RNAse H degrades the RNA primers, leaving gaps in the DNA molecule.

The final step in replication termination is the repair of these gaps. The enzyme DNA polymerase fills in the gaps by adding the correct nucleotides, using the complementary DNA strand as a template.

Finally, the enzyme DNA ligase seals these gaps by catalyzing the formation of phosphodiester bonds between adjacent nucleotides, thus completing the replication process.

In summary, step 5 of DNA replication involves the disassembly of the replication machinery, removal of RNA primers, repair of gaps, and sealing of the DNA molecule, ensuring that the newly replicated DNA is intact and ready for use in cellular processes.

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