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To produce a continuous DNA chain from the many DNA fragments made on the lagging strand, a special DNA repair system acts quickly to erase the old RNA primer and replace it with DNA. An enzyme called DNA ligase then joins the 3′ end of the new DNA fragment to the 5′ end of the previous one to complete the process (Figures 5-13 and 5-14).
DNA replication is called a semi-discontinuous process because while the leading strand is being synthesized continuously, the lagging strand is synthesized in fragments.
The other strand (in the 5' direction from the primer) is called the lagging strand, and replication along it is called discontinuous replication. The double helix has to unwind a bit before...
17 mar 2022 · As synthesis proceeds, an enzyme removes the RNA primer, which is then replaced with DNA nucleotides, and the gaps between fragments are sealed by an enzyme called DNA ligase. The process of DNA replication can be summarized as follows:
Unwinding of DNA at the origin and synthesis of new strands, accommodated by an enzyme known as helicase, results in replication forks growing bi-directionally from the origin. A number of proteins are associated with the replication fork to help in the initiation and continuation of DNA synthesis.
This behaviour where the leading strand is synthesized continuously and the lagging strand is synthesized discontinuously is called semi-discontinuous replication. Fig. 26.7. Continuous DNA replication on both strands initiated independently at the two ends (as observed in adenovirus).
As discussed in Chapter 3, DNA replication is a semiconservative process in which each parental strand serves as a template for the synthesis of a new complementary daughter strand. The central enzyme involved is DNA polymerase, which catalyzes the joining of deoxyribonucleoside 5′-triphosphates (dNTPs) to form the growing DNA chain.
