The Process of Replication of DNA l Genetics l NEET l NTA l NOTES

 

Overview

In eukaryotes, DNA replication occurs during the S phase of the cell cycle and involves several enzymes, with DNA-dependent DNA polymerase being the primary enzyme that catalyzes the polymerization of deoxynucleotides at a rate of approximately 2000 base pairs per second.

Key Points

• Energy-Intensive Process: Deoxyribonucleoside triphosphates serve two purposes:
• As substrates for the replication process.
• Providing energy from the two terminal phosphates.
• Initiation: DNA strands separate at a specific point called the origin of replication. Since the entire length cannot separate at once, replication begins at small openings called replication forks, forming a Y-shaped structure.
• Direction of Polymerization: DNA polymerase catalyzes the addition of nucleotides only in the 5’-3’ direction.
• On the template strand with 3’-5’ polarity, DNA synthesis is continuous.
• On the template strand with 5’-3’ polarity, DNA synthesis is discontinuous, producing short DNA fragments.
• Joining Fragments: The short, discontinuously synthesized DNA fragments are later joined by the enzyme DNA ligase.

Additional Enzymes

Several other enzymes play crucial roles in DNA replication:

• Helicase: Opens the DNA helix.
• Topoisomerase: Removes the supercoiling of DNA.
• Primase: Synthesizes RNA primers needed to start replication.
• Telomerase: Synthesizes the DNA at the telomeric ends of chromosomes.

By understanding these key points and the roles of various enzymes, the complex process of DNA replication in eukaryotes can be comprehensively grasped.

 

Replicating Fork

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