DNA Replication: Key Enzymes and Processes

Key Enzymes in DNA Replication

DNA Polymerase 3

• Catalyzes the addition of new nucleotides to the growing DNA strand.
• Functions only in the 5' to 3' direction.
  • Requires a 3' hydroxyl (OH) group for catalysis.

DNAG Primase

• Provides the essential 3' OH group for DNA Polymerase 3.
• Lays down an RNA primer (10-12 nucleotides long).
  • The primer is complementary to the DNA template.
  • Contains uridine instead of thymine, pairing with adenine (A).
• Does not require a primer to start synthesis.

Process Overview

• Leading Strand: Continuous replication process.
• Lagging Strand: Discontinuous replication (to be discussed further).

Nucleotides

• RNA vs. DNA Differences
  • In RNA, uridine is found instead of thymine.
  • Modified nucleotides such as GTP, GDP, GMP indicate RNA ribonucleotides.
  • DNA nucleotides are characterized by the presence of a deoxy group (e.g., GDTP).

Summary

• DNA Polymerase 3 requires a 3' OH group to begin nucleotide addition, provided by DNAG primase via an RNA primer.
• The replication process involves both continuous and discontinuous synthesis, corresponding to the leading and lagging DNA strands respectively.