1. Helicase:
* Function: Unwinds the DNA double helix, breaking the hydrogen bonds between the base pairs. This creates a replication fork, which is the Y-shaped region where replication occurs.
2. Single-Strand Binding Proteins (SSBs):
* Function: Bind to the separated single strands of DNA, preventing them from re-annealing (sticking back together). This keeps the strands open for replication.
3. DNA Primase:
* Function: Synthesizes short RNA primers (around 10 nucleotides long) that provide a starting point for DNA polymerase to begin replication. DNA polymerase can only add nucleotides to an existing chain, it cannot start a new one.
4. DNA Polymerase (multiple types):
* Function: The primary enzyme responsible for synthesizing new DNA strands.
* DNA Polymerase III (Prokaryotes) or DNA Polymerase δ (Eukaryotes): The main polymerase responsible for adding nucleotides to the new DNA strand. It reads the template strand and adds complementary nucleotides, ensuring accurate replication.
* DNA Polymerase I (Prokaryotes) or DNA Polymerase ε (Eukaryotes): Removes RNA primers and fills in the gaps with DNA nucleotides.
5. DNA Ligase:
* Function: Joins the Okazaki fragments (short DNA segments produced on the lagging strand) together, creating a continuous DNA strand.
6. Topoisomerases:
* Function: Relieve the torsional stress that builds up ahead of the replication fork as the DNA unwinds. They cut and rejoin DNA strands to prevent supercoiling.
Key Concepts:
* Leading Strand: Replicated continuously in the 5' to 3' direction.
* Lagging Strand: Replicated discontinuously in short fragments (Okazaki fragments) that are later joined together.
* Semiconservative Replication: Each new DNA molecule contains one original strand and one newly synthesized strand.
Let me know if you'd like a more in-depth explanation of any specific enzyme or process!
