Enzymes

DNA Replication Enzymes:

1. Helicase:

   • Role: Unwinds the DNA double helix, breaking the hydrogen bonds between the complementary bases to create the replication fork.

2. Single-Strand Binding Proteins (SSBs):

   • Role: Bind to the separated single DNA strands to prevent them from re-annealing or forming secondary structures.

3. Primase:

   • Role: Synthesizes short RNA primers that provide a starting point for DNA polymerase to begin DNA synthesis.

4. DNA Polymerase III:

   • Role: Adds nucleotides to the 3' end of the RNA primer and synthesizes the new DNA strand in the 5' to 3' direction.

5. DNA Polymerase I:

   • Role: Removes the RNA primers and replaces them with DNA nucleotides.

6. DNA Ligase:

   • Role: Seals the gaps between Okazaki fragments on the lagging strand by forming phosphodiester bonds, creating a continuous DNA strand.

7. Topoisomerase (e.g., DNA Gyrase):

   • Role: Relieves the tension and supercoiling in the DNA that occurs as a result of the unwinding by helicase.

8. Sliding Clamp:

   • Role: Helps hold DNA polymerase in place as it synthesizes new DNA, ensuring processivity during replication.

9. RNAse H:

   • Role: Removes RNA primers from the lagging strand.

Transcription Enzymes:

1. RNA Polymerase:

   • Role: Catalyzes the synthesis of RNA from a DNA template by adding ribonucleotides to the growing RNA strand in the 5' to 3' direction.

2. Helicase (transcription):

   • Role: Unwinds the DNA to allow the RNA polymerase to access the template strand.

3. Topoisomerase:

   • Role: Prevents supercoiling of DNA during transcription, similar to its function in replication.

4. Transcription Factors:

   • Role: Proteins that bind to specific DNA sequences to facilitate the binding of RNA polymerase to the promoter and the initiation of transcription.