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.

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