Dna polymerase

Definition

DNA polymerase is an enzyme responsible for synthesizing new DNA strands by adding nucleotides complementary to a template strand during DNA replication. This enzyme plays a crucial role in ensuring the accuracy of DNA duplication and is essential for cell division and genetic stability.

5 Must Know Facts For Your Next Test

1. DNA polymerase can only add nucleotides to an existing strand of DNA; it cannot initiate synthesis on its own, which is why it requires an RNA primer from primase.
2. There are several types of DNA polymerases, with DNA polymerase I and DNA polymerase III being the most significant in prokaryotic cells for replication and repair.
3. In eukaryotic cells, there are multiple DNA polymerases (e.g., α, δ, ε), each having specialized functions such as leading strand synthesis and lagging strand synthesis.
4. DNA polymerase possesses proofreading activity, allowing it to correct errors by removing mismatched nucleotides, which increases the fidelity of DNA replication.
5. The rate of DNA synthesis by DNA polymerase is relatively fast, occurring at approximately 1000 nucleotides per second in bacteria.

Review Questions

• How does the function of DNA polymerase relate to the process of DNA replication?
  • DNA polymerase is essential for DNA replication as it synthesizes new strands by adding nucleotides to a template strand. It works at the replication fork, where the double helix is unwound, ensuring that each new strand is complementary to the original template. This function is critical for accurately duplicating the genetic material before cell division.
• Discuss the different types of DNA polymerases found in eukaryotic cells and their specific roles in DNA replication.
  • Eukaryotic cells have several types of DNA polymerases, including polymerase α, δ, and ε. Polymerase α initiates synthesis by laying down an RNA primer along with a few nucleotides. Polymerase δ primarily synthesizes the lagging strand and has proofreading capabilities to correct errors. Polymerase ε is involved in synthesizing the leading strand and also contributes to repair processes. Each type plays a unique role in ensuring accurate and efficient replication.
• Evaluate the significance of proofreading by DNA polymerase in maintaining genetic integrity during replication.
  • The proofreading ability of DNA polymerase is crucial for maintaining genetic integrity during DNA replication. By recognizing and correcting mismatched nucleotides through its 3' to 5' exonuclease activity, it significantly reduces the error rate during DNA synthesis. This function helps prevent mutations that could lead to genetic disorders or cancer, thus ensuring that the genetic information is accurately passed on during cell division.

Related terms

Nucleotide: The building blocks of DNA and RNA, composed of a sugar, a phosphate group, and a nitrogenous base.

Replication Fork: The Y-shaped region where the DNA double helix is unwound, allowing DNA polymerase to synthesize new strands during replication.

Primase: An enzyme that synthesizes a short RNA primer to provide a starting point for DNA polymerase during DNA replication.