🔬biological chemistry i review

key term - Primase

Definition

Primase is an enzyme that synthesizes short RNA primers during DNA replication, which serve as starting points for DNA polymerases to begin DNA synthesis. This enzyme plays a crucial role in the replication process because DNA polymerases cannot initiate synthesis on their own; they can only add nucleotides to an existing strand. By providing these RNA primers, primase ensures that the replication machinery can effectively copy the DNA.

5 Must Know Facts For Your Next Test

  1. Primase synthesizes RNA primers approximately 5-10 nucleotides long, which are essential for initiating DNA replication.
  2. The RNA primers produced by primase are later removed and replaced with DNA nucleotides by DNA polymerases.
  3. Primase works on both leading and lagging strands during DNA replication but is especially important for creating primers on the lagging strand.
  4. In bacteria, primase is often referred to as DnaG, while in eukaryotes, it is part of a larger complex with other proteins.
  5. The activity of primase is tightly regulated to ensure that primers are synthesized at the appropriate time and location during DNA replication.

Review Questions

  • How does primase contribute to the overall efficiency of DNA replication?
    • Primase contributes to the efficiency of DNA replication by synthesizing short RNA primers, which provide necessary starting points for DNA polymerases to add nucleotides. Without these primers, DNA polymerases would not be able to initiate the synthesis of new strands. This function is crucial for both leading and lagging strands, especially since the lagging strand requires multiple primers for the discontinuous synthesis of Okazaki fragments.
  • Compare and contrast the roles of primase and DNA polymerase in DNA replication.
    • Primase and DNA polymerase serve distinct but complementary roles in DNA replication. Primase synthesizes short RNA primers that are essential for starting the replication process, while DNA polymerase is responsible for extending those primers by adding DNA nucleotides to create new strands. Primase cannot synthesize long stretches of DNA, while DNA polymerase can only add nucleotides to an existing strand, thus relying on primase's action to initiate synthesis.
  • Evaluate the importance of primase in ensuring fidelity and accuracy during DNA replication.
    • Primase plays a vital role in ensuring fidelity and accuracy during DNA replication by setting the stage for precise nucleotide addition by DNA polymerases. The RNA primers created by primase must be correctly positioned to ensure that the resulting new DNA strands complement the original template accurately. If primase were not functioning correctly or if errors occurred during primer synthesis, it could lead to mismatches or incomplete replication, potentially causing mutations or genomic instability.