2.2.2 Accuracy and Proofreading

• What is the error rate during DNA replication without proofreading?

  $1 \in 10^{5}$
• DNA polymerase is responsible for proofreading during DNA replication.
• Proofreading occurs when DNA polymerase checks each newly added nucleotide against the template
• What is the error rate during DNA replication with proofreading?

  $1 \in 10^{8} to 10^{10}$
• DNA polymerase excises incorrect nucleotides during proofreading.
• What is the primary function of proofreading in DNA replication?

  Correct mismatched nucleotides
• Proofreading ensures the accuracy of genetic information during cell division
• The error rate during DNA replication is remarkably low due to proofreading.
• What is the role of DNA polymerase in proofreading?

  Checks for mismatched bases
• During proofreading, DNA polymerase excises incorrect nucleotides and inserts the correct
• Why is the accuracy of DNA replication critical?

  Maintains genetic information
• Steps involved in the proofreading process during DNA replication

  1️⃣ DNA polymerase checks newly added nucleotides

  2️⃣ A mismatch is detected

  3️⃣ DNA polymerase excises the incorrect nucleotide

  4️⃣ DNA polymerase inserts the correct nucleotide
• What is proofreading in DNA replication?

  Corrects mismatched nucleotides
• Proofreading during DNA replication is carried out by the enzyme DNA polymerase
• The error rate without proofreading is approximately 1 in $10^{5}$.
• What is the error rate with proofreading during DNA replication?

  1 in $10^{8}$ to $10^{10}$
• Proofreading ensures genetic information is maintained during cell division.
• Which key enzyme is involved in DNA proofreading?

  DNA polymerase
• The proofreading mechanism significantly reduces errors in DNA replication
• DNA polymerase uses 3' to 5' exonuclease activity to remove mismatched nucleotides.
• What is the first step in the proofreading process during DNA replication?

  Checking
• Errors in DNA replication can lead to mutations, which can cause genetic disorders
• The error rate of DNA replication with proofreading is 1 in $10^{8}$ to $10^{10}$ base pairs.
• What does DNA polymerase check during proofreading?

  Mismatched nucleotides
• DNA polymerase excises incorrect nucleotides and inserts the correct ones, reducing the error rate during DNA replication
• DNA polymerase checks each newly added nucleotide against the template strand to ensure correct base pairing
• DNA polymerase inserts the correct nucleotide after excising a mismatch during proofreading
• The 3' to 5' exonuclease activity of DNA polymerase reduces the error rate during DNA replication
• DNA polymerase corrects a guanine paired with a thymine by excising the thymine and inserting a cytosine
• Outline the steps involved in the proofreading process:

  1️⃣ Checking newly added nucleotides against the template strand

  2️⃣ Excision of incorrect nucleotides

  3️⃣ Insertion of correct nucleotides
• Errors in DNA replication can lead to mutations, which are changes in the DNA sequence
• Cancer can result from errors in DNA replication that trigger uncontrolled cell growth
• Match the DNA repair mechanism with its description:

  Mismatch Repair (MMR) ↔️ Corrects mismatched base pairs missed during replication

  Base Excision Repair (BER) ↔️ Repairs damaged bases by removing them from DNA
• In BER, DNA glycosylases create an apurinic/apyrimidinic (AP) site
• Proofreading occurs during DNA replication, while MMR and BER are post-replication processes
• The accuracy of DNA replication is essential for maintaining genetic stability