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
• What is the role of DNA polymerase in proofreading during DNA replication?

  Checks and corrects mismatches
• During proofreading, DNA polymerase excises incorrect nucleotides and inserts the correct
• DNA polymerase reduces the error rate in DNA replication through proofreading.
• What is the 3' to 5' exonuclease activity of DNA polymerase?

  Removes incorrect nucleotides
• If DNA polymerase detects a mismatch, it pauses and excises the incorrect nucleotide.
• 3' to 5' exonuclease activity is a key component of proofreading.
• What action does DNA polymerase take when it encounters a guanine paired with a thymine?

  Removes thymine, inserts cytosine
• Match the feature with its description:

  Proofreading ↔️ Checks and corrects mismatches

  3' to 5' Exonuclease Activity ↔️ Removes incorrect nucleotides from 3' end

  Enzyme Involved ↔️ DNA polymerase

  Location ↔️ End of newly synthesized strand
• Proofreading reduces the error rate from 1 \in 10^{5}</latex> to $1 \in 10^{8}$ - $10^{10}$.higher
• Errors in DNA replication can lead to mutations and genetic disorders.
• How can errors in DNA replication contribute to cancer?

  Uncontrolled cell growth
• Overall accuracy in DNA replication can decline with age.
• Steps in the Mismatch Repair (MMR) pathway:

  1️⃣ MutS recognizes and binds to the mismatch

  2️⃣ MutL and MutH are recruited

  3️⃣ Mismatched strand is removed

  4️⃣ DNA polymerase and ligase fill the gap
• Which enzyme recognizes mismatches in the MMR pathway?

  MutS
• BER involves the creation of an apurinic/apyrimidinic (AP) site.