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The Steps of PCR exam Flashcards

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The Steps of PCR exam
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  • Denaturation
    The first step of PCR where DNA is heated to approximately 95°C to break hydrogen bonds and form single strands.
  • What is the purpose of the annealing step in PCR?
    To allow DNA primers to bind to the single-stranded DNA at around 55°C.
  • Taq polymerase
    A thermostable DNA polymerase used in PCR that can withstand high temperatures and is active at 72°C.
  • What happens during the extension step of PCR?
    Taq polymerase extends the primers, synthesizing new DNA strands in the 5' to 3' direction at 72°C.
  • Annealing
    The second step of PCR where the temperature is lowered to around 55°C, allowing DNA primers to bind to single-stranded DNA.
  • Why is Taq polymerase used in PCR?
    Because it is thermostable and can withstand the high temperatures used in PCR without denaturing.
  • Extension
    The third step of PCR where Taq polymerase synthesizes new DNA strands at 72°C.
  • What is the temperature used during the denaturation step of PCR?
    Approximately 95°C.
  • What is the role of DNA primers in PCR?
    To bind to single-stranded DNA during the annealing step, providing a starting point for DNA synthesis.
  • What is the ideal temperature for Taq polymerase activity?
    72°C.
  • How many steps are there in each PCR cycle?
    Three steps: denaturation, annealing, and extension.
  • What is the result of one PCR cycle?
    Two identical copies of the original DNA.
  • Why is PCR considered a cyclical process?
    Because the three steps (denaturation, annealing, and extension) are repeated multiple times to amplify DNA.
  • What happens to the DNA strands during the denaturation step?
    The hydrogen bonds are broken, and the double-stranded DNA separates into single strands.
  • What is the significance of the 5' to 3' direction in PCR?
    DNA synthesis by Taq polymerase occurs in the 5' to 3' direction.
  • What components are required in the PCR mixture?
    Template DNA, PCR primers, Taq polymerase, and DNA nucleotides.
  • What is the function of Taq polymerase during the extension step?
    To incorporate DNA nucleotides and extend the DNA primers, creating new DNA strands.
  • What happens to the temperature during the annealing step?
    It is lowered to around 55°C.
  • How does PCR amplify DNA?
    By repeating the steps of denaturation, annealing, and extension, exponentially increasing the number of DNA copies.
  • What is the role of the template DNA in PCR?
    To serve as the original DNA sequence that will be amplified.
  • What is the temperature change sequence in a PCR cycle?
    95°C for denaturation, 55°C for annealing, and 72°C for extension.
  • Why is it important for Taq polymerase to be thermostable?
    So it can withstand the high temperatures used during the denaturation step without denaturing.
  • What is the outcome of the extension step in PCR?
    The synthesis of new DNA strands, resulting in two identical copies of the original DNA.
  • How does the annealing step facilitate DNA synthesis?
    By allowing DNA primers to bind to single-stranded DNA, providing a starting point for Taq polymerase.
  • What is the main purpose of PCR?
    To amplify a specific segment of DNA.
  • What happens to Taq polymerase at cooler temperatures?
    It remains inactive because the temperatures are too low for it to synthesize DNA.
  • What is the significance of the cyclical nature of PCR?
    It allows for exponential amplification of the target DNA.
  • What is the role of DNA nucleotides in PCR?
    To be incorporated into the new DNA strands during the extension step.
  • What is the final product of a PCR cycle?
    Two identical copies of the original DNA sequence.