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A PCR machine is programmed to perform repeated thermal cycles with temperatures set sequentially at 94^ C , 54^ C , and 72^ C . Which of the following primary biochemical events occurs when the reaction mixture is held at 94^ C ?

Options

  1. ABinding of oligonucleotide primers to the template
  2. BSeparation of the double-stranded DNA into single strands
  3. CPolymerization of deoxynucleotides to synthesize a new strand
  4. DJoining of discontinuous DNA fragments by ligase

Correct answer

B. Separation of the double-stranded DNA into single strands

Step-by-step solution

A standard Polymerase Chain Reaction (PCR) cycle consists of three steps: denaturation, annealing, and extension. The highest temperature in the cycle, typically around 94^ C , is used for the denaturation step. At this temperature, the hydrogen bonds between the base pairs of the double-stranded template DNA break, resulting in the separation of the two strands. The temperature is then lowered to around 54^ C for the annealing of oligonucleotide primers, and subsequently raised to 72^ C for the extension step, whe

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