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Describe and explain how the polymerase chain reaction (PCR) is used to amplify a DNA fragment - AQA - A-Level Biology - Question 8 - 2021 - Paper 1
Question 8
Describe and explain how the polymerase chain reaction (PCR) is used to amplify a DNA fragment. Figure 9 shows the number of DNA molecules produced using a PCR. Ex... show full transcript
Worked Solution & Example Answer:Describe and explain how the polymerase chain reaction (PCR) is used to amplify a DNA fragment - AQA - A-Level Biology - Question 8 - 2021 - Paper 1
Step 1
Explain the shape of the curve in Figure 9.
Answer
The curve in Figure 9 exhibits an initial low plateau followed by an exponential increase.
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Initial Phase: At the start, the number of DNA molecules is low, as the amplification has just begun, and only a few cycles have occurred.
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Exponential Growth: As the PCR progresses, the number of DNA molecules doubles with each cycle, resulting in an exponential increase.
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Plateau Phase: Eventually, the curve plateaus as there are no more available primers or nucleotides, indicating that the reaction has reached its maximum output, and the enzyme (polymerase) may denature, further limiting amplification.