Multiple Choice
Why is a DNA polymerase from a thermophilic bacterium used in PCR?
18. Biotechnology
The Steps of PCR
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PCR is known for its power of amplifying a target DNA sequence at a high speed. Each cycle can double the
number of DNA molecules (target sequence). Which of the following is CORRECT regarding PCR?
A
In order to make 10 copies of the DNA, you need at least 5 cycles of PCR.
B
Helicase is required in order to separate the two strands in PCR.
C
Dideoxynucleotides are used in PCR.
D
DNA primers are needed in PCR.
E
All of the above.
Verified step by step guidance1
Understand the basic concept of PCR (Polymerase Chain Reaction), which is a technique used to amplify a specific DNA segment. It involves repeated cycles of heating and cooling to denature DNA, anneal primers, and extend the DNA strand.
Recognize that each cycle of PCR doubles the amount of DNA. Therefore, to make 10 copies starting from a single DNA molecule, you need to calculate the number of cycles required using the formula: \(2^n = \text{number of copies}\), where \(n\) is the number of cycles.
Identify the components required for PCR: DNA template, DNA primers, DNA polymerase (usually Taq polymerase), nucleotides, and a buffer solution. Helicase is not required because the high temperature during the denaturation step separates the DNA strands.
Understand that dideoxynucleotides are not used in PCR. They are used in DNA sequencing methods like Sanger sequencing to terminate DNA strand elongation.
Conclude that DNA primers are essential for PCR. They bind to the target DNA sequence and provide a starting point for DNA synthesis by the DNA polymerase.
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The Steps of PCR practice set
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