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Questions and Answers
During PCR, at which temperature does the annealing step typically occur, and what is its primary purpose?
During PCR, at which temperature does the annealing step typically occur, and what is its primary purpose?
- 72°C, to facilitate DNA polymerase adding nucleotides.
- 95°C, to separate the DNA strands.
- 55°C, to allow primers to attach to the DNA strands. (correct)
- 40°C, to initiate the cooling down process of the DNA sample.
How does Taq polymerase contribute to the efficiency of PCR, and from where is it derived?
How does Taq polymerase contribute to the efficiency of PCR, and from where is it derived?
- It withstands high temperatures; derived from _Thermus aquaticus_. (correct)
- It prevents primer dimers from forming; derived from mammals.
- It lowers the annealing temperature; derived from _E. coli_.
- It increases the rate of denaturation; derived from yeast.
If a scientist is using PCR to detect a specific viral infection, what is the primary goal of the PCR process in this scenario?
If a scientist is using PCR to detect a specific viral infection, what is the primary goal of the PCR process in this scenario?
- To amplify specific viral DNA sequences. (correct)
- To repair damaged host DNA caused by the virus.
- To directly kill the virus.
- To synthesize antibodies against the virus.
During PCR, which step involves breaking the hydrogen bonds between complementary base pairs?
During PCR, which step involves breaking the hydrogen bonds between complementary base pairs?
Flashcards
Polymerase Chain Reaction (PCR)
Polymerase Chain Reaction (PCR)
A technique that amplifies DNA fragments exponentially.
Denaturation
Denaturation
First step of PCR, where DNA strands separate at 95°C.
Taq Polymerase
Taq Polymerase
Heat-stable enzyme derived from Thermus aquaticus for DNA synthesis.
PCR Applications
PCR Applications
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Thermocycler
Thermocycler
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Study Notes
Polymerase Chain Reaction (PCR)
- PCR is a biomedical technology in molecular biology that amplifies DNA fragments to millions or billions of copies.
- PCR follows a geometric series (exponential growth) to increase the number of DNA copies.
- PCR uses three main steps to create copies: denaturation, annealing, and elongation.
- Denaturation occurs at 95°C, separating the two strands of DNA by breaking the hydrogen bonds between the complementary base pairs.
- Annealing occurs at 55°C, attaching short strands of nucleotides called primers to the DNA strands.
- Elongation occurs at 72°C, where DNA polymerase adds free nucleotides to the single-stranded DNA to form double-stranded DNA.
- This process is automated in a specialized machine called a thermocycler that repeats the three steps for about 30 cycles.
Taq Polymerase
- Taq polymerase is a DNA polymerase enzyme isolated from the bacterium Thermus aquaticus.
- Thermus aquaticus thrives in hot environments, such as hot springs, making its proteins, including Taq polymerase, very heat-stable.
- Taq polymerase can withstand temperatures up to 90°C for over 2 hours and works optimally at 80°C.
PCR Applications
- Tissue typing uses PCR to match potential organ donors with recipients.
- Oncogene detection uses PCR to analyze tumor genes and identify specific mutations for personalized cancer treatment.
- Detection of mutations can be used to detect mutations in embryos, through preimplantation genetic diagnosis (PGD), and in the fetal DNA circulating in pregnant mothers' blood.
- Viral and other infection identification uses PCR to amplify specific viral DNA sequences. The COVID-19 test is an example of PCR used for virus identification.
- Monitoring the spread of infectious diseases can be done by using PCR on samples from animal populations to identify viruses with the potential to cross over to humans.
- Forensic science utilizes PCR to amplify trace amounts of DNA from a crime scene, enabling DNA profiling.
- Research uses PCR as a core tool in various scientific fields, including biomedical research, synthetic biology, and genetic engineering.
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