PCR Flashcards
PCR
Polymerase chain reaction.
Target Amplification
Making many copies of a specific DNA sequence.
Target (PCR)
A short region of DNA
Amplicons
Copies of DNA
Amplification Program
A specified number of cycles that are divided into steps during which the samples are help at a particular temperature for an amount of time.
Cycles (PCR)
One series of denaturation, annealing, and extension.
Annealing
Second step in PCR where two oligonucleotide primers prime the synthesis of DNA anneal to complementary sequences on the template.
Mispriming
Aberrant initiation of DNA synthesis from a primer hybridized to template sequences different from the intended target.
Primer Dimers
PCR products that are approximately double the size of the primers.
Taq Polymerase
Thermostable enzyme from the thermophillic bacterium Thermus aquaticus.
Tth Polymerase
Enzyme from Thermus thermophilis. Also has reverse transcription activity.
Stoffel Fragment
Modified version of the polymerase enzyme.
Real-time PCR
PCR performed in an instrument that can measure the formation of amplicons in real time. AKA Quantitative PCR. Will inform if the the target sequence is found.
Negative Template Control
A negative control with DNA that lacks the target sequence to ensure that the primers are not annealing to nontarget sequences of DNA.
False Negative
Amplification failure.
Psoralen
A substance from plants that covalently attaches to DNA (it attaches to the thymidines, uracils, and cytidines in the DNA chain) under UV light. Helps with the prevention of denaturation and amplification of treated DNA.
Hot-start PCR
Used to help prevent mispriming.
Three methods:
1. Mix reactions on ice and add to a preheated thermocycler.
2. Wax was used in older thermocyclers as a barrier to prevent evaporation.
3. Use of sequestered enzymes. These will not activate unless heated by the first denaturation step.
Touchdown PCR
A modification of the PCR program. Annealing temperatures begin with a higher than optimal temperature for target primer-binding. The annealing temperature is then lowered by 1 degree every cycle or every other cycle until the optimal temperature is reached.
Hybrid in PCR
DNA/RNA hybrid
Multiplex PCR
More than one primer is being used in PCR.