If the extension time is too long, secondary products can be formed, which can contribute to smearing. The quality of the template DNA can also affect the appearance of the PCR product on the gel. Degraded DNA can lead to the formation of shorter and larger fragments, which can contribute to smearing.
Generally, use an extension time of 1 min/kb. If the annealing time is too short, primers do not have enough time to bind to the template. Use an annealing time of at least 30 sec. If the annealing temperature is too high, primers are unable to bind to the template.
Primer length Longer primers are less efficient during the annealing step, resulting in a lower amount of PCR product.
Who can use a Motion to Continue or Extend Time? Anyone who needs to ask the court to continue (reschedule) a court date that has already been scheduled, or who needs more time to do something (like file an Answer or respond to a Motion another party has filed) can file a Motion to Continue or Extend Time.
The extension time of PCR depends upon the synthesis rate of DNA polymerase and the length of target DNA. The typical extension time for Taq DNA Polymerase is 1 min/kb, whereas that of Pfu DNA polymerase is 2 min/kb.
If the annealing temperature is too low, non-specific products can be generated, leading to smeared bands on the gel. If the extension time is too long, secondary products can be formed, which can contribute to smearing.
Many of the common problems with PCR and RT-PCR are identified during agarose gel electrophoresis of the reaction products. These include the absence of the expected amplification product, the presence of nonspecific products, excessive smearing, and the presence of a “primer dimer” band.
Excessive extension time can allow nonspecific amplification. Generally, use an extension time of 1 min/kb. Excessive annealing time may increase spurious priming. Use an annealing time of 30 sec.
Polymerase chain reaction (PCR) is a method widely used in molecular biology to make many copies of a specific DNA segment. Using PCR, a single copy (or more) of a DNA sequence is exponentially amplified to generate thousands to millions of more copies of that particular DNA segment.
A 1 min extension is typically sufficient to synthesize PCR fragments up to 2 kilobases (kb). To amplify larger fragments, the elongation step is extended at a rate of 1 min per kb. During the first extension, the template will not be length limiting and so templates will be synthesized that exceed the amplicon length.