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View additional product information for TaqMan™ Fast Virus 1-Step Multiplex Master Mix for qPCR (No ROX) - FAQs (5555536, 5555534, 5555532)
24 product FAQs found
If you are targeting a low-abundance gene, you may have trouble getting Ct values in a good, reliable range (Ct > 32). To increase the sensitivity of the assay, you may want to consider the following:
- Increase the amount of RNA input into your reverse transcription reaction, if possible
- Increase the amount of cDNA in your qPCR reaction (20% by volume max)
- Try a different reverse transcription kit, such as our SuperScript VILO Master Mix, for the highest cDNA yield possible
- Consider trying a one-step or Cells-to-CT type workflow (depending on your sample type)
Most times your instrument software can automatically set a proper baseline for your data. Check out our short video, Understanding Baselines, for more information on how to set them (https://www.youtube.com/watch?feature=player_embedded&v=5BjFAJHW-bE).
In most cases your instrument software can automatically set a proper threshold for your data. Check out our short video, Understanding Thresholds, for more information on how to set them (https://www.youtube.com/watch?feature=player_embedded&v=H_xsuRQIM9M).
There could be several reasons for no amplification from an assay or primer set. Please see these examples and suggested solutions in our Real-Time Troubleshooting Tool (https://www.thermofisher.com/us/en/home/life-science/pcr/real-time-pcr/qpcr-education/real-time-pcr-troubleshooting-tool/gene-expression-quantitation-troubleshooting/no-amplification.html) for more details.
There could be several reasons for amplification in a NTC well. Please see these examples and suggested solutions in our Real-Time Troubleshooting Tool (https://www.thermofisher.com/us/en/home/life-science/pcr/real-time-pcr/qpcr-education/real-time-pcr-troubleshooting-tool/gene-expression-quantitation-troubleshooting/amplification-no-template-control.html) for more details.
There are several reasons that amplification could be delayed. Please see the information in our Real-Time Troubleshooting Tool (https://www.thermofisher.com/us/en/home/life-science/pcr/real-time-pcr/qpcr-education/real-time-pcr-troubleshooting-tool/gene-expression-quantitation-troubleshooting/abnormal-amplification-curves/amplification-occurs-later.html) for more details.
There are several reasons that amplification could be delayed. Please see the information in our Real-Time Troubleshooting Tool for more details (https://www.thermofisher.com/us/en/home/life-science/pcr/real-time-pcr/qpcr-education/real-time-pcr-troubleshooting-tool/gene-expression-quantitation-troubleshooting/abnormal-amplification-curves/amplification-occurs-later.html).
It may be possible to use your SYBR Green primers for a TaqMan assay, depending on how they were designed. You would have to design a separate probe to use with your existing primers. Please refer to the guidelines in this manual (https://tools.thermofisher.com/content/sfs/manuals/cms_041902.pdf) on “Manually Designing Primers and Probes” for the next steps. If you have Primer Express Software, you can use that software to design a probe. Please note that restricting the design using the predesigned SYBR primers may not allow for a successful probe design.
Comparative Ct experiments use an endogenous control gene to normalize the cDNA input. Please watch this short video (https://www.youtube.com/watch?feature=player_embedded&v=jst-3hD_xFQ) for more details on how this works. For a protocol workflow, please refer to our Guide to Performing Relative Quantitation of Gene Expression (https://tools.thermofisher.com/content/sfs/manuals/cms_042380.pdf).
In a relative quantification experiment, you will need to identify an endogenous control and a reference (or calibrator) sample. An endogenous control is a gene that does not change in expression across all the samples in your study. A reference sample is the sample that you are comparing all others to. This is often the untreated, or control, sample. Please see our Relative Gene Expression Workflow bulletin (https://tools.thermofisher.com/content/sfs/brochures/cms_075428.pdf) for more step-by-step guidelines on how to design your experiment.
In a standard curve experiment, you must generate a standard curve for each target gene. The standards should closely represent the sample (i.e., RNA for RNA input, plasmid or gDNA for DNA input). This reference (http://www.ncbi.nlm.nih.gov/pubmed/11013345) is a good review of standard curves and the experimental setup. You can also review this short video (https://www.youtube.com/watch?v=mE5ieko9_RQ) on standard curve experiments.
Absolute quantification will quantitate unknowns based on a known quantity. It involves the creation of a standard curve from a target of known quantity (i.e., copy number). Unknowns can then be compared to the standard curve and a value can be extrapolated. Absolute quantification is useful for quantitating copy number of a certain target in DNA or RNA samples. The result usually is a number followed by a unit, such as copy number and ng, etc.
Relative quantification can quantitate a fold difference between samples. It involves the comparison of one sample to another sample (calibrator) of significance. For example, in a drug treatment study you could compare a treated to an untreated sample. The quantity of the calibrator is not known and cannot be measured absolutely. Therefore the calibrator (untreated sample) and samples (treated samples) are normalized to an endogenous control (a gene that is consistently expressed among the samples) and then compared to each other to get a fold difference. Relative quantification is useful for quantitating messenger RNA levels. Since the result is a fold change or ratio, it is not followed by a unit.
The method that you choose will depend on the type of data you need from your experiment. You can find more information here (https://www.thermofisher.com/us/en/home/life-science/pcr/real-time-pcr/qpcr-education/absolute-vs-relative-quantification-for-qpcr.html) as well.
No. A TaqMan probe, once cleaved, cannot be re-quenched. Therefore a melt curve does not apply when using a TaqMan assay.
TaqMan and SYBR Green chemistries are two different methods of detection for qPCR. Please see this detailed comparison of these two approaches (https://www.thermofisher.com/us/en/home/life-science/pcr/real-time-pcr/qpcr-education/taqman-assays-vs-sybr-green-dye-for-qpcr.html). You can also watch this short video (https://www.youtube.com/watch?feature=player_embedded&v=fkUDu042xic) on how TaqMan assays work.
Please view this short video (https://www.youtube.com/watch?v=eIaPGhOjBQo), which explains some best practices for replicates and plate setup.
Check out this short video (https://www.youtube.com/watch?feature=player_embedded&v=4sXPUbIrh3A) to understand the different phases of the PCR reaction and why they are important.
One-step RT-PCR is convenient, and less prone to contamination as there is less opportunity for pipetting error. This method is also faster than two-step. However, the cDNA cannot be archived, and fewer genes can be analyzed. Two-step RT-PCR gives you the ability to archive cDNA, analyze multiple genes, and gives greater flexibility. This table (https://www.thermofisher.com/us/en/home/life-science/pcr/real-time-pcr/qpcr-education/1-step-vs-2-step.html) also provides a comparison.
Yes they can. However, it is important to recognize the true linearity and detection limits of your assay: Ct values above the cut-off can indicate non-specific amplification, unless your NTC is a true- no-target control, and you have run a statistically significant number of replicates. Any results with Ct above the recommended cut-off need to be validated with individual assays on plates.
The typical Ct cut-off on TaqMan Array Cards is 32, which is equivalent to Ct 35 on a plate (10 µl reaction). Previous studies show that if you use pre-amplification, a Ct cut-off of 29 or 30 can be used to reduce numbers of false positives (see Technical Note Optimized protocols for human or rodent microRNA profiling with precious samples). To ensure that you have selected a correct cut-off, you should run replicates of the same sample and use Ct cut-off before you see an increase in the Standard Deviation.
TaqMan Fast Universal PCR Master Mix is recommended for two-step RT-PCR, but for one-step reactions, we recommend using TaqMan Fast Virus 1-Step Master Mix as the preferred reagent.
Most likely there was amplification of genomic DNA. We recommend that you run a no-RT control reaction to confirm that there was genomic DNA contamination:
- Inactivate the RT enzume by incubation the Master Mix at 95 degrees C for 5 min.
- Allow the Master Mix to cool to room temperature.
Note: The PCR hot-start mechanism will reactivate.
We also recommend treating the RNA sample with DNAse I.
For Custom TaqMan Gene Expression Assays, you can also design an assay that spans an exon-exon boundary. See Custom TaqMan Assays Design and Ordering Guide (Pub. No. 4367671).
When automatic baseline is used, the software raises the threshold bar to avoid the elevated baseline. We recommend that you use a manual Ct, then manually adjust the threshold.
Most likely the baseline was set too high. We recommend that you rest the lower value of the baseline range or use an automatic baseline.
Most likely the RT-PCR Reaction Mix was not thoroughly combined. We recommend that you repeat the assay, and follow instruction for mixing the reagents. Please see the assay user guide for mixing instructions.