TaqMan™ Gene Expression Master Mix, 1 x 5 mL - FAQs

What can I do to improve the sensitivity of my qPCR assay?

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)

How do I set the baseline for my qPCR experiment?

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).

How do I set the threshold for my qPCR experiment?

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).

I am not getting any amplification with my TaqMan Assay or SYBR Green primer set. What is causing this?

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.

I am getting amplification in my no-template control (NTC) wells in my qPCR experiment. What is causing this?

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.

My amplification curves have a funny shape in my qPCR experiment. What is causing this?

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.

What can I do if the amplification of my target gene is later than expected for my qPCR experiment?

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).

Can I use my SYBR Green primers for a TaqMan assay?

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.

Do I have to normalize my samples for comparative Ct experiments?

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).

What are the requirements for a relative quantification qPCR experiment?

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.

What are the requirements for a standard curve qPCR 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.

What is the difference between absolute quantification (AQ) and relative quantification (RQ)? How do I choose which method to use?

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.

Can I do a melt curve with a TaqMan assay?

No. A TaqMan probe, once cleaved, cannot be re-quenched. Therefore a melt curve does not apply when using a TaqMan assay.

What is the difference between TaqMan and SYBR Green methods of detection?

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.

How many replicates do I need to run for my qPCR experiment? What recommendations do you have for plate setup?

Please view this short video (https://www.youtube.com/watch?v=eIaPGhOjBQo), which explains some best practices for replicates and plate setup.

What are the different phases of a qPCR reaction?

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.

I'm trying to decide between purchasing a one-step or two-step RT-PCR kit. Can you review the advantages and disadvantages of each?

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.

Which other products has TaqMan Gene Expression Master Mix been tested with?

TaqMan Gene Expression Master Mix has been tested with TaqMan PreAmp Master Mix (Cat. Nos. 4391128, 4488593) and High Capacity cDNA Reverse Transcription Kit (Cat. Nos. 4368813, 4368814).

Is it possible to get an earlier Ct with the TaqMan Gene Expression Master Mix for my target?

Not necessarily. Performance comparisons should not focus on a direct comparison of Ct. Instead, the basis for comparison should be objective performance criteria, such as linear dynamic range and average PCR efficiencies calculated from the slope of a serial dilution of target.

What are the important features of the TaqMan Gene Expression Master Mix?

Here are the important features of the TaqMan Gene Expression Master Mix:

• High sensitivity
• Improved co-amplification of two targets (duplexing capability)
• Good specificity
• Robust, consistent amplification of difficult target sequences (GC and AT-rich targets)
• High quality

Does TaqMan Gene Expression Master Mix contain AmpErase UNG?

TaqMan Gene Expression Master Mix contains UDG (uracil-DNA-glycosylase). UDG refers to a superfamily of enzymes comprising six sub-families. Family I UDG enzymes are called UNG, after the uracil-N-glycosylase gene. The terms UDG and UNG are commonly used interchangeably because they perform the same function in qPCR, namely to remove Uracil from dU-containing DNA to prevent carryover contamination from previous PCRs.

Can I use TaqMan Gene Expression Master Mix to quantify PCR products with either the TaqMan or SYBR Green real-time PCR method on Bio-Rad real-time PCR instruments?

Yes, this is possible. However, note that all Applied Biosystems real-time PCR master mixes (including the TaqMan Gene Expression Master Mix) contain ROX dye as the passive reference dye. The software used with the Bio-Rad real-time PCR instruments does not calculate/normalize the signal between the reporter dye and ROX dye. Thus, when the TaqMan Gene Expression Master Mix is used on a Bio-Rad real-time PCR instrument, ROX dye will no longer work as a passive reference dye. Additionally, if you want to use Texas Red dye as a reporter dye on a Bio-Rad real-time PCR instrument, we do not recommend using an Applied Biosystems real-time PCR master mix because the emission wavelength of Texas Red dye is the same as that of ROX dye.

For SYBR Green applications, we have other validated master mixes, e.g., PowerUp SYBR Green Master Mix (Cat. No. A25741).

Can dU-containing DNA produced by amplification with dUTP be cut by restriction enzymes?

You will need to confirm with the manufacturer of the restriction enzyme you are using to find out whether or not it can recognize dUTP-containing DNA.

Find additional tips, troubleshooting help, and resources within our PCR and cDNA Synthesis Support Center.