QuantiTect PCR Kits

In one-step RT-PCR, both reverse transcription and amplification are performed in the same tube. Upon completion of reverse transcription, the reaction temperature is raised to reach denaturation/PCR enzyme activation temperature and the thermal cycling (PCR) begins. One-step RT-PCR generally uses gene-specific primers for both the RT and PCR steps. The procedure is fast, easy to automate, and minimizes the risk of contamination due to fewer handling steps.

In two-step RT-PCR, the RNA is first transcribed into cDNA using oligo-dT primers, random oligos, or gene-specific primers. An aliquot of the RT reaction is subsequently added to the real-time PCR reaction in a second tube. Choice of different types of RT primers allows the analysis of different transcripts by PCR from one RT reaction. Most commonly, an oligo-dT primer is used for the RT step, followed by PCR with a pair of gene-specific primers. Precious RNA samples can be immediately transcribed into more stable cDNA for later use and long-term storage.

The advantages of each method are summarized below:

Optimized one-step and two-step RT-PCR kits compatible with any real-time cycler are available from QIAGEN. For further details, please see our online section on 'Critical factors for successful gene expression assays', or download our Brochure 'Critical Factors for Successful Real-Time PCR'.

This depends on the amount of contaminating amplicon. If the contamination is high (e.g., 10e6 copies), then there will still be traces of amplicon remaining. However, we expect a reduction by a factor of around 1000 using QuantiTect +UNG Kits (i.e., after UNG pretreatment, only 0.1% of the initial contamination will still be present in the reaction).

The reduced reaction volume recommended for QuantiFast PCR Kits compared to QuantiTect PCR Kits allows more efficient temperature transfer during short cycling steps.

The presence of ROX as passive reference dye in the Master Mix of the QuantiTect Multiplex PCR Kit and the QuantiFast Mutliplex PCR Kit limits the use of these kits to triplex PCR on 4-channel real-time cyclers. This is because the ROX dye occupies the channel for detecting probes labeled with ROX, Texas Red, or other equivalent dyes.

However, 4-plex PCR is possible on on instruments equipped with at least 5 channels. Alternatively, if you have a 4-channel real-time cycler that does not use ROX passive reference dye (e.g., iCycler iQ, Rotor-Gene 3000, Mx4000, Mx3000P, Smart Cycler II, LightCycler 2.0), you can use the QuantiTect Multiplex PCR NoROX Kit or the QuantiFast Multiplex PCR +R Kit to perform 4-plex PCR.

Please see table “Real-Time, Multiplex PCR on a Wide Range of Real-Time Cyclers” for compabilities of the QuantiTect Multiplex kits with different real-time cyclers.

Replicates in real-time PCR may have different plateau heights due to differences in the reaction kinetics for each sample. Even though replicates start out with identical template amounts, the rate at which reagents are being depleted, and the point when exponential accumulation of PCR product stops and becomes linear, differ between replicates. This will result in different plateau heights, the stage where PCR reactions have come to a halt, and little or no additional PCR product is being amplified. You can find further information in Chapter 'Quantification of target amounts' of our Brochure "Critical Factors for Successful Real-Time PCR".

Fluorescent oligonucleotides should be stored in the dark, as light can slowly degrade the fluorescent moieties. For optimal long-term storage of fluorescent dye-labeled probes (except Cyanine 570, Cy3.5, Cyanine 670, and Cy5.5), the oligos should be resuspended in a slightly basic solution (e.g., TE buffer at pH 8.0). If resuspended below pH 7.0, the probe can degrade. We recommend to aliquot the sample, and store the aliquots at -20°C.

Note that Cyanine 570, Cy3.5, Cyanine 670, and Cy5.5 begin to degrade at a pH above pH 7.0. For best results, resuspend Cy-labeled oligos at pH 7.0, aliquot, lyophilize, and store at -20°C.

No. The master mixes in Rotor-Gene Kits contain dTTP instead of dUTP. If UNG treatment is required, we recommend using QuantiTect +UNG Kits. QuantiTect Kits are also compatible with the Rotor-Gene Q; however, the kits require a significantly longer cycling time.

Any DNA contamination will artificially inflate the SYBR Green signal, yielding skewed gene expression profiles and false-positive signals. The most common source of DNA contamination is from PCR products generated during previous experiments. Such contamination is most often due to the improper disposal of tubes, tips, and gels that previously came into contact with PCR products. Additionally, PCR products may also contaminate pipettors, racks, work pads, and commonly used reagents such as water and buffers. To minimize the risk of contaminating your experiment with extraneous DNA, the following steps should be taken:

• Remove a single aliquot of water from your PCR-grade stock, sufficient to complete the experiment. This minimizes the number of times that the stock container is opened, thereby minimizing contamination risks.
• Use only fresh PCR-grade reagents and disposable labware.
• Treat any labware (tubes, tips, and tip boxes) used in PCR with 10% bleach, before discarding.
• Maintain a dedicated workspace for PCR setup (perhaps a PCR-only hood), away from areas of the lab where post-PCR work is done, such as running gels, enzyme digestions, and cloning.
• Change the lab bench pads/papers often and decontaminate lab benches and labware (racks, pipettors, etc.) before each use by washing with 10% bleach, and/or exposing to UV light for at least 10 minutes. This serves to degrade and/or inactivate contaminating DNA.
• Before, during, and after the experiment, minimize the opening and closing of any tubes or plates used during the experiment.  

Recombinant DNA (recDNA) is very stable and represents the average size of mRNA. Due to the cloning and purification processes, obtaining recDNA can lengthen the overall process of generating standards.

Recombinant RNA (recRNA) and native RNA undergo reverse transcription as well as PCR, and mimic the natural process for mRNA in RT-PCR. Complicated cloning and purification of recRNA and instability of recRNA are two disadvantages for using recRNA as a standard. For further details please refer to the section "Generating Standard Curves" in Appendix D of the QuantiTect SYBR Green PCR Handbook.

QuantiTect Primer Assays are primer pairs designed and bioinformatically validated specifically for real-time RT-PCR with SYBR Green detection. To find a primer assay for your target gene of interest, please visit our GeneGlobe data base.

For best results, we strongly recommend using QuantiTect Primer Assays in combination with QIAGEN's products for SYBR Green-based Real-Time PCR and RT-PCR.

The primers of the QuantiTect Primer Assays are at a proprietary concentration that was specially optimized for sensitive and efficient amplification in any real time cycler. Always dilute these primers to a final work solution of 1x in your reaction, using either the QuantiTect SYBR Green PCR Kit or the QuantiTect SYBR Green RT-PCR Kit. Follow the instructions for use of the Primer Assays in the QuantiTect Primer Assay handbook.

The annealing temperature for QuantiTect Primer Assays should be 55^oC when used with the QuantiTect SYBR Green PCR Kit and the QuantiTect SYBR Green RT-PCR Kit.

Use of the QuantiFast SYBR Green PCR and QuantiFast SYBR Green RT-PCR Kits requires a combined annealing/extension step at 60^oC, as described in the QuantiTect Primer Assay Handbook.

Note that these Assays are guaranteed for use with the QuantiTect or QuantiFast chemistries only!

The storage time for QuantiFast PCR Kits is shorter than for QuantiTect PCR Kits, because all QuantiFast master mixes contain HotStarTaq Plus DNA Polymerase, instead of HotStarTaq DNA Polymerase which requires longer activation times.

Excessive exposure to elevated temperatures will result in reactivation of the HotStarTaq Plus DNA Polymerase, eventually leading to nonspecific amplification.

Yes, QuantiTect Primer Assays work very well under fast-cycling conditions. Results achieved with QuantiFast SYBR Green Kits are comparable to those achieved with QuantiTect SYBR Green Kits.

For each QuantiTect Primer Assay, we retrieve the sequence of the target gene from curated databases and exclude SNP regions from assay design.

We then use our proprietary algorithm to design assays that amplify RNA sequences only (i.e., at least one primer overlaps a splice site), provided that information on the position of splice sites is available. The assays are designed to provide optimal performance with QuantiFast and QuantiTect SYBR Green Kits.

After assay design, we validate randomly selected QuantiTect Primer Assays using real-time RT-PCR to check their compatibility with various real-time cyclers. Both two-step and one-step RT-PCR are carried out. Successful amplification of the target is indicated by the following factors: high sensitivity, high efficiency, high specificity (i.e., a single peak in melting curve analysis), and no primer–dimers in the no-template control (NTC).

To find a QuantiTect Primer Assay for your target gene of interest, please visit our GeneGlobe data base.

QuantiTect Primer Assays are optimized for an annealing temperature of 55ºC when using the QuantiTect SYBR Green PCR Kit (for two-step RT-PCR) or the QuantiTect SYBR Green RT-PCR Kit (for one-step RT-PCR) .

Increasing the annealing temperature will reduce PCR performance (sensitivity and PCR efficiency) when using QuantiTect Primer Assays with these kits.

Assuming 100% amplification efficiency, each step increase in Ct value represents a doubling in the amount of qPCR template. Therefore, evaluating the difference in Ct values between the qPCR assay, and its matching NRT control, leads to the following predictions:

Dissociation curves are carried out at the end of a PCR experiment by following a 3-step procedure.

First, all the components are denatured at 95°C, followed by complete annealing at a set temperature (based on the primer Tm values), followed by a gradual increase in temperature up to 95°C. Fluorescence intensity is monitored during this final temperature increase, resulting in the generation of a melting curve or dissociation curve.

By analyzing the first derivative of such a curve, you can readily assess the homogeneity of the PCR products, including the presence of primer–dimers, thereby determining the specificity of the PCR reaction. It is important to carry out such post-PCR analyses when using SYBR Green probe chemistry due to this reagent's lack of sequence specificity.

We highly recommend any QuantiTect or QuantiFast Kit for quantitative PCR on cDNA generated with the QuantiTect Whole Transcriptome Kit.

Depending on the qPCR instrument, time savings when switching from standard cycling (e.g., QuantiTect PCR Kits) to fast cycling using QuantiFast Kits range from 40% to 60%.

Even when detecting low-abundance targets, we recommend using no more than 500 ng/reaction of DNA (for PCR kits) or RNA (for RT-PCR kits). Generally, 1–100 ng template should be sufficient and for abundant transcripts as little as 1 pg can be used.

Template purity is important if large volumes of low concentration template are to be added to the reaction. Using DNA or RNA purified with QIAGEN products, the template can contribute up to 40% of the final reaction volume as long as the recommended template amounts are not exceeded. If cDNA from an RT reaction is used as template, the volume of undiluted RT reaction added should not exceed 10% of the final PCR volume.

No, QuantiTect Primer Assays are supplied as lyophilized, premixed primer pairs. Reaction components for SYBR Green real-time RT-PCR must be purchased separately.

• For two-step RT-PCR, the QuantiTect Reverse Transcription Kit and QuantiTect SYBR Green PCR Kit are recommended
• For one-step RT-PCR, the QuantiTect SYBR Green RT-PCR Kit is recommended

To find a QuantiTect Primer Assay for your target gene of interest, please visit our GeneGlobe data base.

Compatible reporter dye combinations for different real-time cyclers are listed in the "Important Notes" section under 'Suitable combinations of reporter dyes' in the QuantiTect Multiplex PCR Handbook and the QuantiTect Multiplex PCR NoROX Handbook. 

Shorter amplification products facilitate high PCR efficiencies. Ideally, amplicon length should be less than 150 bp for optimal amplification efficiency. PCR efficiencies close to 100% are a crucial prerequisite for accurate quantification of target copy numbers in real-time PCR.

For quantification of RNA, we strongly recommend using RNA molecules as standards. Use of in vitro transcripts as standards takes into account the variable efficiency of the RT reaction. An alternative to the use of in vitro transcripts as RNA standards is the use of a defined RNA preparation (e.g., from a cell line or virus preparation), for which the absolute concentration of the target has already been determined.

For quantification of DNA, several types of DNA can be used, such as plasmids, PCR products, or genomic DNA.

For more information, see Appendix E 'Generating Standard Curves' in the QuantiTect Probe PCR Handbook.

QuantiTect PCR +UNG Kits are available as 200-reaction kits only.

Rotor-Gene Kits are specifically developed for the Rotor-Gene Q PCR Cycler. The unique rotary system of the cycler combined with the kits’ proprietary buffer system enable ultrafast cycling. Rotor-Gene Kits do not contain ROX dye since no normalization to a passive reference is required. Also, Rotor-Gene Kits do not contain dUTP; therefore, UNG pretreatment is not possible.

Yes, probes and primers can be added to the QuantiTect Probe PCR- and the QuantiTect Probe RT-PCR Master Mix. This master mix can be stored at -20°C for up to 50 days, with a maximum of six freeze-thaw cycles (tested in our labs).

The master mix must be stored protected from light to avoid bleaching of the fluorescent probe. However, the QuantiTect RT Mix should be stored separately at –20°C, because the reverse transcriptases are sensitive to freezing in an aqueous environment. The QuantiTect RT Mix should be added to this master mix just prior to adding the template RNA and placing the reactions into the thermal cycler.

We have compared QuantiFast Kits and QuantiTect Kits using around 30 different assays (using both SYBR Green and Probe detection for each assay).

QuantiFast Kits gave identical or sometimes better Ct values than QuantiTect Kits (except for very long amplicons). Therefore, scientists switching from QuantiTect to QuantiFast Kits can, in most cases, obtain comparable results.

Yes - dTTP in the QuantiTect Master Mix in QuantiTect SYBR Green and Probe PCR Kits is partially substituted by dUTP, therefore allowing treatment with uracil-N-glycosylase.

However, only heat-labile UNG can be used for one-step RT-PCR with the QuantiTect Probe RT-PCR and SYBR Green RT-PCR Kits. This is because heat stable UNG (isolated from E. coli) will destroy any cDNA synthesized during the RT step at 50°C. Heat-labile UNG will have lost any activity after a few minutes of the RT-step and therefore cannot interfere with cDNA synthesis.

For heat-stable uracil-N-glycosylase, please use the QuantiTect SYBR Green PCR +UNG (cat. no. 204163) or QuantiTect Probe PCR +UNG Kits (cat. no. 204363). Both kits include heat-stabile uracil-N-glycosylase. Although QIAGEN UNG is inactivated by incubation at 95°C for 15 minutes, the enzyme may exhibit residual activity at lower temperatures due to refolding. Therefore, it is recommended to perform subsequent PCR using a temperature of 55°C or above for the annealing step.

• LightCycler: We do not recommend performing real-time, multiplex PCR using TaqMan® probes or QuantiTect Assays on the LightCycler system due to the limitations of its optical detection system.
• LightCycler 2.0: Information on using the QuantiTect Multiplex PCR NoROX Kit with the LightCycler 2.0 system is provided in the QuantiTect Multiplex PCR NoROX Handbook. You will find the recommendation for the LightCycler 2.0 system in the chapter 'Important Notes' under "Suitable combinations of reporter dyes".

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If the extra peaks seem irregular or noisy, do not occur in all samples, and occur at temperatures less than 70 ºC, then these peaks may not represent real PCR products and instead may represent artifacts caused by instrument settings.

Usually extra peaks caused by secondary products are smooth and regular, occur reproducibly in most samples, and occur at temperatures greater than 70 ºC. Characterization of the product by agarose gel electrophoresis is the best way to distinguish between these cases. If only one band appears by agarose gel then the extra peaks in the dissociation curve are instrument artifacts and not real products. If this is the case, refer to the thermal cycler user manual, and confirm that all instrument settings (smooth factor, etc.) are set to their optimal values.