PCR, qPCR and qRT-PCR

Scientific creativity and repetitive tasks do not go well together.  There is nothing worse than having to repeat the same task over and over again – I know somebody who quit science because of this and became a castle curator. So how do you minimise the amount of one of the most repetitive tasks –…

In a recent article, I gave some tips about how to obtain good results with sequencing DNA after bisulfite conversion (it contains some tips that apply to the approach described in this article, too). Bisulfite sequencing is a very useful technique if you want to know the methylation status of every CpG in your genomic…

Comparing and measuring gene expression is certainly an integral part of research—gene expression patterns continue to show us how different cell networks are regulated, and point to new biological pathways and possible treatments for disease. But one crucial part of gene expression lies in making sure that differences in gene expression are due to gene…

During my postgraduate studies, I did literally one PCR reaction with a pre-optimised protocol on a not especially difficult template. So my karma came back with vengeance, when as a part of my first postdoc I had to amplify a template containing a 35 bp-long GC-rich stem-loop, which proved to be extremely difficult. This was…

For applications such as site-directed mutagenesis, it is often recommended that you use a proofreading polymerase (also known as high-fidelity polymerases) to minimize the risk of introducing unintended point mutations.  But what is a proofreading polymerase?  What makes them different from other polymerases?  And when should you use them?  Read on to learn more… What…

Using UNG is a great trick for PCR amplicon decontamination, but is it any good for rtPCR?

Primer design can sometimes feel like more of an art than a science, and designing the best primer can significantly affect the success or failure of your experiments. Here are a few tips on optimizing primer design for several different applications: PCR amplification/cloning One of the most common primer-based applications is cloning.  The desired amplicon…

Northern and Southern blotting are now a thing of the past. They’ve been replaced with a faster and more quantitative technique. No longer do we wait days to know whether a gene is expressed. We can have the answer in 45 minutes! Real-time PCR is now commonly employed in almost all molecular biology laboratories to…

One of the very first things you need to do when getting set up for quantitative PCR (qPCR) is to determine the efficiency of the assay because knowing the assay efficiency is critical to accurate data interpretation. Here’s how.

PCR is highly sensitive, but the downside of that very property is that it makes the technique prone to producing false-positives. In labs where PCR is a staple, like the one I work in, any false-positives are more often than not due to amplicon contamination. A broken capillary or a PCR plate left carelessly at…

One of the great features of PCR is its excellent sensitivity as we know. And many articles describe real-time qPCR as an added leap forward in that sensitivity – to the point where it has become a standard feature of a new assay description Indeed, I’m currently developing a new qPCR assay to replace a…

If you’re like many researchers, problems with PCR amplifying high GC DNA templates will be a major annoyance for you.  Many strategies developed to overcome this issue. Betaine is the most common PCR additive used to enhance amplification of GC rich sequences because of its ability to dissolve secondary structure that blocks polymerase action.  But…

qPCR is a technique used daily in most labs, but the first step, designing your qPCR primers, can be the biggest obstacle to even getting started. Without a good pair of primers, you can’t start asking the real questions and generating data.  And sometimes the effort involved in optimizing an assay for high efficiency and sensitivity…

Hydrolysis probes, commonly also referred to as TaqmanTM is a very popular chemistry for real-time PCR. In this article I will compare hydrolysis probes with PlexorTM. But first, a quick overview of hydrolysis probes. Hydrolysis probes, an overview Hydrolysis probes are a popular detection chemistry for monitoring sequence-specific amplification in RTPCR. Just like with  SYBR…

Nobel Laureate Kary Mullis is generally credited with inventing the polymerase chain reaction, but his discovery owes a lot to a microbiologist who loved to travel, some refuted assumptions of what can live in hot springs, and a now-closed field station in Yellowstone National Park. Here’s the story. In the 1960s, Thomas Brock was a…

qRT-PCR (quantitative reverse transcription-polymerase chain reaction) is now the gold standard technique for mRNA detection and quantification, sensitive enough to enable quantification of RNA from a single cell. The reverse transcription (RT) step is the main source of variability in a qRT-PCR experiment, so an optimal reverse transcription is essential for a reliable and successful…