chemistry

Quantitative PCR instrument

Quantitative PCR instrument is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Quantitative PCR instrument rather than just read about it. In short: A quantitative PCR instrument, also called real-time PCR machine, is an analytical instrument that amplifies and detects DNA. It combines the functions of a thermal cycler and a fluorimeter, enabling the process of quantitative PCR.

Key takeaways

Quantitative PCR instrument belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Quantitative PCR instrument to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Quantitative PCR instrument from memory before moving on to harder problems.

Reference excerpt

A quantitative PCR instrument, also called real-time PCR machine, is an analytical instrument that amplifies and detects DNA. It combines the functions of a thermal cycler and a fluorimeter, enabling the process of quantitative PCR. Quantitative PCR instruments detect fluorescent signals produced during DNA amplification, which correlate with the amount of DNA generated. This allows for precise quantification of specific DNA present in a sample. These instruments are used in many applications, including gene expression analysis, detection of genetic variations, genotyping, and diagnostics of bacterial and viral pathogens. The first quantitative PCR machine was described in 1993, and two commercial models became available in 1996. By 2009, eighteen different models were offered by seven different manufacturers. Prices range from about 4,500 to 150,000 USD. Many configurations of real-time PCR instruments became available on the market, with most commonly used systems designed to accommodate 96- or 384-well plates. Principal performance dimensions include thermal control, fluorescence detection (fluorimetry), and sample throughput. A quantitative PCR instrument is usually equipped with integrated software for real-time data acquisition and analysis, including quantification, melting curve analysis, and quality control metrics. Most systems use Peltier-based thermal blocks.

Thermal control Efficient performance of quantitative PCR requires rapid, precise, thermal control. 30 cycles of PCR have been demonstrated in less than 10 minutes. Rapid cycling provides several benefits, including, reduced time to result, increased system throughput and improved reaction specificity. In practice however, engineering trade-offs between ease of use, temperature uniformity, and speed, mean that reaction times are typically more than 25 minutes. Thermal non-uniformity during temperature cycling contributes to variability in PCR and, unfortunately, some thermocyclers do not meet the specifications claimed by manufacturers. Increasing the speed of thermal cycling generally reduces thermal uniformity, and can reduce the precision of quantitative PCR. The temperature uniformity also has a direct effect on the ability to discriminate different PCR products by performing melting point analysis. In addition to uniformity, the resolution with which instruments are able to control temperature is a factor which affects their performance when performing high resolution melting analyses. Therefore, speed, precision and uniformity of thermal control are important performance characteristics of quantitative PCR instruments.

Fluorimetry Quantitative PCR instruments monitor the progress of PCR, and the nature of amplified products, by measuring fluorescence. The range of different fluorescent labels that can be monitored, the precision with which they can be measured, and the ability to discriminate signals from different labels, are relevant performance characteristics. By using an instrument with sufficient optical channels and extensive assay optimisation, up to 7 separate targets can be simultaneously quantified in a single PCR reaction. However, even with extensive optimisation, the effective dynamic range of such multiplex assays is often reduced due to interference between the constituent reactions. The noise in fluorescence measurements affects the precision of qPCR. It is typically a function of excitation source intensity variation, detector noise and mechanical noise. Multi factorial analysis has suggested that the contribution of mechanical noise is the most important factor, and that systems with no moving parts in their optical paths are likely to provide improved quantitative precision. In addition, when performing high resolution melting analyses, one factor that affects the sensitivity of heteroduplex detection is fluorimetric precision. Therefore, the number of optical channels and the level of noise in fluorescence measurements are also important performance characteristics of quantitative PCR instruments.

Illustrations

Worked examples

Example 1 — a first encounter with Quantitative PCR instrument

Start with the simplest possible case. Write down what Quantitative PCR instrument claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Quantitative PCR instrument before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Quantitative PCR instrument ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Quantitative PCR instrument

In research: Quantitative PCR instrument appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Quantitative PCR instrument in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Quantitative PCR instrument is common in secondary-school and first-year university syllabi. It links to neighbouring topics Molecular biology laboratory equipment, Polymerase chain reaction, so understanding it makes those chapters shorter.
In everyday life: Look for Quantitative PCR instrument outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Quantitative PCR instrument in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Quantitative PCR instrument means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Quantitative PCR instrument out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Quantitative PCR instrument in simple terms?

Why does Quantitative PCR instrument matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Quantitative PCR instrument?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Quantitative PCR instrument.