Many people are now familiar with the term “PCR” or PCR test results, as a PCR test is the most common way to detect the presence of COVID-19. However, most people make a choice between PCR or an antigen test, and that’s the extent of their knowledge. Polymerase chain reaction, also known as PCR, is a widely-used laboratory technique that replicates copies of one specific segment of DNA or RNA, allowing researchers to produce more DNA for studies, or to measure the point at which a signal is detected, allowing an analytical measurement of the starting amount of that DNA segment based on the number of cycles to reach the end detection point.PCR is used for many applications, including infectious diseases, genetic marking, molecular biology research, and ecology applications. Read on to learn more about PCR testing and PCR test results, liquid handling robots for PCR, and other automated systems that streamline PCR techniques in the laboratory.
What Is the PCR Process?
Quite simply, the goal of PCR is to copy segments of DNA or RNA. DNA replication in an organism is similar to how DNA is replicated in a laboratory, so a DNA polymerase enzyme is needed. The polymerase used for PCR and PCR lab test results is Taq, or Thermus aquaticus, which is utilized because it is extremely heat stable at 70°C, unlike other polymerases. A high level of heat is needed to separate (denature) the strands of DNA.
To create “new” DNA, the polymerase requires a primer. Primers are ~20 nucleotides in length and are pieces of single-stranded DNA. Two primers are used, which bind to opposite strands of the original DNA and bind to the template via complementary base pairing. Once the primers are bound, they are then extended by the polymerase, ultimately resulting in replication. There are three basic “steps” to the PCR process, whether you’re trying to understand PCR test results or are using PCR for another purpose. These include:
- Denaturation. The reaction is heated strongly (96°C) to denature DNA strands (separate double stranded DNA into single strands).
- Annealing. The reaction is cooled so primers can bind to DNA (55–65°C).
- Extension. The reaction temperature is raised slightly (72°C), so Taq polymerase can synthesize new strands of DNA by extending the primers.
However, performing PCR techniques manually is laborious and time-consuming and may not yield accurate results. PCR pipetting robots and other automation tools are used to speed up the process.
PCR Test Results – Different PCR Machines
PCR and PCR test results were first used in the 1980s and have essentially revolutionized the field of life sciences. After the initial denaturation (steps listed above) are performed, researchers then need to repeat the steps until the desired copies of a DNA sequence are reached. A robotic PCR machine is needed to complete the process.
A conventional PCR machine is the most common automated PCR setup robot type. In a conventional machine, the polymerase enzyme works with a primer connected to a strand of DNA. Conventional devices are used in forensic research, medical and diagnostic research, and the amplification and quantification of DNA. While a conventional PCR machine may offer PCR test results, other machine types are also used.
Quantitative PCR (qPCR) is a different type of machine. This one machine performs both the amplification of a target DNA sequence and the quantification of the concentration of DNA. qPCR machines use fluorescence-detecting thermocyclers to perform this process. qPCR machines are used for cancer detection, GMO detection, microRNA analysis, genotyping, and quantifying pathogens.
There are other PCR machines, PCR test results, and processes as well:
- Nested – This type of PCR increases the specificity and sensitivity of the reaction. The first set of primer binds to the outside of target DNA, amplifying a larger fragment. A second set of primer binds specifically at the target site in successive PCR reactions. This is userful for phylogenetic studies and in the detection of different pathogens.
- Hot Start – This type reduces contamination by keeping the elements of the reaction separate. Hot start keeps different elements of the reaction separate until the mixture hits the denaturation temperature after heating. Hot start reduces contamination risk and requires less effort than conventional PCR.
- Digital (dPCR) – Digital PCR machines are the most accurate and can either be droplet digital PCR (ddPCR), which uses emulsification and fluorescence, and qdPCR, which is based on integrated fluidic circuits. dPCR provides absolute counts of target DNA with increased sensitivity, precision, and reproducibility. qdPCR especially provides the most precise sample partitioning and lower variance than others.
It fully depends upon your applications as to which PCR machine may be best for PCR test results for you. You may also want to consider that liquid handlers help fully automate the PCR procedure when paired with a thermocycler and an automated reagent dispensing system.
Unsure of which PCR machine is best for your needs? If you need help designing the best workflow for your budget and space, contact Hudson Robotics for a detailed quote.
