The polymerase chain reaction (PCR) is an enzymatic process by which a section of DNA can be duplicated as many times as desired. It is also referred to as polymerase chain reaction, which is why the method is also abbreviated to PCR. Today, this technique has become a very promising part of molecular biology, since, among other things, it can be used:
- To create the genetic fingerprint in the shortest possible time.
- When researchers do not have enough DNA.
- Detection of viral agents.
- Detection of genetic diseases.
- Studies of extinct species when only a small sample is available.
- Collect information at crime scenes.
For example, a mother can take a paternity test with a used fork, because, although there may not be enough DNA for the paternity test, the small amount of DNA collected can be multiplied using PCR. This laboratory method was invented in the 1980s by DNA chemist K. Mullis, and since then, his invention has gained great importance and has become an indispensable part of biological research. In 1993, the scientist received the Nobel Prize in Chemistry for this.
How does the thermal cycler multiply DNA strands?
With the help of a device, the thermal cycler, scientists can carry out PCR, hence its usefulness in molecular biology laboratories. The most important task of the device is to set the required temperature for the individual phases of the polymerase chain reaction. These occur during each PCR cycle:
- Denaturation.
- Hybridization.
- Elongation.
In general, DNA is present in its double helix structure at the beginning of the PCR method. However, in order for the DNA to double, it must change its structure and separate into two individual strands. Otherwise, no primers could accumulate in the course of the PCR and the polymerase would not be able to function either. Therefore, the thermal cycler, in a programmed manner, produces temperature changes at preset times for each of the phases to be carried out.
How does each of the phases of PCR occur?
To denature DNA, the hydrogen bonds by which the individual strands are connected are first cleaved. After all, there should ultimately be two individual DNA strands to which the complementary nucleotides can subsequently be attached. This means that the thermal cycler heats the DNA.
This happens for about half a minute, during which time the DNA inside the thermal cycler reaches temperatures of 95 degrees Celsius. As a result, the hydrogen bonds are broken. The result of denaturation is two individual DNA strands with which further work can be carried out.
In the next stage, hybridization, the two primers are applied to the individual DNA strands at approximately 60 degrees Celsius. The primers are short sections of DNA that bind to the individual strands. They serve as a starting point for the Taq polymerase and flank the target sequence of the DNA to be duplicated. It is important in this case that the primers are only complementary to the respective bases of the DNA section.
In the last stage, elongation, the heat-resistant Taq polymerase enzyme binds to the primers. From there, it synthesizes strands complementary to the individual DNA strands. In this case, the DNA polymerase migrates in the 5-3 direction and resorts to the bases in solution. These are bound to the starting DNA strand. Thus, in total, the complementary bases are connected to each other and the initial double strand is reproduced.
What are the areas of application of PCR?
PCR plays an important role in current research. With the help of PCR, time-consuming methods for detecting infection-causing agents, such as growing bacterial cultures from specimens, can be avoided. For example, this helps with coronavirus testing, where an infection must be detected as quickly as possible. Another example would be the detection of HIV infection.
It is also possible to detect inherited diseases with the help of PCR. First, mutations can be detected by studying the human genome. This is used, among other things, in prenatal diagnosis. Using PCR, genetic diseases can be detected in embryonic cells.
Researchers have already succeeded in reproducing fossils by PCR, even though the species had become extinct long ago. For this purpose, they used genetic material of an insect species from amber fossils and duplicated it. In police investigations, PCR is useful if only a small part of the DNA can be found at the crime scene. This section can be copied as often as desired with PCR and then used for a genetic fingerprint. Similarly, the polymerase chain reaction can also allow paternity testing.
Why choose the Kalstein thermal cycler for a molecular biology laboratory?
Kalstein allow you to exploit the full potential of PCR. These instruments allow precise temperature control, low noise operation and low power consumption. To review other technical data of this equipment, please click HERE and HERE, where you can also find prices, purchase details and quotations.