Polymerase chain reaction (PCR) is a laboratory technique used to amplify small amounts of DNA. It’s used in many fields, including genetics, medicine, and forensics. In this article, we’ll break down the basics of PCR, explain how it works, and look at some of its applications in real-world situations.
What Is Polymerase?
You may be surprised to learn that the polymerase enzyme is an enzyme that makes DNA. It performs this vital function by copying single strands of nucleotides, DNA building blocks, and assembling them into double-stranded DNA. This was observed in a study published on the NCBI website.
Because of its ability to make copies, this enzyme has become an essential tool in molecular biology research and is used in several different applications, including PCR.
What Is Polymerase Chain Reaction?
Polymerase chain reaction (PCR) was discovered by an American biochemist, Kary B. Mullis, in 1983. He received a Nobel Prize in 1993 for the invention. PCR can amplify specific genes from tiny amounts of DNA or RNA by making multiple copies of the target sequence over a short period. The number of copies it can produce depends on which type is used.
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Some versions are more efficient than others when amplifying small fragments but have lower fidelity, producing more errors and false positives during analysis. For example, one type called TAQ Polymerase produces many more false positives than another commonly used variant known as KOD.
PCR uses a DNA polymerase enzyme to make many copies of a specific region of a DNA strand. The process can be repeated to generate thousands or even millions of copies. This makes it possible for PCR to detect very small amounts of DNA in a sample and amplify any type of genome sequence.
PCR is an invaluable tool in the laboratory that allows scientists and doctors to identify genetic disorders like Huntington’s disease, autism spectrum disorder, and cancerous tumors at earlier stages than other methods would allow them to do so.
Hence, the use and demand for PCR are increasing. According to a market analysis done by Fortune Business Insights, the PCR market was valued at $7.1 billion in 2020 and is expected to reach $13.75 billion in 2028, growing at a CAGR of 8.4%
TAQ Polymerase and PCR Primers
PCR uses the enzyme TAQ polymerase to make many copies of a specific DNA segment. This enzyme helps the reaction proceed by adding nucleotides to the 3′ end of each primer. The newly synthesized DNA is then copied into two daughter strands identical to the original strand and can be used as templates in another round of replication.
The TAQ DNA polymerase can be helpful in many applications, from forensics to diagnosis. Amino acids can help signify the speed of TAQ DNA polymerase processes. A study published in the Frontiers Journal found that a single amino acid change to TAQ DNA polymerase can enable faster PCR and strand displacement.
The primers are short DNA sequences that bind specifically to a specific region on one strand of an amplicon (the product). Using a unique pair of primers allows you to target one area on your sample and amplify only that part. Primer pairs have been designed for every possible use, so chances are good that if you need something amplified, there’s already a primer available.
Applications of PCR
PCR is used across multiple disciplines and sectors of medicine and health. Here are some of the applications of PCR.
PCR Is Used to Amplify a Specific Region of a DNA Strand
You can use PCR to amplify a specific region of a DNA strand. This means that as you copy that section repeatedly, you’re making it bigger so that it’s easier for scientists to see what’s going on in the genome. The Genome.gov website defines gene amplification as increasing the number of genes in a genome.
The first step is to make copies of your sample, called primers. The primers are created by taking little bits of DNA from around where you want to start copying and putting them at the other end of your sample. Then, special enzymes create new copies based on these newly created primers. These new copies are made from scratch. They don’t come from anything else.
Once those new copies have been made, they get copied again with another set of primers until there are enough for scientists to use for research purposes. By doing this, scientists can see how much gene expression there is in different types of cells or even different organs.
PCR Can Help With the Diagnosis of Infectious Diseases
PCR is used to diagnose infectious diseases. For example, if you suspect someone has an Epstein-Barr virus infection, the doctor will typically order a PCR test to detect the presence of EBV DNA from saliva samples. If the results are positive, your patient is infected with this virus. Similarly, PCR can detect specific genes or DNA sequences in infectious diseases such as HIV and hepatitis B (HBV).
PCR-based diagnosis can be made with both target-specific and broad-range methods. The main advantage of using PCR in diagnostics is its ability to detect very small amounts of target DNA molecules in body fluids like blood or saliva. This makes it possible for medical professionals to identify viruses at extremely low levels without waiting for symptoms to appear.
PCR Can Help in Forensic Analysis
PCR can be used in the forensic analysis of crime scene samples. PCR is used to identify DNA from a single cell. Because it allows so much genetic information to be obtained from a small sample, it’s beneficial for cases with limited evidence.
For example, imagine you are investigating a murder, and the only thing left behind at the crime scene are cigarette butts belonging to your prime suspect. You could analyze these cigarette butts using PCR to determine whether this person smoked them. If they were not, your suspicion would be cleared, and you could move on with another lead.
The primary use of PCR in forensics is in amplifying short tandem repeat (STR). Moreover, the primers from PCR are also helpful in efficiently analyzing degraded and challenging samples.
PCR Can Help Detect Genetic Diseases
PCR can be used to detect genetic diseases, like cystic fibrosis, or genetic mutations that cause diseases like sickle cell anemia.
This test is also commonly used to detect genetic abnormalities such as Down syndrome and Klinefelter’s syndrome. Some people may opt for this testing if they have a family history of certain cancer or other rare disorders.
PCR is used in genetic analysis, forensics, and the diagnosis of infectious diseases. It has many applications in medicine, but it also has uses outside of this area. For example, PCR is used in paternity testing because it allows us to look at DNA from children and compare them with their parents’ genes, which is impossible using other methods such as blood samples or cheek swabs.