PCR is a biotechnological invention that is used to analyze genetic material and synthesize copies of the same. It analyses the very tiny fragments of genetic material including the damaged material to a level which can be easily studied. For the past hundred years, PCR has been the most important scientific based technology; constituting the fastest method of obtaining DNA duplicates hence facilitating various researches on genetics. With just ten years down the line, PCR has changed life in many aspects since its invention. Since its invention by a scientist, Kary Mullis, it has been essentially used in many application in medicine and biological research applications. Such applications include cloning of DNA, during sequencing of genetic material, analyzing active genes especially in the diagnosis of diseases that are passed through generations. The basics of the technique are dependant of thermal cycling which involves several cycles involving heating and cooling of the genetic material being analyzed. The repeat of the two processes alongside polymerase enzymes is what results to melting of the genetic material and consequent replication of the same. It has been used widely from diagnosis of medical conditions to law courts to study of animal behavior among others. Its wide application has been related to its simplicity and the fact that it is less costly compared to other biotechnological techniques in addition to its speed when operating (Powledge, 2010).
Significance of PCR in molecular biology
The significant use of PCR on genetic material has been facilitated by the fact that all living things have their sequences of genetic material , DNA and RNA, made uniquely and specific to each species. For instance, in man, every single individual has his own unique sequence of DNA material. It is this uniqueness that makes it possible for scientists to trace the precise species from which a certain organism belongs to and relate organisms based on their genetic constitution. However, this process requires a remarkable amount of DNA for the study. On this aspect, PCR has been very helpful since it has the ability to manipulate the natural functioning of polymerase enzymes which are naturally present in all living things and function in copying genetic material, proofreading it and even correcting the miscopied material especially during transcription. So far, only PCR has the capacity to characterize and synthesize any specified piece of genetic material. It also has the capacity to pick up a specific material from a mixture and duplicate it. PCR does not require genetic material from a specific region but rather can use material from blood samples, hair, microorganisms as well as from plants and animals. In addition, PCR can analyze material as old as millions of years old (Rabinow 1998).
Basically, the entire process is very simple to all molecular biologists. It only requires a template, the material to be copied and two primers, short sequences of any genetic material. The primers are made up of four different bases under which different genetic materials are classified. The genetic material is made up of nucleotides which exist as chains. DNA exists as double strands of the nucleotides while RNA consists of only one strand just like the primers do. The sequences of the primers are known before the process since they are obtained from either side of the material to be copied (Janes 2002). This process is made more reliable by the easy availability of the primers which can be purchased from suppliers or made in the lab. PCR basically consists of three major steps. The process is initiated by separating the two strands from the helix creating individual units. This is followed by joining the primers to the templates of the original material. The final step involves the synthesis of new DNA where the polymerase enzymes moves along the template, reads it and matches it with complementary nucleotides resulting to formation of two helixes one of which is similar to the original template and the other consisting of new sequences. Automated machines for regulating temperature changes during this procedure have been developed to make the work much easier. Such machines are already available making the procedure much reliable and fast. In order for one to make as many copies as desired, all what needs to be done is to repeat the process using every newly synthesized strand. Since one cycle takes only around two minutes, million copies of the desired material can be made in less than hour, an operation which took a week or so before the invention of PCR (Mullis 1990).
The significance of PCR has been demonstrated in its many uses in many different aspects of life. One of the fields benefiting greatly from PCR is the medicine field where PCR is being used to detect and identify organisms that cause infectious diseases. Genetic related diseases, both inherited and those resulting from mutations are also being studied. PCR is enabling physicians to study very minute amounts of DNA from an infected cell by amplifying it to enable them identify the cause of infections. Medical analysis using PCR is proving to be more reliable than the previous methods due to the fast speed associated with the procedure especially where emergency health cases occur. PCR has been mostly used in medicine to study disease causing organisms that cannot be cultured (Powledge, 2010). For instance, PCR can detect the HIV virus soon after infection unlike other identification tests such as ELISA. Instead of looking for antibodies that the body of the infected person makes against the HIV virus like in the case of ELISA, PCR identifies the particular DNA specific to the HIV virus. PCR is the only molecular test that has been able to detect and identify the bacterial DNA that causes otitis media, a painful middle ear infection in children. Another infection, Lyme disease which is characterized by painful inflammation of the joints can be diagnosed early enough using PCR by detecting the causative organism’s DNA in the joint fluid. This way, early treatment can be done to prevent later complications of the disease other than the usual diagnosis which is based on appearance of symptoms which may lead to complication of the disease before it is even diagnosed. PCR can also detect several organisms transmitting sexual diseases with only a single swab. More so, unlike other molecular techniques, PCR has been used to differentiate strains belonging to the same genus. Basically, PCR is the most sensitive test for identification of infectious agents especially those that could not be identified by other methods due to their evasive behavior. PCR has also been used to detect variations in DNA resulting due to mutations most of which cause personality disorders (Powledge, 2010).
Use of PCR alongside scientific research can be used to yield predictive results concerning genetic constitution. For instance, sensitive study on mutations through PCR can reveal who is predisposed to the common personality disorders related to mutations. Some of these diseases may even be fatal therefore this knowledge may help affected people to initiate preventive measures. For instance, mutations in the tumor suppressor genes have been detected in the gastrointestinal tract. Through this test, people with high risks of developing colon cancer can be identified early enough. Similar tests have also been used to warn parents on getting babies due to the risky they could be faced with concerning genetically inherited diseases or disorders. PCR has also been widely used in parenting first by reassuring mothers that they can safety have children through confirmation of non existence of genetic diseases in both parents. Similarly, lives of infants can be saved by using PCR to determine whether the blood group of a mother is compatible to that of the fetus; if not treatment can be started in the womb to prevent disabilities and death cases caused by the incompatibility thanks to PCR invention.
PCR is principally the most important molecular technique in the field of biotechnology. Its major significance is the ability to produce as many copies of genetic material of any organism as possible (Don et al., 1991). It can therefore be used to study the cells that contain the genetic material in question. Even the very complex cells such as those of human beings have been analyzed especially concerning gene related diseases. Early diagnosis of various complex diseases that cannot be detected by any other diagnostic method has also been made possible by PCR. This way, many lives have and will continue to be saved by ensuring early treatment of such diseases. PCR has been commonly used in the genetic analysis in medicine and law where criminals can be traced through gene comparison which is similar to PCR application on diagnosis of diseases and other genetic concerns. What makes PCR even more reliable is the fact that the whole process is inexpensive, consumes less time and is very easy to carry out. With the increasing advancement in technology, PCR is expected to get much more reliable as researchers have already reported the possibility of analyzing and copying larger pieces of genetic material such as an entire genome of an organism. In addition, there are different types of PCR which allow specific application of the technique to further increase efficiency. However, just like many other technical applications, PCR is faced with some technical problems. One of the major problems that have been encountered in the running of the process is the contamination of the genetic material sample which in most cases results to production of much more than required amount of the genetic material. The major cause of this irregularity is the use of an already amplified genetic material may be from a previous experiment. This then results to introduction of contaminant molecules into the sample. This problem may be difficult to avoid especially medicine and law applications where human life is involved. Despite this problem, it is still no doubt that PCR is the very most significant invention in molecular biology up to date.
Don, R, et al., 1991. “PCR to circum spurious priming during gene amplification”. Nucl. Acids Res. 19, 4008
Janes, H. And Chen, B. 2002. “PCR Cloning Protocols”. Humana press, New Jersey. 2nd Ed
Mullis, K. 1990. “The unusual origin of the polymerase chain reaction”. Scientific American.
Powledge, T. 2010. “The polymerase chain reaction”. Web.
Rabinow, P. 1998. “What is PCR?” Web.