Final answer:
The Polymerase Chain Reaction (PCR) is a method used to amplify specific regions of DNA, significantly enhancing specificity and yield. It differs from DNA cloning which involves digesting and religating DNA into a vector. PCR is a versatile tool in DNA research, medical diagnostics, and criminal forensics.
Step-by-step explanation:
The process of PCR amplification is a revolutionary method developed by Kary B. Mullis for amplifying a specific DNA segment. Unlike methods that involve digesting DNA with restriction enzymes and then religating it to form a recombinant DNA molecule, PCR directly focuses on multiplying the DNA segment of interest. By rapidly heating and cooling the sample, PCR is able to denature DNA strands, anneal specific primers to the target sequence, and extend the annealed primers by a DNA polymerase, typically Taq polymerase. During the second cycle of PCR, the amplified DNA becomes more abundant than the original template, making it more likely for the primers to anneal to the amplified DNA and synthesize the desired product, thus enhancing the specificity and yield of the target sequence.
Amplifying by PCR rather than digesting ensures that the amplified DNA cannot religate without the insertions of additional sequences, as it would occur in cloning processes. This feature of PCR is particularly advantageous when the goal is to obtain pure samples of a specific DNA sequence without cloning it into a vector for propagation in bacteria. However, if the intent is cloning and recombination, PCR alone won’t suffice; you need to follow the process with additional steps for inserting the amplified DNA into a cloning vector, digesting with restriction enzymes, and ligation.
The prime distinction between PCR and cloning is how each method is used in the lab. PCR is utilized extensively in DNA research for applications such as gene analysis, medical diagnostics, and criminal forensics. As PCR can amplify DNA from minute quantities — even a single cell’s worth or degraded fragments from fossils — it has become an indispensable tool for researchers and scientists across multiple disciplines.