Polymerase chain reaction (PCR)

The process of DNA profiling starts with the sample of an individual DNA, also known as the reference sample. In this case, the reference sample is the hair strand from the crime scene. The reference sample is analyzed, creating a DNA profile compared against another DNA sample in determining the match in the genes (Syngal et al., 2015).
The initial stage involves the extraction of the DNA from the cells and purified. The removal comes by breaking up the cell and the nuclear membranes to set DNA free in a solution. The DNA is then separated from all the other cellular components. After the extraction, the DNA can be analyzed.
The process of analysis in this technique mimics the DNA replication process but restricts it to a specific DNA sequence of interest. The DNA sample is denatured into separate individual polynucleotide strands by heating. The two oligonucleotide DNA primers then hybridize the DNA into two corresponding opposite DNAs stands sites such that the standard enzymatic extension of the active terminal of each primer moves toward the other primer. Replication Enzymes such as thermostable Tag polymerase which are tolerant to high temperatures are used, generating two copies of interest sequence (Kane, Shah, & Alfaro, 2019). The repeat of denaturation, hybridization, and extension leads to the growing number of copies of DNA of interest. The result in the PCR reaction is visualized using gel electrophoresis. The technique pulls DNA fragments through the gel matrix by electric current separating the fragments according to size.
In the forensic analysis, a specific genetic marker is examined to determine the suspect. The marker always comes in two alleles, one containing a single repeat while the other contains two copies of repeat. In the PCR reaction using primers flanking the repeat region, the first allele produces 20 bp DNA fragment while the second allele produces 30BP DNA fragment (Kane, Shah, & Alfaro, 2019).

Reference
Kane, S. R., Shah, S. R., & Alfaro, T. M. (2019). Development of a rapid viability polymerase chain reaction method for detection of Yersinia pestis. Journal of microbiological methods, 162, 21-27.
Syngal, S., Brand, R. E., Church, J. M., Giardiello, F. M., Hampel, H. L., & Burt, R. W. (2015). ACG clinical guideline: genetic testing and management of hereditary gastrointestinal cancer syndromes. The American journal of gastroenterology, 110(2), 223.