Short tandem repeat analysis
Short tandem repeat analysis (Forensic Science)
Since the 1990’s, the analysis of short tandem repeats (STRs; also called microsatellites) as a method of DNA (deoxyribonucleic acid) identification has gained prominence over the original restriction fragment length polymorphism (RFLP) protocol developed in 1985. The original method required that a relatively large amount of nondegraded DNA (about 100 nanograms) be isolated from a forensic sample and took several days to process. It measured the variation in the number of repeating units of DNA that were typically fifteen to fifty base pairs in length, also called minisatellites. This process is also referred to as the analysis of variable number of tandem repeats (VNTRs).
STR analysis has several advantages over the RFLP protocol: It requires about one hundred times less DNA, it can be completed within a few hours, and it exhibits less sensitivity to DNA degradation. The first two advantages come about mainly because of the coupling of this procedure with the polymerase chain reaction (PCR), also developed during the 1980’s. PCR allows for the rapid amplification of trace amounts of DNA using a set of DNA “primers” that bind to the sequence of interest and use it as a template to make millions of copies. The final advantage is the result of the decreased size of the DNA fragments that are analyzed, typically only a few hundred base pairs in length. It follows that, as the length of DNA being analyzed decreases, so does the...
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