INTERPOL HANDBOOK ON DNA DATA EXCHANGE AND PRACTICE

Detail of Step 4-Figure 1 - Separation and visualization of the DNA profileRoutine forensic DNA profiling targets markers on the DNA known as short tandemrepeats (or STRs). STRs first emerged as potential forensic markers in the early 1990sand quickly demonstrated important advantages as a forensic technique. In particular,their small molecular size meant the tests were more sensitive, requiring as little as0.2–0.5ng of DNA. This is 100 to 250 times more sensitive than the original DNAprofiling techniques. This also meant that these loci had improved reliability when theDNA was highly degraded.Analysis of STRs has advanced to the point where up to 16 individual STR markersare combined into a single test. This technique (known as multiplexing) increases thediscriminating power of the DNA analysis without compromising the overall sensitivityof the test, or its suitability in the forensic context.year of release name no. of loci1997 AmpFlSTR Profiler Plus® 101998 AmpFlSTR COfiler® 71999 AmpFlSTR SGM Plus® 112001 AmpFlSTR Identifiler® 162001 PowerPlex® 16 16Table 3: STR multiplexes commonly used in forensic DNA profilingNote that we have three types of DNA analysis:1. Set of markers used for national DNA database that can provide identification of anindividual through direct comparison2. Markers such as Y-STRs and mtDNA that can exclude numerous people but may notbe sufficient for identification/individualisation in its own right3. Other markers that may assist investigators by providing an indication of aspectssuch as geographical origin, physical characteristics etc.IN THE LABORATORY PAGE 31