STRanalyses

STR analyses refer to the examination of short tandem repeat regions in DNA, where 2- to 6-base pair motifs are repeated in tandem. The number of repeats at many STR loci varies among individuals, making STR profiles highly discriminatory. STR analysis is a standard method in forensic genetics, paternity testing, and population genetics.

Most STR analyses use multiplex PCR to amplify a panel of STR loci in a single reaction. The resulting fragments are separated by capillary electrophoresis and sized to infer the number of repeats at each locus. An individual's genotype is typically reported as one or two alleles per locus, and data are combined across loci to form a profile.

In forensics, STR profiles are compared with reference samples originating from crime scenes, victims, or suspects. The strength of a match is expressed statistically, for example as a random match probability or likelihood ratio. Internationally, standardized kits and panels (such as CODIS core loci) are used with databases to support identification and investigative leads. Panels may differ by country or kit, but generally emphasize short amplicons for compatibility with degraded DNA and high discrimination power.

Data quality controls, internal size standards, and proficiency testing underpin reliability. Special considerations apply to mixtures, partial profiles, or low-template DNA, which can yield stutter peaks, allele dropout, or imbalanced peaks. Limitations and ethical considerations accompany STR analyses. Physical degradation, laboratory contamination, or statistical interpretation can affect conclusions. Descriptive reporting and adherence to international guidelines aim to ensure accuracy, transparency, and privacy protection in forensic and research contexts.