Single Source Profiles

STR loci provide the comparison units in a single-source analysis. At each selected locus, amplification produces DNA fragments whose sizes correspond to an individual’s alleles. Recording the allele pattern across the analyzed loci allows an evidence profile to be compared systematically with a reference profile for human identification.

PCR and capillary electrophoresis perform different but connected tasks. PCR amplifies the selected STR regions and produces fluorescently labeled DNA fragments, while capillary electrophoresis separates those fragments for detection. This sequence converts genetic material in the evidence into a measurable fragment pattern that analysts can evaluate and compare with references.

Single-source evidence provides one contributor’s allele pattern rather than a combination of patterns from multiple contributors. Analysts can therefore use the resulting profile as a clear comparison point when assessing a reference sample. This focused interpretation also makes single-source work a foundation for understanding the more complex problem of DNA mixtures.

An analysis proceeds from biological evidence to DNA extraction, amplification of selected STR loci, fluorescent fragment generation, and capillary electrophoresis. The resulting allele pattern is then compared with a reference sample. Keeping these stages distinct helps connect the original evidence to the profile used for identification, exclusion, relationship, or association assessments.

Reference-sample comparisons support several types of forensic conclusions, not just a possible identification. A profile may support an identity assessment, exclude an individual, investigate a biological relationship, or associate evidence with a person. The specific use depends on the comparison being made and the question posed by the investigation.

In biology, Single Source Profiles link molecular processes with human identification. DNA provides the genetic material, STR loci supply the analyzed regions, PCR amplifies them, and capillary electrophoresis resolves labeled fragments into an allele pattern. This chain shows how laboratory measurements of DNA can produce evidence for forensic comparisons and provide a basis for interpreting mixtures.