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STR Data Analysis and Interpretation for Forensic Analysts

Single Source Profiles

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Profiles developed successfully from a single contributor will display one or two alleles at each locus (excluding rare mutations). The profiles will have peak height percentages consistent with the laboratory's interpretation procedures, which were established through validation studies. All loci should be evaluated in interpreting profiles.

In general, a homozygous locus will show a single peak that is approximately twice the height of alleles seen at a heterozygous locus within the same dye color. This is due to the doubling of the signal from two alleles of the same size. If the peak height is not approximately twice that of alleles seen at a heterozygous locus, this may indicate a null allele or a primer-binding site mutation at this locus.

The peak height percentages may vary from locus to locus and should be assessed based on the laboratory's interpretation procedures. Low peak height percentages may indicate a mixed DNA sample or mutation at a specific locus.

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