Mixtures with Major/Minor Contributors

Mixtures with Major/Minor Contributors

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The presence of major and minor contributor(s) is distinguishable when samples display alleles that have distinct contrast in signal intensities. All loci should be used for this evaluation and laboratories should follow established procedures that are based upon validation studies.

Click here to view an animation about major and minor contributors to a sample.

The calculations of peak height/area percentages and percent contribution of donors can be used to support the declaration or a major and/or minor contributor.

In these instances, the DNA profile of the major source may be easily determined at unambiguous loci.

In general, determining the DNA profile of the major contributor is easier than determining that of the minor source.

Above is an electropherogram demonstrating a mixture.
The set of peaks on the right (FGA locus) represent a clear major and minor contributor: there are two tall peaks and two short peaks.
The set of peaks on the left (vWA locus) represent an ambiguous minor contributor. The major contributor appears to be a 17, 18. It is unclear, however, whether the major contributor is or is not masking the minor contributor, who could be a 16, 16; a 16, 17; or a 16, 18.

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