Abstract
The interpretation of mixed DNA profiles is often undertaken by determining to what
extent possible genotype combinations may be eliminated from consideration. This requires
an understanding of the variability in height or area for the two alleles of a heterozygote
(heterozygote balance), and in the variability of mixture proportion or mixture ratio
across loci.
We present here empirical data to help assess the magnitude of this variability for
Identifiler™ profiles.
We find that heterozygote balance is affected by peak height as expected and that
at heights above 267RFU the two peaks of a heterozygote demonstrates a peak height
ratio between 0.6 and 1.66.
For mixtures we introduce a concept, APH, the average peak heights of the active alleles. Above an APH of 110RFU mixture proportion demonstrated variation no more than 0.2 from the average
across loci.
Mixture ratio variability was affected by both the mixture ratio, Mr per se and by the APH. The function (2APH/(1 + Mr)) appears to be a reasonable predictor of the variability and approximates the expected
peak height of the minor alleles. At (2APH/(1 + Mr)) ≥ 300RFU the mixture ratio at a locus is expected to be within a factor of 2 of the
average across loci.
Keywords
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References
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- DNA commission of the International Society of Forensic Genetics: recommendations on the interpretation of mixtures.Forensic Science International. 2006; 160: 90-101
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Article info
Publication history
Published online: August 05, 2009
Accepted:
July 9,
2009
Received in revised form:
June 2,
2009
Received:
February 17,
2009
Identification
Copyright
© 2009 Elsevier Ireland Ltd. Published by Elsevier Inc. All rights reserved.
