Interpreting simple STR mixtures using allele peak areas

Gill, Peter; Sparkes, Rebecca; Pinchin, R.; Clayton, Tim; Whitaker, Jonathan; Buckleton, John

doi:10.1016/s0379-0738(97)00174-6

Cited by 129 publications

(77 citation statements)

References 7 publications

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“…Accordingly, it was demonstrated that under the optimal 34 cycles regime, there was increased heterozygote imbalance. The incidence of stutter decreased with smaller DNA quantities but their peak areas were correspondingly greater than described by Gill et al [14] and this means that the guidelines described cannot be used. In addition, with increased PCR cycle number there was increased incidence of laboratory-based contamination that was unavoidable.…”

Section: Discussionmentioning

confidence: 70%

An investigation of the rigor of interpretation rules for STRs derived from less than 100 pg of DNA

Gill

Whitaker

Flaxman

et al. 2000

Forensic Science International

526

357

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By increasing the PCR amplification regime to 34 cycles, we have demonstrated that it is possible routinely to analyse ,100 pg DNA. The success rate was not improved (without impairing quality) by increasing cycle number further. Compared to amplification of 1 ng DNA at 28 cycles, it was shown that increased imbalance of heterozygotes occurred, along with an increase in the size (peak area) of stutters. The analysis of mixtures by peak area measurement becomes increasingly difficult as the sample size is reduced. Laboratory-based contamination cannot be completely avoided, even when analysis is carried out under stringent conditions of cleanliness. A set of guidelines that utilises duplication of results to interpret profiles originating from picogram levels of DNA is introduced. We demonstrate that the duplication guideline is robust by applying a statistical theory that models three key parameters -namely the incidence of allele drop-out, laboratory contamination and stutter. The advantage of the model is that the critical levels for each parameter can be calculated. This information may be used (for example) to determine levels of contamination that can be tolerated within the strategy employed. In addition we demonstrate that interpreting one banded loci, where allele dropout could have occurred, using LR 5 1/2f was conservative provided a that the band was low in peak area. Furthermore, we demonstrate that an apparent mis-match between crime-stain and a suspect DNA profile does not necessarily result in an exclusion. The method used is complex, yet can be converted into an expert system. We envisage this to be the next step.

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Section: Discussionmentioning

confidence: 70%

An investigation of the rigor of interpretation rules for STRs derived from less than 100 pg of DNA

Gill

Whitaker

Flaxman

et al. 2000

Forensic Science International

526

357

View full text Add to dashboard Cite

show abstract

“…The novel Y-STRs have more than doubled the number of known pentanucleotide markers and they include the first hexanucleotide repeat on the NRY (DYS448). These longer repeat motif STRs may be useful for improving the interpretation of sample mixtures [31,32]. Depending on the particular STR, the stutter peak heights of dinucleotide and trinucleotide repeats can be higher than 30% of their corresponding STR allele, while stutter products of tetranucleotides are approximately 15%, and pentanucleotide repeats may have stutter products of less than 1-2% [19].…”

Section: Discussionmentioning

confidence: 99%

Forensic value of 14 novel STRs on the human Y chromosome

Redd

Agellon

Kearney

et al. 2002

Forensic Science International

146

106

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We identified and characterized 14 novel short-tandem-repeats (STRs) on the Y chromosome and typed them in two samples, a globally diverse panel of 73 cell lines, and 148 individuals from a European-American population. These Y-STRs include eight tetranucleotide repeats (DYS449, DYS453, DYS454, DYS455, DYS456, DYS458, DYS459, and DYS464), five pentanucleotide repeats (DYS446, DYS447, DYS450, DYS452, and DYS463), and one hexanucleotide repeat (DYS448). Sequence data were obtained to designate a repeat number nomenclature. The gene diversities of an additional 22 Y-STRs, including the most commonly used in forensic databases, were directly compared in the cell line DNAs. Six of the 10 most polymorphic markers include the newly identified Y-STRs. Furthermore, these novel Y-STRs greatly improved the resolution of paternal lineages, above the level obtained with commonly used Y-STRs, in the European-American population. #

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“…Following Gill et al (1998) and Walsh et al (1996), stutter bands are understood to be allelic in origin and arise from slippage of the Taq polymerase enzyme. Only a single stutter band is typically observed and is four bases shorter than the associated "true" peak allele band, i.e., stutters are one repeat unit (allele value) less than the associated peak.…”

Section: Stuttermentioning

confidence: 99%

Probabilistic expert systems for handling artifacts in complex DNA mixtures

Cowell¹,

Lauritzen

Mortera

2011

Forensic Science International: Genetics

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This paper presents a coherent probabilistic framework for taking account of allelic dropout, stutter bands and silent alleles when interpreting STR DNA profiles from a mixture sample using peak size information arising from a PCR analysis. This information can be exploited for evaluating the evidential strength for a hypothesis that DNA from a particular person is present in the mixture. It extends an earlier Bayesian network approach that ignored such artifacts. We illustrate the use of the extended network on a published casework example.

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Interpreting simple STR mixtures using allele peak areas

Cited by 129 publications

References 7 publications

An investigation of the rigor of interpretation rules for STRs derived from less than 100 pg of DNA

An investigation of the rigor of interpretation rules for STRs derived from less than 100 pg of DNA

Forensic value of 14 novel STRs on the human Y chromosome

Probabilistic expert systems for handling artifacts in complex DNA mixtures

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