A comparison of stochastic variation in mixed and unmixed casework and synthetic samples

Bright, Jo‐Anne; McManus, Kurt; Harbison, SallyAnn; Gill, Peter; Buckleton, John

doi:10.1016/j.fsigen.2011.04.010

Cited by 32 publications

(9 citation statements)

References 10 publications

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“…This suggests that the use of serial dilutions is a reasonable approximation, which was also concluded in [34]. The exceptions are methods where both the extraction efficiency and the aliquot proportion are high, e.g.…”

Section: Resultssupporting

confidence: 54%

Characterization of degradation and heterozygote balance by simulation of the forensic DNA analysis process

2016

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Simulation experiments were used to show the impact of varying extraction efficiency, aliquot proportion, and PCR efficiency on the heterozygote balance of a range of diploid and haploid cells. Reducing either parameters introduces variance. It is well-known that the variance in heterozygote balance increases as the amount of DNA is reduced. Surprisingly the distribution is in fact diamond shaped — the variance start to decrease at very low amounts of DNA. Simulations suggest that pristine diluted DNA is an acceptable approximation in validations to infer heterozygote balance. However, the difference in distribution of the variance between diploid and haploid cell types may, under some circumstances, need to be considered in statistical models. Finally, we exemplify how simulations can be used to predict the outcome of PCR for degraded samples. Visualizing the predicted DNA profile as an electropherogram can help to identify the best approach for sample processing.Electronic supplementary materialThe online version of this article (doi:10.1007/s00414-016-1453-x) contains supplementary material, which is available to authorized users.

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Section: Resultssupporting

confidence: 54%

Characterization of degradation and heterozygote balance by simulation of the forensic DNA analysis process

2016

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“…• The composite method (Bright et al 2012, Pfeifer et al 2012 which provides that, for each locus, each allele considered responsive to predetermined acceptability criteria and observed in the replicates may contribute to a virtual composite profile, which consists of the sum of all observed alleles. This approach allowed the authors to partially reduce the drop-out phenomenon because all the alleles presented in the replicates were considered (Pfeifer et al 2012).…”

Section: Discussionmentioning

confidence: 99%

Infanticide in brown bear: a case-study in the Italian Alps – Genetic identification of perpetrator and implications in small populations

Davoli¹,

Cozzo²,

Angeli³

et al. 2018

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Sexually Selected Infanticide (SSI) is thought of as a male reproductive strategy in social mammalian species, because females who lose cubs may quickly re-enter oestrus. SSI has rarely been documented in non-social mammals and, in brown bears, SSI has been studied mainly in an eco-ethological perspective. The authors examined the first genetically documented infanticide case which occurred in May 2015 in brown bears in Italy (Trentino, Central-Eastern Alps). The infanticide killed two cubs and their mother. Hair samples were collected from the corpses as well as saliva, through swabs on mother’s wounds, with the aim of identifying the genotype of the perpetrator. The samples were genotyped by PCR amplification of 15 autosomal microsatellite loci, following the protocol routinely used for individual bear identifications within the Interregional Action Plan for Brown Bear Conservation in the Central-Eastern Alps (PACOBACE). Reliable genotypes were obtained from the mother, cubs and putative perpetrator. The genotypes were matched with those populating the PACOBACE database and genealogies were reconstructed. Both mother and perpetrator genotypes were already present in the database. Kinship analyses confirmed mother-cubs relationships and identified the father of the cubs. In this study, for the first time, the authors used the open-source LRmix STUDIO software, designed to analyse human forensic genetic profiles, to solve a case in wildlife. Through LRmix STUDIO, those alleles that do not belong to the victims were isolated and, finally, the perpetrator was identified. This study presents a method that allows, through the application of different models, the genetic identification of the conspecific perpetrator with the highest probability. The identification of the infanticidal male is relevant for the better management and conservation of wild populations with small effective population size (Ne) and low population growth rate, especially in the case of recently established populations in human-dominated landscapes. This procedure will have predictably wide applications, supplying important data in the monitoring of small and isolated populations.

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“…As might be expected from the nature of sampling variation, DNA extract sampling variation will have its largest relative effect on peak heights when the number of starting molecules of DNA is low. This effect has been shown in numerous graphs of Hb, measured over a range of average peak heights (APH) [16,22].…”

Section: Peak Height Variabilitymentioning

confidence: 77%

Validating multiplexes for use in conjunction with modern interpretation strategies

Taylor

Bright

McGoven

et al. 2016

Forensic Science International: Genetics

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In response to requests from the forensic community, commercial companies are generating larger, more sensitive, and more discriminating STR multiplexes. These multiplexes are now applied to a wider range of samples including complex multi-person mixtures. In parallel there is an overdue reappraisal of profile interpretation methodology. Aspects of this reappraisal include 1. The need for a quantitative understanding of allele and stutter peak heights and their variability, 2. An interest in reassessing the utility of smaller peaks below the often used analytical threshold, 3. A need to understand not just the occurrence of peak drop-in but also the height distribution of such peaks, and 4. A need to understand the limitations of the multiplex-interpretation strategy pair implemented. In this work we present a full scheme for validation of a new multiplex that is suitable for informing modern interpretation practice. We predominantly use GlobalFiler™ as an example multiplex but we suggest that the aspects investigated here are fundamental to introducing any multiplex in the modern interpretation environment.

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A comparison of stochastic variation in mixed and unmixed casework and synthetic samples

Cited by 32 publications

References 10 publications

Characterization of degradation and heterozygote balance by simulation of the forensic DNA analysis process

Characterization of degradation and heterozygote balance by simulation of the forensic DNA analysis process

Infanticide in brown bear: a case-study in the Italian Alps – Genetic identification of perpetrator and implications in small populations

Validating multiplexes for use in conjunction with modern interpretation strategies

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