Characterisation of the Extent of Degradation of DNA & DNA Recovery from Hair Post Laundering and the Transfer (and Persistence) of Hair During Laundering and Social Interaction

Characterisation of the Extent of Degradation of DNA & DNA Recovery from Hair Post Laundering and the Transfer (and Persistence) of Hair During Laundering and Social Interaction

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qMost evidential DNA samples in forensic science have undergone some form of degradation before being presented for processing and analysis. This degradation can not only make the samples difficult or impossible to interpret but also lead to increased cost and the loss of time, effort and sample through processing of the samples via methods inappropriate for dealing with the degree of degradation present. Therefore a system to characterise the extent of degradation present in a sample prior to genetic analysis would be beneficial for the initial choice of an appropriate DNA processing method. A system for the characterisation of the extent of DNA degradation present in a sample was created using the Agilent 2100 Bioanalyzer to detect a change in peak height and/or morphology of three Alu regions of DNA based on the extent of degradation present. Creation of this system was based upon controlled degradation of samples via ultra violet irradiation. While the Alu/Bioanalyzer system showed some potential for providing a rough estimate of the amount of degradation present in a sample in terms of intact loci (or alleles present), the Bioanalyzer may not be a sensitive enough instrument to analyse highly degraded samples accurately. Additionally, testing of this system exposed a possible problem with characterising the degradation present in samples that have undergone degradation via some mechanism other than ultra violet irradiation. Of the fairly common evidentiary samples, hair is typically fairly robust and resistant to DNA degradation due to environmental insult. However, there are some possible pathways to degradation of the DNA present in hair. One of these possible avenues to degradation is laundering of hairs that may be adhered to clothing items. Laundering is a common way to remove other forms of evidence from clothing (such as stains) and may not only lead to degradation of the DNA of a hair but also may result in the transfer of a hair from one item of clothing to another when clothing items are laundered together or in the same laundering facility. This transfer may be important in attempting to determine which article of clothing the hair originated from. Transfer of hair is also important in social situations where many people are in close contact and innocuous hair transfer may confound hair transfer during a criminal event. This thesis also examined DNA extracted from hair post laundering and the transfer of hair during laundering and social interaction. While machine washing resulted in a significant loss of DNA, only some soaking conditions affected the amount of DNA extracted from laundered hairs and all soaked samples provided a complete or near complete genetic profile regardless of soaking conditions. Machine washing of hairs also resulted in a near equal distribution of hairs between two garments washed together regardless of length (or species) of hair although the morphology of human hairs appeared to have some affect on transfer outcome. Soaking of garments rarely resulted in the transfer of hairs between garments in these experiments. Preliminary experiments looking into hair transfer in social situations yielded insights into experimental design and suggested that hair transfer (and persistence of transferred hairs) is reasonably rare in most social situationsq--Abstract.Of the fairly common evidentiary samples, hair is typically fairly robust and resistant to DNA degradation due to environmental insult. However, there are some possible pathways to degradation of the DNA present in hair.


Title:Characterisation of the Extent of Degradation of DNA & DNA Recovery from Hair Post Laundering and the Transfer (and Persistence) of Hair During Laundering and Social Interaction
Author: Jennifer Christine Haeger
Publisher: - 2011
ISBN-13:

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