Single source DNA profile recovery from single cells isolated from skin and fabric from touch DNA mixtures in mock physical assaults

DNA mixtures are a common source of crime scene evidence and are often one of the more difficult sources of biological evidence to interpret. With the implementation of probabilistic genotyping (PG), mixture analysis has been revolutionized allowing previously unresolvable mixed profiles to be analyzed and probative genotype information from contributors to be recovered. However, due to allele overlap, artifacts, or low-level minor contributors, genotype information loss inevitably occurs. In order to reduce the potential loss of significant DNA information from donors in complex mixtures, an alternative approach is to physically separate individual cells from mixtures prior to performing DNA typing thus obtaining single source profiles from contributors. In the present work, a simplified micro-manipulation technique combined with enhanced single-cell DNA typing was used to collect one or few cells, referred to as direct single-cell subsampling (DSCS). Using this approach, single and 2-cell subsamples were collected from 2-6 person mixtures. Single-cell subsamples resulted in single source DNA profiles while the 2-cell subsamples returned either single source DNA profiles or new mini-mixtures that are less complex than the original mixture due to the presence of fewer contributors. PG (STRmixTM) was implemented, after appropriate validation, to analyze the original bulk mixtures, single source cell subsamples, and the 2-cell mini mixture subsamples from the original 2-6-person mixtures. PG further allowed replicate analysis to be employed which, in many instances, resulted in a significant gain of genotype information such that the returned donor likelihood ratios (LRs) were comparable to that seen in their single source reference profiles (i.e., the reciprocal of their random match probabilities). In every mixture, the DSCS approach gave improved results for each donor compared to standard bulk mixture analysis. With the 5- and 6- person complex mixtures, DSCS recovered highly probative LRs (> 1020) from donors that had returned non-probative LRs (<103) by standard methods.

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Touch DNA; A Quantitative Study in the Perspective of Forensic Science

Austin Journal of Forensic Science and Criminology ◽

10.26420/austinjforensicscicriminol.2021.1084 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Avinash Kumar ◽

Keyword(s):

Forensic Science ◽

Quantitative Study ◽

Research Work ◽

Smart Phone ◽

Physical Contact ◽

Rt Pcr ◽

Touch Dna ◽

Dna Profile ◽

Cutting Out ◽

Method Of Extraction

“Touch DNA” is a DNA obtained from biological material transferred from a source to an object or a person during physical contact. Touch DNA came into notice after the research work of Ronald van oorschot, he focused on DNA from fingerprint. We usually use the “Swabbing” and “cutting out” Technique for collection of Touch DNA. Organic method of extraction is most favoured, followed by RT-PCR for quantitation of DNA. Belonging’s used in day-to-day life holds an ample amount of DNA like Brush, Smart phone, Mask, Toothpicks etc, which is quite sufficient to generate a DNA profile of any individual. It can be a very valuable source to establish the identity and individuality of any person in the field of forensic science.

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Analysis of red autofluorescence (650-670nm) in epidermal cell populations and its potential for distinguishing contributors to 'touch' biological samples

F1000Research ◽

10.12688/f1000research.8036.1 ◽

2016 ◽

Vol 5 ◽

pp. 180 ◽

Cited By ~ 6

Author(s):

Cristina E. Stanciu ◽

M. Katherine Philpott ◽

Eduardo E. Bustamante ◽

Ye Jin Kwon ◽

Christopher J. Ehrhardt

Keyword(s):

Dna Extraction ◽

Epidermal Cell ◽

Biological Samples ◽

Cell Populations ◽

Dna Mixtures ◽

Touch Dna ◽

Intrinsic Factors ◽

Significant Challenge ◽

Front End ◽

Distinct Cell

Interpretation of touch DNA mixtures poses a significant challenge for forensic caseworking laboratories. Front end techniques that facilitate separation of contributor cell populations before DNA extraction are a way to circumvent this problem. The goal of this study was to survey intrinsic fluorescence of epidermal cells collected from touch surfaces and investigate whether this property could potentially be used to discriminate between contributor cell populations in a biological mixture. Analysis of red autofluorescence (650-670nm) showed that some contributors could be distinguished on this basis. Variation was also observed between autofluorescence profiles of epidermal cell populations from a single contributor sampled on different days. This dataset suggests that red autofluorescence may be a useful marker for identifying distinct cell populations in some mixtures. Future efforts should continue to investigate the extrinsic or intrinsic factors contributing to this signature, and to identify additional biomarkers that could complement this system.

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Effects of carbamylcholine on chick embryo aggregate retina cell cultures

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100103814 ◽

1988 ◽

Vol 46 ◽

pp. 350-351

Author(s):

Glenn M. Cohen ◽

Radharaman Ray

Keyword(s):

Cell Cultures ◽

Single Cells ◽

Retinal Cell ◽

Cell Aggregates ◽

High Concentration ◽

In Ovo ◽

Sterile Culture ◽

Retinal Tissue ◽

Synaptic Junctions ◽

And Control

Retinal,cell aggregates develop in culture in a pattern similar to the in ovo retina, forming neurites first and then synapses. In the present study, we continuously exposed chick retinal cell aggregates to a high concentration (1 mM) of carbamylcholine (carbachol), an acetylcholine (ACh) analog that resists hydrolysis by acetylcholinesterase (AChE). This situation is similar to organophosphorus anticholinesterase poisoning in which the ACh level is elevated at synaptic junctions due to inhibition of AChE, Our objective was to determine whether continuous carbachol exposure either damaged cholino- ceptive neurites, cell bodies, and synaptic elements of the aggregates or influenced (hastened or retarded) their development.The retinal tissue was isolated aseptically from 11 day embryonic White Leghorn chicks and then enzymatically (trypsin) and mechanically (trituration) dissociated into single cells. After washing the cells by repeated suspension and low (about 200 x G) centrifugation twice, aggregate cell cultures (about l0 cells/culture) were initiated in 1.5 ml medium (BME, GIBCO) in 35 mm sterile culture dishes and maintained as experimental (containing 10-3 M carbachol) and control specimens.

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Selective Staining of Acid Mucopolysaccharides By Ruthenium Red

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100099933 ◽

1968 ◽

Vol 26 ◽

pp. 38-39

Author(s):

J. H. Luft

Keyword(s):

Electron Microscope ◽

Light Microscopy ◽

Light Microscope ◽

Osmium Tetroxide ◽

Single Cells ◽

Ruthenium Red ◽

Collagen Fibers ◽

Selective Staining ◽

Pectic Substances ◽

Solid Tissues

Ruthenium red is one of the few completely inorganic dyes used to stain tissues for light microscopy. This novelty is enhanced by ignorance regarding its staining mechanism. However, its continued usefulness in botany for demonstrating pectic substances attests to selectivity of some sort. Whether understood or not, histochemists continue to be grateful for small favors.Ruthenium red can also be used with the electron microscope. If single cells are exposed to ruthenium red solution, sufficient mass can be bound to produce observable density in the electron microscope. Generally, this effect is not useful with solid tissues because the contrast is wasted on the damaged cells at the block surface, with little dye diffusing more than 25-50 μ into the interior. Although these traces of ruthenium red which penetrate between and around cells are visible in the light microscope, they produce negligible contrast in the electron microscope. However, its presence can be amplified by a reaction with osmium tetroxide, probably catalytically, to be easily visible by EM. Now the density is clearly seen to be extracellular and closely associated with collagen fibers (Fig. 1).

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Fluorescent potentiometric dyes for membrane-potential imaging

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100168566 ◽

1994 ◽

Vol 52 ◽

pp. 166-167

Author(s):

Leslie M. Loew

Keyword(s):

Membrane Potential ◽

Single Cells ◽

Quantitative Imaging ◽

Optical Recording ◽

Biological Processes ◽

Major Focus ◽

The Past ◽

Excitable Systems ◽

Major Application ◽

The Impact

A major application of potentiometric dyes has been the multisite optical recording of electrical activity in excitable systems. After being championed by L.B. Cohen and his colleagues for the past 20 years, the impact of this technology is rapidly being felt and is spreading to an increasing number of neuroscience laboratories. A second class of experiments involves using dyes to image membrane potential distributions in single cells by digital imaging microscopy - a major focus of this lab. These studies usually do not require the temporal resolution of multisite optical recording, being primarily focussed on slow cell biological processes, and therefore can achieve much higher spatial resolution. We have developed 2 methods for quantitative imaging of membrane potential. One method uses dual wavelength imaging of membrane-staining dyes and the other uses quantitative 3D imaging of a fluorescent lipophilic cation; the dyes used in each case were synthesized for this purpose in this laboratory.

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Dem Täter auf der Spur – Nachweis von Körpersekreten mittels mRNA-Profiling

Praxis ◽

10.1024/1661-8157/a002233 ◽

2016 ◽

Vol 105 (2) ◽

pp. 79-84

Author(s):

Cordula Haas ◽

Adelgunde Kratzer

Keyword(s):

Dna Profile ◽

Mrna Profiling

Zusammenfassung. Bis anhin erfolgt die Spurenartbestimmung von Körpersekreten mit enzymatischen und immunologischen Tests, die aber zum Teil nicht sehr spezifisch sind. mRNA-Profiling ist eine vielversprechende neue Methode zum Nachweis von Körperflüssigkeiten (vor allem Blut, Speichel, Sperma, Vaginalsekret und Menstrualblut), bei der die Expression sekretspezifischer Proteine untersucht wird. Mit einer RNA/DNA Co-Analyse aus derselben Probe kann sowohl das Körpersekret identifiziert werden, als auch mittels DNA-Analyse die Probe einer Person zugeordnet werden. Diese Methoden und Ergebnisse werden anhand eines Kriminalfalls erklärt. In der Schweizerischen DNA-Datenbank werden die DNA-Profile von Spuren und tatverdächtigen Personen erfasst und verglichen. Eine Übereinstimmung der DNA-Profile ist ein belastendes Beweisstück gegen den Tatverdächtigen, muss aber vom Gericht zusammen mit anderen Untersuchungsergebnissen abschliessend beurteilt werden.

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