Morphological study of fragmented DNA on touched objects.

In recent years, forensic scientists showed that an individual's genetic profile can be retrieved from touched objects. Degraded DNA is believed to originate from epidermal cells and to be responsible for this phenomenon, yet the mechanism has not been confirmed. In the present study, we carried out a morphological and immunohistochemical investigation of nuclear DNA in differentiating keratinocytes in the skin and also a genetic analysis of DNA on swabs of human skin. Immunoelectron microscope analysis showed that single-stranded DNA was found both in the cornified layer of the skin and in swabs. Real-time-PCR assay proved that the DNA in the swabs was derived from the human DNA. Electron microscopic analysis of shadow-cast showed the presence of small DNA fragments in the swabs. It is conceivable that these DNA fragments on touched objects may originate from the epidermal cells of the cornified layer that are constantly sloughed off and leave for skin surface with sweat.

[1]  Jo-Anne Bright,et al.  Recovery of trace DNA and its application to DNA profiling of shoe insoles. , 2004, Forensic science international.

[2]  Peter M Schneider,et al.  STR genotyping and mtDNA sequencing of latent fingerprint on paper. , 2003, Forensic science international.

[3]  R. V. Oorschot,et al.  DNA fingerprints from fingerprints , 1997, Nature.

[4]  L. Goldsmith,et al.  Evidence that apoptosis and terminal differentiation of epidermal keratinocytes are distinct processes , 1999, Experimental dermatology.

[5]  Mauro Pesaresi,et al.  Fingerprints as evidence for a genetic profile: morphological study on fingerprints and analysis of exogenous and individual factors affecting DNA typing. , 2003, Journal of forensic sciences.

[6]  P. Wiegand,et al.  DNA typing of epithelial cells after strangulation , 1997, International Journal of Legal Medicine.

[7]  G. Tringali,et al.  Rapid and efficacious real-time quantitative PCR assay for quantitation of human DNA in forensic samples. , 2004, Forensic science international.

[8]  H. Willard,et al.  Structure, organization, and sequence of alpha satellite DNA from human chromosome 17: evidence for evolution by unequal crossing-over and an ancestral pentamer repeat shared with the human X chromosome , 1986, Molecular and cellular biology.

[9]  H. Takahashi,et al.  Translocation of profilaggrin N-terminal domain into keratinocyte nuclei with fragmented DNA in normal human skin and loricrin keratoderma. , 1998, Laboratory investigation; a journal of technical methods and pathology.

[10]  Jerilyn A. Walker,et al.  Human Genomic DNA Quantitation System, H‐Quant: Development and Validation for Use in Forensic Casework , 2007, Journal of forensic sciences.

[11]  David B. Williams,et al.  Transmission Electron Microscopy , 1996 .