Morphological study of fragmented DNA on touched objects

Area of Science:

• Forensic Science
• Molecular Biology
• Dermatology

Background:

• Genetic profiling from touched objects is a growing area in forensic science.
• The source of degraded DNA on surfaces, suspected to be epidermal cells, remains unconfirmed.
• Understanding DNA transfer mechanisms is crucial for forensic trace evidence analysis.

Purpose of the Study:

• To investigate the morphological and immunohistochemical characteristics of nuclear DNA in human skin keratinocytes.
• To genetically analyze DNA found on skin swabs.
• To elucidate the mechanism of DNA deposition on touched objects.

Main Methods:

• Immunoelectron microscopy was used to analyze nuclear DNA in differentiating keratinocytes and on skin swabs.
• Real-time PCR assays were performed to confirm the human origin of DNA from swabs.
• Shadow-cast electron microscopy was employed to analyze the physical state of DNA fragments.

Main Results:

• Single-stranded DNA was detected in the skin's cornified layer and on swabs.
• Real-time PCR confirmed that DNA on swabs originated from human sources.
• Electron microscopy revealed the presence of small DNA fragments in the swabs.

Conclusions:

• The study provides evidence that degraded DNA on touched objects likely originates from epidermal cells shed from the skin's surface.
• These findings support the hypothesis that sloughed keratinocytes, along with sweat, contribute to DNA deposition on environmental surfaces.
• This research enhances the understanding of DNA transfer in forensic contexts, particularly concerning touch DNA evidence.