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How is Touch DNA Collected?

Published in Forensic Science 2 mins read

Touch DNA, also known as trace DNA, is collected when cells are left behind on surfaces through contact. This can happen through:

  • Touching: Simply touching an object can transfer skin cells.
  • Holding: Gripping an object leaves behind more cells.
  • Sneezing or Coughing: Droplets expelled during these actions can deposit DNA.

Touch DNA Collection Methods:

There are several methods used to collect touch DNA:

1. Swabs:

  • Cotton swabs: These are the most common method. They are moistened with a sterile solution and rubbed over the surface to collect DNA.
  • Nylon swabs: These are more effective at collecting DNA from porous surfaces like fabric.

2. Tape Lifting:

  • Adhesive tape: This method is used to collect DNA from smooth surfaces like glass or plastic. A piece of tape is pressed onto the surface and then removed, taking with it any trace DNA.

3. Vacuuming:

  • Vacuum cleaner: A specialized vacuum cleaner with a filter can collect DNA from large areas. This is often used in crime scenes.

4. Cutting:

  • Scissors or a knife: This method is used to collect DNA from fabric or other materials that can be cut. The cut portion is then analyzed for DNA.

Considerations for Touch DNA Collection:

  • Surface: The type of surface affects how much DNA is collected. Smooth surfaces like glass or plastic typically have less DNA than porous surfaces like fabric.
  • Time: The amount of DNA present on a surface decreases over time as it degrades.
  • Contamination: It is important to avoid contaminating the sample with DNA from other sources. This can be done by wearing gloves, using sterile equipment, and minimizing contact with the evidence.

Analyzing Touch DNA:

Once collected, touch DNA is analyzed in a laboratory using polymerase chain reaction (PCR). This process amplifies the DNA, making it possible to identify the individual who left the sample.

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