Bigfoot DNA and Trace Evidence: Understanding the Basics

https://www.youtube.com/watch?v=tst15giw67c&t=420s

Today, we're diving into the world of DNA and trace evidence in forensic science. Trace evidence refers to tiny particles like hair, pollen, and fibers that are often invisible to the naked eye, excluding DNA. "Trace DNA" and "touch DNA" are clarified, with "trace DNA" being the correct term for small amounts that can transfer with minimal contact.

Challenges in collecting DNA from hair without roots, especially for species identification, are discussed, along with factors concerning the degradation of DNA, such as water, sun exposure, and chemical treatments.

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Study Guide for Collecting eDNA from Soil
Materials Needed:

1. Sterile gloves
2. Sterile sampling tools (e.g., spatulas, spoons)
3. Sterile collection tubes or bags
4. Dry silica gel packs
5. Labels and markers
6. Sterile water (optional, for moistening dry samples)
7. Cooler with ice packs (for transport)
8. Field notebook or electronic device for recording data
Collection Procedure

Preparation:

• Wear sterile gloves to avoid contaminating the samples.
• Sterilize all sampling tools if they are not pre-sterilized.
• Label each collection tube or bag with relevant information (e.g., date, time, location, sample ID).

Sample Collection:

• Identify the sampling locations. Ensure that each location is adequately documented in your field notebook.
• Using a sterile tool, collect soil from the surface and, if needed, from different depths.
• For each sample, collect about 10-20 grams of soil. This amount can vary based on the specific requirements of your analysis.
• Place the soil sample into the sterile collection tube or bag. Seal it immediately to prevent contamination.
 
Using Dry Silica Packs:

• Add a dry silica gel pack to each collection tube or bag containing the soil sample. Silica gel packs help to absorb moisture, preserving the DNA in the sample.
• Ensure that the silica gel pack does not come into direct contact with the soil, if possible, to prevent any potential contamination or interference with the DNA.

Transportation and Storage:

• Keep the collected samples cool by storing them in a cooler with ice packs during transportation. This step is crucial to prevent DNA degradation.
• Once in the lab, store the samples in a cool, dry place. For long-term storage, it is recommended to keep the samples at -20°C or lower.
• Ensure that the samples remain dry during storage. Check the silica gel packs regularly and replace them if they become saturated with moisture.

Documentation:

• Record all relevant details of the collection process, including the location, environmental conditions, and any observations that may affect the sample quality.
• Maintain a chain of custody log to track the handling and storage of each sample from collection to analysis.