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The Process of eDNA

Detailed Description

The steps involved in eDNA analysis include:

  1. Sample collection- Samples are collected from water, soil, sediment or even from the air. Sample sizes may vary depending on the water body, purpose of the study, and other factors.
  2. Concentration- Target DNA in the environment is very sparse. Therefore, if you want to find what you are looking for, you need to cast a wide net. Much like throwing a fishing net into the water traps fish into a small space, concentration methods like filtration, centrifugation, or alcohol precipitation are used to collect a lot of DNA in a small volume. 
  3. DNA extraction - This process purifies the DNA in the sample for further analysis, separating it from everything else in the sample. This is typically done with commercially available DNA extraction kits that use basic chemistry principles to separate DNA from lipid membranes, proteins, and other cellular components. The extraction process can also remove things that can interfere with the PCR analysis such as humic acids or chlorophyll. 
  4. Amplification- A genetic marker needs to be amplified by qPCR to create a high quantity of DNA copies. DNA primers are matched with the DNA sequence and if the primers match, the chemical reaction will make numerous copies of that DNA. If they do not match, no copies are made.
  5. Quantitative PCR (qPCR) detection - a target sequence is detected with fluorescent signal amplification using probes to determine if the targeted species is present in the sample.


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