by Mariah Jones
Technique Name: DNA Extraction
Fun Rating: 4/5
Difficulty Rating: 2/5
What is the general purpose?
The goal of DNA Extraction is to isolate DNA from the cells of a sample for later gene analysis.
Why do we use it?
DNA is typically found in the nucleus of eukaryotic cells or in the cytoplasm of prokaryotic cells. Many experiments, such as Next Generation Sequencing and qRT-PCR, require isolated and purified DNA. Therefore, DNA extraction is a useful tool to make the DNA accessible and usable for these experiments.
How does it work?
Depending on the starting sample, the steps for extraction may vary. However, there are three key steps that must occur in every extraction: lysis, precipitation, and purification. We can think of these steps as being similar to the steps we must take to make a sandwich.
Lysis: Lysis means “to burst”, and in DNA extraction, this step is meant to burst the cell walls and membranes. This step is typically carried out by adding a chemical that causes the cell membranes to rupture. Lysis is crucial to provide access to the DNA stored inside the nucleus or the cytoplasm of the cell. This step is similar to gathering ingredients to make a sandwich.
Precipitation: This step accomplishes two goals: maintaining the DNA structure (this structure of twists and bends is important for genetic coding) and separating that DNA from other proteins and lipids that were also within the cell. Typically this is done through chemical additions that separate the components based on their ability to dissolve in water. This step would be the equivalent to washing and preparing your veggies for your sandwich.
Purification: Once the DNA is isolated, the final step is to ensure the quality of the sample, to make sure we only have DNA and did not accidentally collect other proteins, called “impurities”, from the lysed cell. The different experiments that require DNA can be quite sensitive to any impurities present in the isolated DNA.
Purification is typically done using a spin column with a special filter. Only the DNA molecules will bind to the filter. This allows the scientist to wash away other impurities, before collecting the DNA from the filter. Therefore, purification of the DNA is necessary before using it in any of these downstream applications. Continuing the “sandwich” example, this step would be the assembly and plating.
These three steps are crucial to isolating DNA to be used for further analysis. However, various experiments or starting samples may require additional steps based on the specifics of its application. Many research labs even use manufactured kits to streamline these steps. Often, labs use purified DNA for sequencing to determine specific cancer diagnoses and identify other illnesses. The sequencing results can also be used to develop treatment plans or aid in pharmacology research developments. A lot of biology research relies on the use of extracted DNA. This simple technique serves as the backbone for most research labs and biomedical contributions made in the past 50 years.
