The Science Behind: Forensics (Part 2)

In my last article, we talked about Forensics. Today, I want to highlight an important tool of forensics: DNA.


Before starting, here’s a quick refresher on what DNA is. DNA, or deoxyribonucleic acid (a mouthful, I know), is the carrier of genetic code inside our bodies. Another way to think of it would be a giant instruction manual specifically made for each individual organism. Every living thing has DNA inside it, making it a useful tool in forensic investigations.


Now to the fun part. Why is DNA so important in forensics? Since DNA is unique to each individual, it’s used to identify suspects. For example, hair strands, saliva, and even skin cells under someone else’s fingernails from an altercation all contain DNA. When forensics experts and law enforcement show up to a crime scene, they collect DNA. Swabbing, articles of clothing, and things that people would have touched are all considered evidence for the investigation, because they can contain skin cells, fingerprints, and strands of hair.


The next step would be to run the DNA against the existing database to see what comes up as a match. Often, labs have access to a database with the DNA of many other individuals. Once the DNA is extracted from the evidence, it’s entered into the database to see who it matches with. From there, it’s just a matter of bringing in your suspect and solving the crime.


So that’s it. The involvement of DNA in forensics is pretty simple. Collect evidence, extract DNA, run it against the database, and find a match. But one thing that caught my eye was the extraction process. DNA molecules are minuscule, so extracting them is hard work. How do they do it?


The first step is to break the cells that contain the DNA. I won’t go too deep into this since cell structure is complicated, but in a cell, there are many parts. One of those parts contains DNA, and breaking the cell is the first step to pulling that part out. The next step is to separate the DNA from everything else that was pulled out. Rubbing alcohol is added to the DNA (which is insoluble in alcohol) and the DNA solidifies. Once we have our DNA, it’s ready to be cleaned and checked against the database.


If you’re curious about how to extract DNA, I encourage you to try this experiment. It has a really easy guide on how to extract the DNA of a strawberry, and you can get firsthand experience of the DNA extraction process right from the comfort of your own home.


Sources:

Science Learning Hub - DNA Extraction

BBC Bitesize - What is DNA?

AZO Life Sciences - Role of DNA in Forensic Science


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