It’s all in the genes at Dr. T’s Honors And AP Biology classes these days. Biology Honors students learned how to extract DNA from strawberries using a technique modified from Avery’s Nobel Prize experiments. In a nutshell, students broke apart cellular and nuclear membranes of plant cells using a detergent and “coagulated” proteins with salt. They then precipitated out DNA in spools using 91% isopropanol and stored their loot for show-and-tell. While strawberries hardly qualify as criminal suspects, this technique is widely used in Forensics laboratories all over the world. Even better, it is fun!
Meanwhile, AP Biology students learned how to analyze DNA using agarose electrophoresis. Sample DNA was obtained from Bacteriophage Lambda (a virus that infects bacteria) and digested with enzymes called Restriction Endonucleases that cleave DNA at specific sites. What is shown on gels is a ladder of fragments we refer to as a “ fingerprint”. These enzymes were first isolated from bacteria after it was discovered that they defend themselves from viral infection by cleaving viral DNA. The enzymes used in lab were PstI, EcoRI and HindIII and all are commonly employed in Forensics and Biotechnology. The next step for the AP students is a Whodunit Mystery where they will use this technology to identify the perpetrator of a crime using DNA obtained from the mock crime scene.
