If you've never done a DNA extraction lab, then this one is an absolute MUST try!
DNA, DNA, DNA. D-N-A, the famous DNA. What is a science class without a DNA extraction experiment? You’ll be surprised how many students have never done this in their science classes. I love this experiment using strawberries, best. There are other foods that can be used to extract DNA from, like bananas, I just prefer using strawberries. Strawberries are octoploids, meaning they have 8 copies of their chromosomes! So, strawberries yield a lot of DNA! Bananas are triploids, meaning they have 3 copies of each of their chromosomes.
Some DNA extraction labs use saliva as the extraction source. Yes, you heard right, students extract DNA from their own saliva. I have never tried this lab with my classes because I just never liked the idea of 30 plus kids spitting in my class (It’s the germ-a-phobic in me.). So, while I have never tried this lab, it might be one you may consider trying out. I guess the neat thing about DNA Saliva lab is students will get to see their own DNA.
For me personally, I felt like strawberries were cleaner to do in class and the easy way to go 😊…and I also noticed middle school students loved to mash them (which is a step in the lab). Just be sure they don't mash too hard. Some rough mashers will mash more than just the strawberries. They’ll accidently mash the bag too, making a hole in it. This is when strawberry juice is likely to go flying all over and can stain a shirt or two.
Yes, I was once the lucky person who once got splashed with one of my great masher’s strawberry juice. And of course, I wore a white blouse that day. Yeah. After that, I decided a red shirt was best to wear on that particular lab day in the future. No more white attire. So, be sure to warn students not to be too rough with their mashing- and be sure to use the thicker plastic bags for this lab, as they are more durable than the less expensive thin ones.
But, yes, students enjoy this part of the lab-it’s like playing with food (of course not one they will eat in this case) and it is cool when they finally get to see actual, real life DNA at the end of the experiment. DNA in a cell's nucleus is microscopic. Students find it cool that they get to see the DNA strands come together and clump up to a point where they can actually see it without a microscope. Even for me, the first time I did this lab with my classes, I must admit; I was very intrigued. I still love doing this lab, even though I have done it many times, because every time there is one or two that come out really good, and it is always fun to see. After the cold alcohol is poured in the test tube, and the DNA clump together, students can take a Q-tip and use the plastic end of it to gently pick up the DNA and take it out to get a closer look at its beautiful, double helix shape.
If you would like instructions for this lab, you can search it up online, or check out my free digital download: Strawberry DNA Lab PowerPoint/PDF that is in my store. I created this instructional PDF to help make the lab go smoothly for first timers. It includes step-by-step instructional pages, helpful and tried tips, and pictures. It also has a few post lab questions that you can have your students answer after doing the experiment. If you try this lab out- I hope you have a biology-buzzed fun time!
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