Week 3 started off with a mouse dissection. It was both fascinating and a little gross. I saw exactly how to collect different types of cells from organs. For example, bone marrow cells are washed out with a needle from the mouse’s femur, and spleen and liver cells are pressed out from their respective organs. After collecting these cells, the cells are washed to remove anything that we don’t want. The next step would be to analyze them using flow cytometry, which is away to count and study different types of cells in a sample. Flow cytometry is like a scanner that tells you exactly how many cells there are.
I also learned about picking bacterial colonies. Basically, bacteria grow in tiny clusters on plates, and the goal is to pick the ones that are most isolated so you know exactly what you’re working with. Using a pipette tip, you gently touch a single colony and transfer it into a small tube with liquid media. This tube then goes into a shaker set to 37 degrees Celsius at 220 rotations per minute. The shaking helps the bacteria mix with the liquid, giving them oxygen and nutrients so they can grow overnight.
By day six, it was time to expand the plasmids we were working on. The first step is to take the small liquid cultures we grew in the shaker overnight and pour them into a bigger flask with LB broth. LB broth is basically a nutrient-rich soup that bacteria love to grow in, and it has to be autoclaved, which is away of sterilizing it so no other bacteria sneak in. The flask goes back into the shaker overnight at the same temperature and speed (37 degrees Celsius at 220 rotations per minute), giving the bacteria room to multiply and produce lots of copies of the plasmid.
Once the bacteria had grown, I used a midiprep kit to extract the plasmid DNA. This kit has step-by-step instructions that allow you to isolate the plasmid from all the other bacterial material. After the midiprep, I had my plasmid DNA stored in the freezer overnight so it would stay stable until I was ready to use it.
The next day, it was time to measure the DNA concentration using a Nanodrop. This machine can take just a tiny drop of your sample and tell you how much DNA is in it, usually measured in nanograms per microliter. Knowing the concentration is important because when you set up experiments like PCR, you need precise amounts of DNA.
After PCR, we ran another gel electrophoresis to see if the DNA had copied correctly. Unfortunately, this one didn’t go smoothly. The gel results were messy, with too many bars in places where there shouldn’t have been any, and some of it looked smeared. It was a little frustrating at first, but honestly, this is all part of learning how experiments work in real life.
Picking colonies, watching cells under flow cytometry, expanding plasmids, and troubleshooting PCR gels are all steps that seem small on their own, but they build up to the bigger goal of understanding how genes and proteins work. It’s also a reminder that science doesn’t always go perfectly the first time, and that’s okay. Each failure is a chance to understand the process better and improve your technique.
I’ll be back next week!
