Cheeky Year 9 microscopy

Do you look at cheek cells with Year 9? It never works, right? Oh, alright, I know there’s some disagreement on this. Bill swears it works every single time. I, on the other hand, have never, ever, ever found even a single cheek cell from the usual SwabYourInnerUpperCheekWithACottonBud technique. Seriously, not one. Even when rigorously following the Burnett Protocol. I had pretty much given up on it. After all, there are so many more interesting, findable cells out there – all the protoctists, sperm cells (no, not what you think – we get them from a cattle breeding centre), and so on. On the other hand, apart from red blood cells, it’s about the only cell of theirs they get to see, and there’s something quite soulful about watching a cluster of you slowly dying on a slide… and reflecting that that tiny dark blue smudge contains all the information needed to make another you.

So, what to do? Well, we carry out PCR with our Year 13s and after mixed results with eyebrow hair root cells, we got spectacular improvement with cheek cells obtained with a saline rinse. And it struck me, hey, look at that cell pellet in the centrifuge tube! It must be full of….. 5 minutes later, I was looking at ridiculous numbers of cheek cells under the microscope. 70 in a single HP view. Over 1000 in a single MP view. Lovely great plump juicy obvious unmissable clumped cheek cells. No more fruitless hunting around a slide!

And it was great. The Year 9s were slightly put off by the saline rinse, but gamely went for it. I encouraged really vigorous rinsing for one minute, accompanied by scraping the inside cheeks with their teeth. Three 60 second twirls in the mini-centrifuge gave a huge cell pellet. Extract it with the end of a split spill (makes a nice little paddle for scooping it up), on to slide, stain, and there are actually so many cells that you have to gently squish them flat with the cover slip. Highly recommended.

And relentlessly pursuing my objective of making my students do all the work, I came up with this idea for covering Krebs cycle. This can be rather dry, even with the wonderful John Kyrk website animations, so what can you do? Well, how about getting them to interpret the results, just as we do for Calvin’s results on Light Independent reactions? I’ve attached the exercise – let me know what you think!

That’s it for now. Have a great week!

Paul

Unravelling metabolic pathways a la Hans Krebs

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