And it’s back to my old favourite, Lego.
My Year 11s meet Lego as a way of understanding the link between DNA and proteins, and how the same amino acids can make different proteins depending on what instructions are being followed. See this Burble from a long time ago.
At A-level, of course, this is all covered in much more detail, but you still need some kind of fun activity to break up the theoretical background and help them visualise/conceptualise the different ideas.
I start by showing them a simple Lego model.
What might this represent?
DNA! announces someone, engaging mouth before brain.
OK, so right idea that it’s some kind of molecule, but why can’t it be DNA?
They see that it has more than 4 types of monomer.
This time we arrive at protein. We revise amino acids, peptide bonds and so on.
OK, so it’s a protein, and you’ve just eaten it for lunch. What happens to it?
They rummage through their brains for some Year 9 digestion memories…. oh yes, it gets broken down…by proteases… so it can be absorbed… into the bloodstream…
We add some A-level detail – the peptide bonds are hydrolysed – but then, key question:
Where do they go?
This takes them a little longer. Go? What do you mean? But eventually they work out that the amino acids are being delivered, by the bloodstream, to cells all over the body.
Right! And what do the cells use them for?
Again, they can be pleasingly perplexed by this. It usually needs a prompt or two.
What can cells make out of amino acids?
Once they’ve worked out the answer, there’s a bit more A-level revision on the kind of proteins that might be made – channel proteins, protein pumps, ATP synthase, hair (for those lucky enough to possess hair making cells), ENZYMES!, hormones, mucus, collagen, haemoglobin – hurrah, they’re on a roll!
Right. And where does this happen? And how will all these proteins be different? So how does the ribosome know which order to put the amino acids in?
By now, they’re happy and confident and make the link to the genetic information in the nucleus. We quickly revise the basic principles of transcription and translation and why they’re necessary…
So! One half of the lab becomes the nucleus, with some chromosomes… (there’s a set for each team).
The other half of the lab becomes the cytoplasm, with some ribosomes… (again, a set for each team).
And a great pile of communal amino acids…
And in teams of two, they become RNA polymerase/mRNA, in a race to find the gene (they look for a Start codon on Chromosome 7), transcribe it (on a rough piece of paper) into mRNA until they hit a Stop codon, and then sprint to the ribosome to translate their copy into a colour-coded polypeptide…
It’s great. They have to think, they have to work together and communicate, they correct each other (if one forgets to turn T into U, for example), they have to apply their understanding, and it’s competitive!
One by one they bring me their completed polypeptides. Can you see which pair were given some mutated DNA….?
Lots of discussion points here. mRNA on a bit of scrap paper? That’s right – it’s short lived and disposable. Trade off for cell? Need to do it quickly, but need to do it accurately. Fast and you out compete other cells. But incorrect, and mutations can be disastrous…
And so on.
Half term tomorrow. Can’t wait. Have a good one!