Monthly Archives: March 2016

Appy Olidays

Last burble of the Spring term 2016. And a very brief one, as I wrestle with the logistics of the last ever OCR PSAs for A-level (good riddance!) whilst also trying to fit in what’s left of the AS specification with only 4 weeks before study leave. Gulp.

So, here’s an app recommendation for all you ipad users out there.

It was one of those happy accidents. I was looking for an entirely different app – something called Fly Lab which was a superb interactive website for trying out Drosophila crosses, and which I was convinced must have been turned into an app. Alas, it hasn’t, but as I worked through a variety of search terms on the App Store, I stumbled upon…

pigeonetics-front

Developed by the learn.genetics people at Utah university, it’s free and fantastic. Students are introduced to pigeon breeding and have to produce “target” birds with specific combinations of phenotypic features, by selecting parent  birds from a variety of possible genotypes/phenotypes.

It starts easily – target bird: male.

And so they learn about the homogametic nature of male birds – ZZ.

Then a female bird. ZW. Heterogametic.

It rapidly gets more complicated, but you can see the set up below. You choose two parent birds from the ones sitting on the wire at the top. It shows both their phenotype and relevant genotype. Having selected the birds, you then select which alleles you want in your offspring. Then you press Hatch!

pigeon

It’s perfect for Year 11 students as either a revision game or an extension challenge. Even if they don’t get the finer details, the basics of diploid organisms contributing one allele each to their offspring couldn’t be clearer. There’s basic dominant/recessive alleles of a single gene, but there are plenty of multiple alleles kicking around, along with sex linkage and epistasis. My students absolutely loved it.

PS – you can also just play it from the learn genetics website – book your ICT suite and get stuck in!

http://learn.genetics.utah.edu/content/pigeons/pigeonetics/

Wishing you all a very happy and restful Easter holidays.

success

Advertisements

You win some…

Last week I described a successful interview lesson and how it evolved over time. This week I’m going to tell you about another interview lesson, only with a different outcome. Before I do that, here’s a photo of the Year 10 Fast Plants…

IMG_1165

All planted from seed at exactly the same time on exactly the same day in exactly the same conditions. But one lot has been on the window sill, and one lot has been under the light bank. No prizes for guessing which is which, but as well as the obvious conclusions about plant growth and light,  it’s a good exercise for making them think about what they could measure, to make a quantifiable comparison, which they can then link to the difference in treatment.

It’s also a great counter to the nutritionist who believe that there is enough energy in a seed to produce a full grown plant…

Anyway, it’s been an interesting few weeks. I’ve been applying for jobs and have now triumphantly completed a Hat Trick of Rejections. The first two I realised I didn’t particularly want, but you still want to be the one who makes that decision. It’s like when you’re a teenager and you hear that the girl/boy you don’t fancy also doesn’t fancy you. You feel strangely hurt in a completely unreasonable and illogical sort of way.

But the third one I was very keen on. I liked the school, the students, the location, the contract. And I had to teach a lesson to Year 12 on Classification, 5 Kingdoms, 3 domains, and the link between Phylogeny and Classification. In 35 minutes.

So, where to start? I wanted to review their knowledge/understanding of the 5 Kingdoms which they ought to have done at GCSE. A party game? That one where you put a post-it on people’s foreheads and they have to ask questions to figure out who they are? I quickly realised that wouldn’t work – they could simply “get it” by looking at what other people had, rather than asking the kind of questions I wanted to elicit. Quick fire question and answer review? Bit predictable, bit boring… After all, I’m trying to sell myself here, I need to flag up some of my skills…

… but it’s also really important that THEY do something. Figure something out for themselves. What could this be? Well, maybe after reviewing the 5 Kingdoms they could carry out Woese’s analysis themselves? I spend a long time researching this – data on ssrRNA is hard to find – a friend suggests it’s because the key sequences are on different parts of the gene – but I find out all kinds of other really interesting molecular details.

Could they use this to form a classification? And when they’ve done that, could we use it build a phylogeny?

It’s falling together. I have that nice, warm feeling in my tummy which tells me I’ve got something that will work.

So I put it all together, starting with this…

Classification lesson March 2016

I hope the hyperlinks survive the journey to WordPress!

The idea is that a student selects a colour, any colour. Chance for a bit of banter. Why green? Favourite colour! Why red? Support Liverpool? No? Just like red. OK.

Clicking on the coloured oval takes you to a blank slide. Ask the question – I’m thinking of a type of organism. Here come some clues. Let me know when you can identify it. Then just press the forward arrow.

First clue: cellular. Does that help? No. All organisms are cellular. Does it exclude anything? They might suggest viruses.

Next clue will depend on the organism, but let’s say the student chose red. Second clue is: Cells have internal membranes. Does this help? Ah, now they can exclude the prokaryotes. They know it’s not a bacterium.

Third clue is: Cells have Cell Walls. Does that help? They may jump in with, “It’s a Plant!” Is it? Are you sure? A bit of thought and they realise they can eliminate Animals, but not Fungi or Plants.

Fourth clue is: Sessile. We talk a bit about how this is a really unhelpful feature. It hasn’t moved us on at all.

The fifth clue nails it: Autotrophic. It has to be a Plant.

A final click brings up: Anything else? What else can they tell me about plants? Maybe the cell wall? Right, it’s made of cellulose. And so on.

At this point, click on the smiley green face. It takes you to a picture of an oak tree. Make the point that they didn’t need to see the oak tree to know that it was a plant – they just needed one of its cells…

Clicking on the picture of the oak tree should take you back to the first slide, where the red oval will disappear. Time to pick another.

When they’ve finished these – which will give them Plants, Animals, Fungi and Bacteria – a click from Slide 1 takes them to a picture of a Euglena. What could this be? Any suggestions? Ask some questions! It’s green, which suggests plant. But it hasn’t got a cell wall, which suggests animal. It’s single celled which suggests bacterium, but it’s clearly got internal organelles, so it must be Eukaryote. They will probably recall Protoctista. An Amoeba on the next click reinforces the point that this isn’t a very helpful grouping. What’s so special about being single celled? An Amoeba is an animal in everything but multi-cellularity! And, actually, interestingly, a Euglena has chloroplasts with 3 membranes + thylakoids, which suggests interesting things about its origins (I don’t get round to this in the lesson, but it’s a nice detail to have up your sleeve).

The next slide shows all the organisms in a row. It’s the 5 Kingdoms (my son, Peter, on a water slide, illustrating the Animals). Further clicking reveals their cells. I reiterate: if you know the cell, you know the Kingdom.

The next slide, blank blue, indicates a break in the Powerpoint. Time for them to do some work!

So if we’re comparing organisms at the cellular level, what other points of comparison are there? Apart from being cellular, what do all organisms share? They quickly get DNA, followed by ribosomes and RNA. Which they must have if they’re to make proteins. And how might these vary? We talk about base sequences.

Then I hand out the data table.

Woese classification lesson

As I suspect, this exercise takes them barely 5 minutes, but they’ve grouped 6 unknown organisms into 3 groups. Based on RNA and ribosomal data. Excellent.

On the board, I write LUCA. One of them has heard of the Last Universal Common Ancestor. So how does the family tree look? The line comes up, and then branches. Before the line, what do they all share? AUG as a start codon. But the branch represents an evolutionary innovation. What could have happened? There’s a choice, but maybe it’s the TATA box, or a switch from Formyl-methionine to Methionine. It doesn’t matter. One group (E) goes one way, everything else goes the other way.

And then, at some point, it branches again. A new size of ribosome? More polypeptides in the RNA polymerase? Again, it doesn’t matter, but you now have 2 more groups on two separate branches, sharing a single common ancestor. C on one branch, and A, B, D and F on the other.

Time to break the code. What are these organisms? Back to the Powerpoint and there’s a picture of some Archaea in their pretty thermophilic environment. Because E are the bacteria, C are the Archaea, and A, B, D and F are the Eukaryotes. They can immediately see that the Phylogeny, the family tree, also results in a Classification. We’ve got 3 domains. And tell me about the relatedness. Yes – Archaea are more closely related to us than they are to Bacteria, even though they appear far more simple, even though they are also Prokaryotic, because they share a more recent common ancestor.

I know it’s gone well. The students are interested, involved, curious and asking really good questions. Hurrah!

But I didn’t get the job.

Which is fine. Sort of. Except that I was responding to an advert for a TEACHING post. So I was offering my services as a TEACHER, because I would, ideally, like to move away from the box ticking admin that increasingly occupies my time as a HoD, and back to what I like, what I’m good at. But whatever it was they were looking for, I didn’t fit it. Which puzzles me. There’s lots of things I’m rubbish at: dancing, singing, tennis, DIY, admin., remembering birthdays, growing hair…. but I know I can teach. Am I really not an attractive prospect as a teacher?

Sigh.

Oh well, it was a fun day out. And if nothing else, I have a super new lesson to add to my arsenal.

 

 

Handing out cigarettes…

My PGCE year had been great fun, but now it was nearly over and I was the only one on the course who didn’t have a job.

I had been hoping for a post somewhere in the South West so I could spend my weekends surfing. I wasn’t very ambitious. And I didn’t have too many criteria. The only things I was absolutely sure about were that it mustn’t be single sex, and it mustn’t be in London.

But suddenly it was June and the only advert in the TES was for St Paul’s Boys’ School, Hammersmith. I had never heard of the place, but a little research quickly confirmed it was way out of my league, somewhere my complete lack of a relevant Biology degree would be quickly exposed and I would be torn to shreds by packs of contemptuous 15 year old geniuses.

But my PGCE supervisor gently encouraged me, and so I sent off the application and, to my general astonishment, they called me for interview.

Running round frantically trying to locate a suit and tie, I was actually far more worried about the lesson I needed to plan. I had been asked to teach a class of Year 9s, which was fine, but my heart sank when I saw the topic: plant defences. The lesson was only going to be 35 minutes, but I have never spent longer formulating a lesson plan.

The first idea was to play safe: chalk and talk, a few examples, a few pictures, deliver the information clearly and effectively. Job done.

But the thought kept nagging me that this was deathly dull. Wouldn’t they want to see something a little more adventurous? Shouldn’t I be… myself? But  then again…. the topic… plant defences!?!?!?? What could I do?

I can’t remember when inspiration struck, but at some point, looking at the various examples, I came up with the idea of a party game, the kind where you have to find someone else with a matching role. How would this work? Maybe animals would have to find plants? And plants would… ah, yes, that’s it…. plants would have to find an appropriate defence. With 24 boys in the class, I could have 8 different sets of three, plants predated by specific herbivores and requiring specific defences.

I was very pleased with this, and set about designing and drawing the cards that each student would have. I’ve since lost the resource, and I can’t remember most of them, but there was a caterpillar and a leaf and nasty taste, and a gerenuk and an acacia and a thorn, and so on. There was also an elephant, a maize crop, and a chilli pepper grenade…

But I kept wimping out. A serious academic school like that would surely frown on such frivolity. The boys would laugh and dismiss me out of hand. It surely wasn’t “cool” enough. I kept returning to Plan A. Play safe.

And then kept circling back to Plan B – make it fun! And memorable! And different!

Two things swung me to the final decision. On the night before the interview, I suddenly realised that I had to be true to myself, they had to see the kind of teacher I aspired to be, even if the lesson was a crashing disaster, it would not fail for lack of ambition. But I had also had another thought, an idea for the opening, because I wanted a memorable start, a way to “hook” the students at the start….

… which is why, in my career defining interview lesson, I started the lesson by opening a pack of cigarettes and handing them round to the boys.

I can still remember the slightly stunned silence into which I dropped some cheerfully relaxed questions. So, what’s this stuff? Go on, pull it apart. What’s all this stuff inside? The stuff that people smoke? Yes, right, tobacco. Which comes from where? Yes, it’s a leaf. Do you know how big a tobacco leaf is? I sketch one on the board. They’re impressed. I start to relax – maybe this is going to work. What sort of things are in tobacco? They’ve all heard of nicotine. Any idea why a tobacco plant goes to the trouble of making nicotine? No? Well, it’s highly toxic, a thimbleful of pure nicotine will kill an elephant.

No question they’re interested now. They engage. They answer the question – yes, that’s right, the nicotine deters other organisms from eating the leaf. It’s protection.

We move on to the game. I deal out the cards at random – they have a silly little cartoon of the organism/protection, along with a few details of distribution and biology to help them find the right match. The gerenuk lives in Africa, so it needs to find an African plant. It browses on tree leaves, so it needs to find something suitably tree-like and leafish. Meanwhile the Acacia tree that matches the description, needs some spiky physical deterrent to fend off the gerenuk’s predations. Somewhere out there are some spines!

This lasts maybe 10 minutes and seems to go well. I get the “plants” to present back – what are they, what were they threatened by, how did they defend themselves? They learn from each other about the various spikes and stings and toxins and thorns and so on.

And so to the wrap up. The last “plant” to present is a maize plant. It’s grown by African villagers for their staple diet. And it’s predated by elephants who can trash a year’s supply of food in a night. In Uganda, they’re trialling the use of chilli pepper grenades to fend off the elephants without killing them. Appropriate technology, if ever there was some. But I think this is really neat. Why doesn’t the maize plant have it’s own defences? Because we’ve selectively bred them not to. And now we have to exploit the formidable defences of another plant, the chilli pepper and it’s potent chemicals, to protect our pampered, pathetic, selectively bred food plants.

The bell goes. Blimey, that was fast. Thank you very much. Er, can I have the cigarettes back?

Next day comes the letter. I’ve got the job.

Nude Carp Challenge

This term, I’ve been trialling a new lunch time club – Year 11 Genetics. The idea is to attract the very bright Year 11s who are fascinated by the topic, but who quickly get frustrated with how simplistic and uninteresting the iGCSE examples are. These, after all, include the girls who, last year in Year 10, bred ebony vestigial fruit flies and worked out dihybrid cross ratios from first principle. After that, tall vs short pea plants doesn’t quite cut it!

Except that this is where I started, pushing them to challenge the idea of “gene” for height. Really? How does that work, then? Genes code for proteins. What’s a “tall” protein? How can a gene code for “Tallness”?

So we take it back to basics. Tall plants have grown more than short ones. So what is growth all about? Cell division. So how could a gene possibly be associated with that? A hormone that stimulates cell division, perhaps. Ah! Good thinking. There is a hormone, or plant equivalent, with the wonderful name of Gibberellin. It stimulates stem elongation (pause for brief discussion of “foolish seedlings”). Except that Gibberellin isn’t a protein. There is no gene for Gibberellin….

They barely blink. Well, maybe there’s an enzyme that helps make Gibberellin. Enzymes are proteins. Could there be a gene for that?

Now we’re getting somewhere. But how could there be a “recessive” version of this gene? What’s going on there? A few prompts and they get it: do “recessive” genes simply not work? Are they mutations that don’t code for a working protein? So heterozygous plants grow tall because they have a working gene which can code for a working enzyme which will produce gibberellin and stimulate lots of cell division and “tallness”.

So to understand genetics,  you need to understand what DNA actually does.

They really like this because it has explanatory power. They’re not just matching up letters and traits in some trivial logic problem – they’re understanding the biochemical mechanisms. The following week, there’s more of them.

So this time I get them to review their dihybrid work from last year. And then throw linkage at them. It takes them some time, and there’s lots of brilliantly creative ideas along the way, but they get there. Perhaps these genes are on the same chromosome. So you inherit them together.

So to understand genetics, you also need to know the physical location of genes.

Week 3 and, oh look, the predicted linkage ratios don’t seem to be working out exactly. Where have that small percentage of apparently non-linked individuals come from? And why does that percentage seem to vary, depending on the trait? Crossing over and Morgan’s work on mapping chromosomes gets an airing.

So genetics is even more complicated and extraordinary than you realised!

Week 4 and we’re back to what genes code for. A 9:7 ratio of coloured sweet peas to white sweet peas. Huh? They figure out the principles of metabolic pathways and complementary epistasis.It’s just a pleasure and a privilege to watch them working together, trying out ideas, exlaining things to each other, that glorious lightbulb moment when they “get it”.

I add some points of my own. They like my analogy of a cake. You need ingredients, a mixer and an oven. If both the mixer and the oven work, you can turn the ingredients into batter, and then turn the batter into a cake. But if the oven is broken, all you get is batter. And if the mixer is broken, you can’t even get to the batter – you’re just stuck with the ingredients.

And that brings them nicely to the boil for the Nude Carp Challenge. Here it is:

Nude Carp Challenge

Go on, have a go. You will feel ridiculously pleased with yourself when you figure it out. Will my Year 11s? I’ll find out tomorrow!