Sunday, 20 March 2011

When Watson and Crick met Haribo

Every March, Cambridge hosts a Science Festival - two weeks of events, all free, covering everything from maths to astronomy, physics to veterinary science. Departments open their doors and invite the public in, and if you miss it, you really do miss out.

Most of the events happen on the first Saturday, and that happened to be yesterday. There's far more on offer than we can possibly manage, so we are selective about the events we attend. This year - oh joy! - we managed to fit in a lot of cell biology, my very favourite subject. So, this week, in honour of the festival, I'm going to attempt to bring back Kiddie Science. Hurrah! For background on DNA structure, in case this makes no sense at all, this is a very good place to start.

One of the groups we visited came from the institute where I used to work, and they had a fun and simple table introducing the idea of DNA structure using gummy bears. We decided to take it one stage further. If you want to have a go too, you will need a packet of cocktail sticks and a LOT of jelly sweeties.


Simply put, the most common form of DNA is a bit like a ladder that is twisted around to form a double helix. In order to model a small part of it, first we built a pair of phosphate backbones - like the outside edges of the ladder - using two colours of jelly babies and some cocktail sticks. Observant biologists will notice that the two strands are running in opposite directions with the heads of the red men pointing away from the heads of the yellow men.


The part of DNA that does the clever genetic coding are the 4 nucleotides, or bases, that fit between the long backbones like the rungs of the ladder.

These bases are of two types - the larger purines adenine and guanine (A and G), and the smaller pyrimidines thymine and cytosine (T and C). One of the crucial things to realise is that there is only a limited amount of space in between the backbones, so in order to keep your ladder legs parallel, you need to pair a large (purine) base with a small (pyrimidine) one - in this case our two choices for the large bases were red and yellow fruity bobbles, while the small bases were purple and orange gummy bears. The girls soon decided which sweets to pair together and our first molecule was made.


Now, as Watson and Crick very soon realised, this complementary base pairing gives a huge clue as to how DNA can be accurately replicated - essential if you're a cell that wants to divide properly! So, we split the two halves of the molecule apart:


and used each half as a template to build a second strand.


Now all we had to do was skewer our rungs with cocktail sticks,


Pick up the ladders and give them a twist:


to form a giant edible DNA double helix!


Apologies to 1. cell biologists; and 2. vegetarians. My DPhil supervisor would be so proud!

28 comments:

  1. What a cool way to teach kids about science. You lost me with all of the ides, but I'm guessing that candy would definitely keep my attention. Oh -- and I'm not sure why the apology to vegetarians? I'm thinking I missed something!

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  2. Fantastic! DD1 will be getting a chemistry set and microscope for her birthday later this week, but I think that haribo and cocktail sticks might just have to appear on the present list too! Thanks for this!

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  3. what a fantastic way to make science fun!

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  4. Another great post ons science, you always make it so much fun!

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  5. Very clever Mrs Cookie! Although I think you lost me on the jelly babies!

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  6. You had me at phosphate backbone.

    Thanks for the nostalgia, Mrs.

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  7. Hoorah for kiddie science! (You might need to explain it to me again though, very slowly)

    I can imagine you and Silverpebble talking about this stuff forever. I can imagine us all meeting up and me just sitting in a corner clueless drinking and saying nothing and you having to take me to the hospital.

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  8. Fabulous! I love all this kind of science stuff, although I'm not sure the haribos would have lasted long enough to be made into DNA in this household!!
    R x

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  9. I'll read this again when I've thrown off this virus!

    But it's really cool - I wish my school science lessons had been like that.

    You're brill!
    Celia
    x

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  10. Hooray for Dottycookie double helix. Hooray for haribo. And a bit of credit has to go to Watson and Crick. We have missed the best of science week this year, must remember to keep it free next year. Hope all's good with you, Ax

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  11. Oh Val this is brilliant! I so love your science posts which always manage to make a dauntingly complex subject accessible and fun!

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  12. You had me at the title!

    I shall be sharing this with Pr. C-W and d/Boy over the Easter holidays as that will allow plenty of time to a) create the dbl helixes(ices?) and b) accumulate the amount of jelly bobs req'd to construct said helixes(ices).

    Anna, the gelatine in jelly bobs is made from a very vegetarian-unfriendly product.

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  13. Such fun! Can't imagine my son in particular ever completing this as he is completely unable to resist haribo (or any other sugary treat for that matter) temptation! Oh and I gave myself a pat on the back for remembering who Watson and Crick were despite it being over 20 years ago since A level biology....!

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  14. Please stop posting in Hungarian.

    Love from Too Stupid To Understand Science.

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  15. oohh my eldest would have loved that! I really must try and go to some of the science things next year.

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  16. so cool--what a fab idea and so much fun! wish we could have gone to the science fair, we are big fans of those.

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  17. You are the coolest person ever. The.Coolest.

    And surely I could find some non-gelatinous gummy bears somewhere. I'll check at the natural foods grocery...

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  18. I wish we'd done science with sweets at school, still don't really understand it but it looks so much more interesting!
    Sounds like a great event for encouraging scientists of the future.

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  19. Fantastic!!!

    I'm going to do this will my kiddos. I'm sure my budding little scientist will love it :-)

    Thanks very much.

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  20. You're brilliant! Cocktail sticks and jelly sweets - what's not to love!? Science is fun and tasty too!

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  21. ok... my head hurts.

    I could get me kids to do anything if sweets are involved so I might have to give this a try!

    (And I'll show this post to Mr M who thinks blogging is all fluffy and silly... ha.)

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  22. If science had been like that they'd have kept me past GCSE....

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  23. I love this, and I'm off to buy some jelly sweets! Then it's quantum physics time, when atoms can spontaneously jump from one place to another (with the little known fact that the destination is usually someone's mouth).

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  24. wish you'd been my science teacher - i might have gone on to A level!!!

    xxx

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  25. Wow, that was really fun to make, creativity is really shown. Now I ask my self why haven't I thought of that, cocktail sticks and jelly sweets- instant DNA gummy treats.

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  26. You are just too clever for words! What a wonderful way to demonstrate! Hope you all enjoyed eating the props! Lucy xx

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