Monday, November 12, 2012

Shaken not stirred - how to extract your own DNA

Last week I eagerly sat down to watch the first episode of a new series: Dara O Briain's Science Club. For those of you from outside the British Isles, Dara O Briain is an Irish comedian who, in recent years, has become one of the most popular comedians and broadcasters in the UK. Not only is he a very funny guy, he's also got a pretty sharp mind inside his (frankly massive) shiny head: he studied mathematics and theoretical physics at University College Dublin and has managed to hang on to his love of science despite moving into the world of entertainment. He, along with other big names like Brian Cox and James May, has been instrumental in advancing British popular science broadcasting in the last decade and has presented a number of science programmes, such as School of Hard Sums and Stargazing Live, giving science that much-needed welcoming and friendly face. 

His new series is most definitely worth watching and I await the next episodes with bated breath. The first was on the subject of genetics and epigenetics and my curiosity was more about how these complex topics would be presented rather than actually learning something (I'm already fairly familiar with the fields)! I was delighted by the casual and approachable way in which it was structured, and how debates about scientific funding and application were mixed in with the hard facts. 

Possibly my favourite moment, however, was when we were shown how to perform a simple task that I am very used to doing in the lab, but in your own home: extracting DNA. Perhaps appropriately given the latest addition to the James Bond franchise, this entailed the use of cocktail-making equipment and the kind of very strong vodka needed to make that perfect Martini. Some might think of this as a big gimmicky and irrelevant, but I quite like the idea of making somewhat abstract scientific principles more tangible in the mind of the general public. Bringing such a standard research procedure into people's homes helps to demystify the scientific method and hopefully give people a greater sense of ownership over this work than they might otherwise have.

So, today's post is a shameless plug for Dara O Briain's Science Club with the aforementioned DNA recipe thrown in for those of you unfortunate enough not to be able to watch it online! Enjoy.

1. Collect some of your cheek cells by swishing some (around 100ml) salt water around your mouth for 30 seconds or so. The solution will be a bit cloudy afterwards.

2. Add a few drops of washing-up liquid (to dissolve the cells' membranes) and a shot of pineapple juice (the proteases in this will degrade the myriad proteins found in your cells). Pop it all into a cocktail shaker and give it your best shake!

3. Pour through a cocktail strainer to remove bubbles, ideally into a martini glass or something in which it's easy to layer different liquids.

4. Chill some very strong (>80% abv) vodka on ice and they carefully layer over the top of your mushed up cell solution. At such a high concentration of alcohol DNA comes out of solution and so precipitates at the boundary between the two solutions. This looks like a white cloud forming at the bottom of the vodka layer, which can be scooped out by wrapping it around a toothpick or something similar. Et voilà! It may not look like much, but you have successfully extracted the chemical instructions that make you you. Not bad for 5 minutes work.


  1. I can beat this (I can argue why I think this wins, if you want). How to make your own cosmic ray detector:

  2. I'm just now watching them measure the speed of light using some cheese in a microwave - they got 3.2x10^8m/s, not bad at all but my favourite bit was watching Dara O Briain taunt a cheese-phobic guy with the cheese they were using.

    The cosmic ray thing is pretty cool too, I might give it a go in the lab one day!

    1. I'm going to be a pedant here, I haven't seen the show (iplayer won't let me and nobody on youtube has uploaded it)... I imagine what they did was measure the wavelength of the microwaves, but how did they *measure* the frequency?.

      That's not to take away from the fact that it is pretty cool to measure the wavelength of microwaves with cheese.

    2. You're quite right, they measured the wavelength and used the frequency that the microwave was set to but didn't measure that directly.

      Can you think of a way to measure the frequency of a microwave oven with simple household objects? If so you could combine the two approaches!