Monday, July 9, 2012

Having fun with science at home

This tweet made me think a blog post on the subject would be fun.

A good place to start is the New Scientist's book How to Fossilise Your Hamster (which I won't link to on Amazon - please support your local bookshops!). You can get started with five videos that the New Scientist put together to promote the book. These will show you how to make plastic with milk; get ketchup out of the bottle; watch the interaction of cream and tia maria; make fizzy drinks fizzier and how to extract iron from your cereal.

Another good place to start is the ever excellent Richard Wiseman especially his videos ‪Top 10 quirky science tricks for parties‬; Ten more science stunts for parties; and Another 10 quirky science stunts. You can also take part in a real science experiment with his DreamON app.

There are obviously many experiments and practicals that you can do, but as biological sciences are my favorite, here's how you can extract your very own DNA:

You will need:

Half a tea spoon of salt
250 ml of warm water
Clear dish soap
Surgical or methylated spirits, chilled (or pure ethanol if you have it).
Syringe or dropper
Cups, shot glasses/test tubes.

How to do it:

Poor water in cup, add salt, and stir. Swirl the water around in your mouth for at least 30 seconds. It can help if you rub your cheek against your teeth before swirling the water - the aim is to get your own cheek cells into the water, as this is where your DNA source is coming from.

Spit this solution into a clean cup. Add 1 to 1 1/2 teaspoons of the solution to a test tube, or a shot glass.

In a separate cup, add three teaspoons of water to one teaspoon of clear dish soap. Stir it to mix it - but do not make it foam.

Add one teaspoon of this to the test tube. Stir this, but again, being careful not to make any bubbles.

Add one teaspoon of the chilled alcohol to the test tube. Do this carefully, it must float in a layer on top of the solution. DO NOT STIR. Leave it for two minutes.

Use syringe, or dropper, to carefully remove the top layer of alcohol, and transfer it to a shot glass of the spirits. You will see white bits floating in the alcohol - that's your DNA!

The science behind this:

The dish soap is there for two purposes. Your DNA is contained within membranes, and you need to get through this membranes to get to the DNA. The detergent in the dish soap does this. The dish soap will also (hopefully) contain enzymes - these will help break down the proteins that are associated with the DNA. Once the DNA has been released, it clumps together - because of the salt right at the beginning. These clumps of DNA dissolve just fine in water, but not so in alcohol. When they get into contact with the alcohol, they form a solid (what is called a precipitate). This floats to the top, and as DNA tends to be long and stringy, it pulls more DNA with it.

You can adapt this technique - it doesn't have to be your DNA. Blended peas or strawberries, for example, can give considerably more DNA, but I chose doing your own DNA, as it's quite fun to look at your own blueprint.

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