Thank Wired Up it’s Friday!

This week we are looking at sneaky science.  Fingerprinting, forensics and fiendishly-identifiable fluids.  So whodunnit? Who stitched up Pluto? It seems that its planet-ishness has been called into question. How very dare you!  Read on and see what you think.

1. The Wire – How round is your planet?
2. You What?  – SmartWater, the latest security device
3. Planet Picks – how to become a forensic scientist
4. Try This! – Sticky fingers
5. Gear for Grabs – Fingerprint Detective Tube

Have you heard of SmartWater?  No it’s not some fancy new sports drink, it’s a security method. It acts a bit like a security marker.  You know when you write your postcode on your belongings and it can only be read under ultraviolet light?

SmartWater is a liquid containing uniquely numbered micro-dot particles. The smallest amount is sufficient for identification under a microscope. There are millions of combinations, each uniquely coded and licensed to an individual. A bit like DNA. Codes are held on a secure database.

Its unique forensic fingerprint is almost invisible to the naked eye. It fluoresces under ultraviolet light, and is virtually impossible to completely remove. Particles will remain on clothing indefinitely and can stay on the skin for weeks.  Criminals coming into contact with SmartWater can instantly be connected to the crime. Amazing eh?  Forensic science just gets better and better.

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Fingerprints – whodunnit?

You will need:

• Fingers + friends' fingers
• An assortment of drinking glasses - make sure they're clean!
• Cocoa powder
• A small artists' brush
• A magnifying glass
• An inkpad
• White paper - one sheet per person

What to do:

1. Give everybody a glass and a sheet of paper.
2. Get each person to make a finger or thumb mark on the rim of the glass.
3. Once they've done this, the detective work starts. Swap glasses, being careful to touch only the base of the glass. Don't smudge the prints that are already there!
4. Examine each glass for fingerprints. Using the brush, place a small amount of cocoa over where the prints were made.
5. Use the brush to lightly dust over the prints to help make them a bit clearer.
6. On sheets of paper, get each person who left a print originally to make another print - but this time they have to press their finger or thumb in the inkpad first.
7. Match these new prints to the ones you duster for earlier. Use the magnifying glass to help you inspect them even more closely and try to match them up.
8. See if you can name the 'culprit' who left their prints on each glass. When you've had enough, wash and dry the glasses, and start again!

What’s happening:

No two fingerprints are the same; even twins will have differences in their prints.

When you examine a print you'll notice the lines occur in one of three characteristic patterns, known in the biz as 'arches', 'loops' and 'whorls'.

When you come to compare the chocolate and the ink prints you should get an exact match between pairs. But although two different people may have the same fingerprint type (e.g. both have loops on the same finger), there will always be other little differences between individuals. That's because it's not the shape of the print that's unique, but rather the number, location and shape of specific ridge characteristics...

What you were lifting with the cocoa powder are called 'latent' prints. These prints are formed by oil and sweat from a person's fingers when they touch a surface - the sweatier you are the clearer they'll be! They're invisible to the naked eye, which is why they need the dusting to help you see them...

Another method of taking your prints is to scribble on a piece of paper with a pencil then rub your finger over the scribble.  You should now have a nice grey fingertip! Now carefully take a piece of sticky tape and press the sticky side over your fingertip.  As you slowly peel it off you will see a very clear fingerprint stuck to it.  Stick this fingerprint down onto a white piece of paper. The features are very obvious, aren’t they?

If this has made you want to try more then look at the Creative Chemistry site.

There’s also a printable worksheet suitable for younger scientists in Dynamo's Lab on the BBC Education website.

Happy printing!

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Build a colourful and tasty model of a DNA strand - a perfect excuse to go and buy lots of yummy sweets from a pick and mix shop! (and eat them!)

You will need:

• 2 different coloured long candy or liquorice cords with a fondant centre
• 1 large packet of midget gems or similar sized soft sweets
• 1 box of cocktails sticks
• Needle and thread

What to do:

1. Take the two candy cords - assign one colour to represent the pentose sugar molecules and the other to represent the phosphate molecules.
2. Cut the candy cords into 2 - 3 centimetre pieces.
3. Using the needle and thread string half the candy pieces together lengthwise alternating the two colours to form a chain.
4. Repeat step 3 with the remaining half of candy pieces to form a second chain of the same length.
5. Lay the two chains down side by side so pieces of the same colour are opposite one another.
6. Count the number of pentose sugar molecules you have in one chain (you should have the same number in both chains). Then take this number of cocktail sticks. These represent hydrogen bonds that hold the base pairs together.
7. Divide the packet of midget gems and into four different colours. Assign names to the each of the four colours to represent the nucleotide bases - adenine, cytosine, guanine or thymine.
8. The bases have to be paired up on the cocktail sticks. Adenine always pairs with thymine and guanine with cytosine, so make sure you get the right colours matching.
9. Push each end of a cocktail stick into candy pieces representing pentose sugar molecules lying opposite one another - the cocktail sticks should join the two chains together so they look a bit like the rungs of a ladder.
10. Hold the end of each chain and twist slightly to get the double helix effect for your DNA model.

What’s happening?

The structure of DNA is known as a double helix and was determined in 1953 by Crick and Watson.  DNA stands for Deoxyribonucleic acid and is a code containing all our genetic information.  We could call it the recipe for life. The Human Genome Project (HGP) sequenced and mapped all of the genes - together known as the genome - of members of our species, Homo sapiens. Completed in April 2003, the HGP gives us the complete genetic blueprint for building a human being.

For more information on the Human Genome Project (HGP)

Find out more DNA facts and trivia.  Maybe even do the DNA dance.  Come on sugar! Swing yer bases!