πώς η ρύπανση του υπόγειου υδροφόρου ορίζοντα φτάνει στο ποτήρι μας;

η ρύπανση καταλήγει στην βρύση μας

αυτό το πείραμα το έχουν κάνει μερικά παιδιά στο 5ο Λύκειο Πετρούπολης αλλά νομίζω πως είναι εφικτό και για πιο μικρά παιδιά.

για τις διακοπές ...

Ουφ! Διακοπές! Επιτέλους,έφτασε η ώρα να κλείσουμε τα βιβλία και να κάνουμε κάτι πιο ...ενδιαφέρον.


Τι θα λέγατε για ένα "πείραμα" λίγο αλλιώτικο...λίγο πιο βιολογικό?

Ιδού λοιπόν...η ιδέα: πώς να φτιάξουμε την έλικα του DNA με απλά γλυκά...

Καλή Επιτυχία και Καλή Ανάσταση!

======================================


So here's how to make jelly baby and liquorice DNA.
 
Photograph: Mark Lorch 
 
You'll need:
Two long, flexible sweets, such as liquorice ribbons.
A few handfuls of soft, highly coloured sweets, such as jelly babies or marshmallows.
Cocktail sticks.

 
  Photograph: Mark Lorch 
 
1) Sort the sweets into colours. Keep four of the groups, eat the rest.
2) Pair up the sweets so that one particular colour always goes with another particular colour e.g. red with green and yellow with purple.

 
Photograph: Mark Lorch 
 
3) Stick the pairs onto cocktail sticks as if you were making candy kebabs.

 
Photograph: Mark Lorch 
 
4) Attach your candy kebabs to the long sweets. Carry on doing this until you have something that looks a bit like a ladder.

 
Photograph: Mark Lorch 
 
5) Pick up your ladder and give it a twist.

 
Photograph: Mark Lorch 
 
Hey presto, a model of DNA made from sweets!

The paired coloured sweets represent the base pairs that contain all the genetic information, while the liquorice is the sugar/phosphate backbone of DNA.

και τώρα...εκχύλιση του DNA από ένα ακτινίδιο!

Extracting DNA from kiwi fruit

You'll need:
A peeled kiwi fruit
A blender
Surgical spirit (or vodka)
Washing-up liquid
Table salt
A strainer
A glass tumbler

 
Photograph: Mark Lorch 
 
1) Chill the surgical spirit by leaving it in the freezer overnight.
2) Blend or mash the kiwi.
3) Add one teaspoon of salt and one teaspoon of washing-up liquid to 100ml of hot water (from the tap should be fine). Gently stir, then add to the blended kiwi.

 

Extracting DNA from kiwi fruit. Photograph: Mark Lorch
4) Leave it to stand for about 15 minutes.
5) Pour the kiwi mixture through the sieve to remove the pulp and seeds.
6) Gently add about 20ml of the cold surgical spirit.

 
  Photograph: Mark Lorch 
 
The surgical spirit should sit on top of the kiwi mixture, and in this top layer some white cloudy stuff will form. That white stuff is DNA.
The blending, salt and washing-up liquid break up the plant cells, releasing the DNA. It dissolves in water but not in surgical spirit (which is basically alcohol), so when you pour it onto the mixture the DNA precipitates out of solution.

[από How to make a DNA double helix from jelly babies and liquorice]


Mark Lorch is a chemist at the University of Hull. He blogs at 'Try This At Home and tweets as @sci_ents