Title: Make a scrap card DNA model

 BIGGEST EVER MATHS & SCIENCE LESSON GUINNESS WORLD RECORD DAY NOVEMBER 2015 Title: Make a scrap card DNA model Resources: Cereal packet or similar scrap card, colouring pens in 4 colours, scissors, ruler, pencil, glue. Method: • Draw two parallel lines 25 centimetres long and 5 centimetres apart. •
Make marks along each edge at one centimetre intervals. •
Draw lines joining the points marked on one edge to points 5 centimetres along the opposite edge so that the lines are at an angle of 45o to the edges. •
Draw parallel lines one centimetre in from each side. •
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Cut out your strip Fold the ladder in two lengthwise You are going to cut out alternate sections to make a ladder. • While the ladder is folded in two lengthwise, make very small cuts on the centre of the spaces between the steps so that you will be able to make a start in cutting spaces between the steps of the ladder • Flatten the ladder. • Cut out alternate sections making a ladder with steps one centimetre wide and one centimetre apart. If the card is blank on both sides the following step is not necessary. •
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If the card you use is not blank on both sides repeat the above to make a second ladder like the first one. •
Glue the two ‘ladders’ back to back so that you can colour the steps of the ladder both back and front. •
To represent the pairs of bases, colour each step of the ladder either half yellow (for Guanine) and half blue (for Cytosine) or, on other steps, half red (for Adenine) and half green (for Thymine). Colour both back and front of each step the same. •
Choosing the base pairs in random order, colour all the steps. If you make projecting feet to each ladder as shown you can glue the ladders together into long chains. •
Twist your ladder. •
If you have made ten steps then twist it to show one complete revolution as in the diagram. In the DNA double helix each step of the ladder corresponds to a twist of 36o. This model is a rough approximation to the general shape of the DNA double helix but does not allow for the complex geometry of the molecules and the bonds between them. Follow-­‐up suggestions • Mark S for Sugar and P for Phosphate alternately down the edges of the ladder to show how each base is attached to one sugar and one phosphate molecule which join together to form the edges of the DNA ladder. • As a class project the models made by different learners can be joined into a long chain either by gluing or stapling them together.