Double Trouble – Building a Double Helix Teacher Notes The purpose of this exercise is to reinforce the elements learned in module 2 of the programme in a fun hands-on way. Use the information on genes and DNA from the programme support pack to revise this subject while children are making the double helix. DNA is like a chemical language which writes the instruction manual for our bodies. There are 2 single DNA strands wrapped around each other like a spiral stairs in a shape called the double helix. DNA is made of just 4 chemicals: A – adenine T – thymine C – cytosine G – guanine Along this double helix, A always joins with T and C always joins with G. In this lesson, children will make a DNA double helix model using craft material which can be taken home or displayed in the classroom. What you will need Coloured paper or card, toothpicks, 4 coloured markers, a pencil, sellotape, glue. Teacher preparation It may be helpful to have the paper strips pre-cut. Skills Development Questioning, Estimating & Measuring, Recognising Patterns. Activities 1. To make the sides of the DNA ladder, cut two strips of coloured paper that are at least 2ft long and 2in wide. If you don’t have paper that is 2ft long, cut several strips and stick them together to make this length. 2. To make the rungs of the ladder choose 4 different coloured markers and decide which colour will represent each chemical base e.g. red = A, blue = T, yellow = C, green = G. 3. Count out 10 toothpicks and colour half of each one in red and the other half in blue (remember A is always paired with T). 4. Count out another 10 toothpicks and colour half of each one in yellow and the other half in green (remember C is always paired with G). 5. To construct the double helix, lay each side of the DNA ladder on top of each other and tape them at both ends. 6. Draw little dots with a pencil along the centre of the DNA ladder at ½ inch intervals. There should be 20 in total if you make a ladder of around 2 ft. Leave a little space at the top and bottom of the ladder. 7. Poke the toothpicks through these dots in any order you like. Push them through so that half of each toothpick is visible on each side of the paper ladder. 8. Once all the toothpicks are in place, gently spread the two paper sides of the ladder apart until the model looks like a ladder. If any toothpicks fall out at this stage, simply apply a little glue to keep them in place. 9. To create the spiral twist, tape the top of the model to the wall on which you would like to display it and gently twist it at least once until it looks like a double spiral. Tape the bottom to the wall too to keep it in place. Safety • Care should be used when handling the toothpicks and applying the glue. • Children who use glue should wash their hands immediately after the exercise.
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