||Make several copies of the nucleotide templates on card. Ten nucleotide pairs are required for a complete turn of the double helix. To see the major and minor grooves in the double helix clearly, the model needs to have at least 16 nucleotide pairs.
||If desired, colour in the pieces appropriately. The colours that are often used in sequencing markers for DNA bases are: Cytosine=Blue; Guanine=Yellow; Adenine=Green; Thymine=Red.
||Cut out the nucleotide pairs around the thicker, outer lines. Make two small cuts into the card by the phosphate groups where indicated. OPTIONAL: Use a sharp craft knife to make cuts above the deoxyribose molecules where shown.
||Carefully punch a small hole in each cut-out where shown. This will be the axis of the DNA model through which the string will be threaded. Do not make these holes too big!
||Fold the sugar-phosphate ‘backbones’ where indicated by dotted lines. These folds must be made in the directions shown on the diagram in the PDF file. Take care not to make left-handed DNA!
||Cut 25 mm lengths of drinking straw. You will need one less piece of straw than you have nucleotide pairs.
||Glue the phosphate group on one cut-out onto the deoxyribose on the next. Do the same with the opposite sugar-phosphate strand. Remember that the sugar-phosphate chains run in opposite (anti-parallel) directions. The orientation of the letters on the card should help you to assemble the model correctly.
||Hold a piece of drinking straw between the holes in the cut-outs, and thread the string through them.
||Repeat steps 5-8 for as many nucleotide pairs as desired.
||Cut out the genetic code, and glue the two sides together onto the string at the bottom of the model. This will help the model to hand vertically.