Mini Dna 12 Layer Model. Comprising abstract shaped colour coded parts to represent the nitrogenous bases, pentagonal sugar and pyramidal phosphate parts required to make the Double Helix model of DNA. The model can be displayed on its stand or untwisted into either flat or ladder form. The kits are designed so that only complimentary bases can be joined together. Scale 10mm 2 Angstroms. choice of kits are available, either as an 12 layer or 22 layer. Each kit comes with stand and full instructions.