DNA molecule. Computer graphic of a view down a strand of beta DNA (deoxyribonucleic acid). Atoms are depicted as balls and sticks and are colour- coded: carbon (white), nitrogen (dark blue), hydr- ogen (light blue), oxygen (red) and phosphorous (orange). Beta DNA is the common form, and spirals clockwise when seen from above. The purple line follows the molecule's spiral shape. DNA contains the inherited instructions necessary to produce an organism. The DNA molecule is made up of two spiral strands of atoms joined by the interactions of cross-linking bases between them. The sequence of bases along the strands makes up the genetic code in the form of genes, segments of DNA.