DNA manipulation. Computer artwork showing a segment of the molecule Deoxyribonucleic Acid (DNA) in the process of being cut with a scalpel. A part of the molecule has been located which may be the site of an important gene. DNA contains the inherited instructions necessary for the develop- ment of a living organism. It consists of two strands twisted into a helical shape, with bases (bars) projecting inwards. These bases of four types pair up in a complementary fashion to form a code of genetic instructions. DNA manipulation (genetic engineering) might involve cutting the molecule up and resplicing it to other fragments. Genetic diseases may be treated in this way.