DNA nanotechnology
Figure 5. (a) The self-assembly properties of the DNA double helix can be exploited to make a variety of structures. In this case (left), the bases on one molecule (red) bind together with the fragments of two other molecules (green and blue) that have complementary bases. When a fourth fragment is added (black), the result is a cross. Seeman's group at New York has built three-dimensional structures, such as cubes (right), using this principle.
(b) DNA chips are patterned with many short snippets of single-strand DNA, each with a different sequence of bases. When DNA has been extracted from a cell, for example, and labelled with a fluorescent marker, it will only bind to the fragments that have exactly the right genetic code. Currently the chips are read out optically by searching for the fluorescent markers, but the electronic properties of DNA might soon be exploited for this purpose. (Picture credit: N Seeman/New York University)