Sequencing refers to the techniques that determine the order of the constituents of deoxyribonucleic acid (DNA) or protein. DNA sequencing determines the order of the constituent bases--adenine, thymine, guanine and cytosine. Protein sequencing determines the order of the constituent amino acids. DNA is typically sequenced for several reasons: to determine the sequence of the protein encoded by the DNA, the location of sites at which restriction enzymes can cut the DNA, the location of DNA sequence elements that regulate the production of messenger RNA, or to detect alterations in the DNA that might be important in genetic diseases, such as cystic fibrosis or cancer.

In recent years, the best known example of sequencing has been the effort to sequence the human genome, the complete set of genetic instructions carried within each cell of an organism. Decoding the DNA sequence of the human genome should pave the way towards...