Deoxyribonucleic acid, better known as DNA, is located in the nucleus of all living cells. DNA dictates which creatures walk, fly, or bore through the soil. Each DNA strand is made up of four nucleotides or "building blocks": adenine, cytosine, guanine, and thymine. These nucleotides, in turn, are made up of a variety of proteins, called amino acids. The strands of DNA, made up of bonded nucleotide pairs, are very long. Molecular biologists have worked toward breaking the genetic code by identifying the nucleotides in order and searching for patterns.

Nature gave scientists one big hint: adenine always bonds with thymine, and guanine always bonds with cytosine. In the past, researchers found fluorescent molecules that mimic the natural nucleotides. When the known fluorescent molecule bonded with an unknown nucleotide, scientists could identify that particular bonded pair of the DNA strand. The process took a decade or...