The concept of the polymerase chain reaction PCR occurred to Kary Mullis one night while cruising on Route 128 from San Francisco to Mendocino. He immediately realized that this approach would be unique in its ability to amplify, at an exponential rate, a specific nucleotide sequence present in a vanishingly small quantity amidst a much larger background of total nucleic acid. Once its feasibility was demonstrated, PCR was quickly recognized as a major technical advance in molecular biology. The new technique earned Mullis the 1993 Nobel Prize in Chemistry, and today it is the basis of a large number of experimental and diagnostic procedures. At this keyword site you can learn more about the development of PCR from Mullis's original conception, including two major innovations that were necessary to perfect the process.

Many people think that birth defects are rare and happen only to other people. But about 4–5 percent of all newborns have some type of birth defect, amounting to 150,000 cases each year in the United States alone, and birth defects are the leading cause of infant death and disability. Some 3,000–5,000 different birth defects have been described. The most common are listed at this keyword site. The list includes only those conditions that can be diagnosed immediately at birth, and does not include such conditions as cystic fibrosis, Tay-Sachs disease, or sickle-cell anemia, which only become apparent in the first weeks or months after birth. Note that defects of the heart and circulatory system affect more infants than any other type of birth defect.

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