Dr. Kary B. Mullis

American biochemist Dr. Kary B. Mullis (1944- ) won the 1993 Nobel Prize for chemistry for revolutionizing the fields of biology and medicine with his method for producing abundant fragments of deoxyribonucleic acid (DNA). His Polymerase Chain Reaction (PCR) enables scientists to create sequences of genetic material in quantities that are large enough to study. PCR has played a major role in the International Human Genome Project, which has major health and antiaging implications. The technique has also become invaluable in disease diagnosis, forensic-science analysis in convicting the guilty and freeing the falsely accused, and the study of DNA from ancient or fossil tissues. Mullis shared the Nobel Prize with British-born Canadian biochemist Michael Smith, who was honored for devising a technique to control the formation of proteins. In 1998 Mullis was inducted into the National Inventors Hall of Fame in the United States.

Born in Lenoir, North Carolina, Mullis received his Ph.D. degree from the University of California, Berkeley, in 1973. After postdoctoral work at the University of Kansas Medical School, he joined California's Cetus Corporation as a research scientist in 1979.

Mullis made his discovery while working at Cetus in 1983. Prior to his work, it was extremely difficult and time-consuming to obtain adequate fragments from a large mass of DNA. They also could not be produced artificially in the laboratory. His method was simple but effective. First, Mullis heated his DNA sample to get the two complementary strands of the double helix that make up the DNA to separate. As the sample cooled, he added two short DNA sequences, which bonded to the complementary sites on the separated strands. This marked the sequence of nucleotides (the four building blocks of DNA) that Mullis wanted to reproduce. He then added a number of free nucleotides and a polymerase enzyme (proteins that cause or accelerate a chemical reaction), which joined the nucleotides in the same order as the targeted segment. Thus, he had produced a copy of the desired DNA sequence. By continually repeating the process on the copy (doubling it with each procedure), Mullis was able to increase his product exponentially. It was now possible to produce billions of copies in just a few hours. This innovation was so crucial that when Cetus closed in 1991, Hoffman-La Roche purchased the PCR patent for $300 million.

In 1986 Mullis became director of molecular biology at Xytronyx Inc., a plastics manufacturer in San Diego, California. Since 1988 he has worked as an independent consultant for various firms.

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