Kary Mullis

Biotechnology owes a lot to Kary Mullis (1944 - ). During a long evening drive in 1983, he invented a way to turn a single piece of DNA into millions of identical copies– and it’s as easy as tossing ingredients into a test tube. Mullis was born in the foothills of rural North Carolina, a childhood still vivid to him. He credits his undergraduate training in physics, chemistry and math at Georgia Tech with teaching him "most of the useful technical things" that he has used in his scientific work. The rest he learned during his PhD work in biochemistry at the University of California, Berkeley and postdoctoral training at the University of Kansas Medical School. Eventually Mullis returned to California and found himself making oligonucleotides, short single-stranded sequences of DNA, with Cetus Corporation.

One spring night, while driving to his cabin with a friend, Mullis started thinking about DNA. He knew that, in nature, cells copy DNA by separating the two strands and duplicating them with a DNA polymerase. Mullis realized that he could instruct the polymerase to copy a specific gene – he just needed to add a couple of primers, oligonucleotides that would stick specifically to that gene. During that long drive, Mullis thought out his technique. He would add the right primers to a piece of DNA, heat it to separate the strands, cool it to let the primers attach, then let a polymerase duplicate each strand. Instead of a single piece of DNA, he would have two. If he raised the temperature again, the newly made DNA would split apart and be ready for another round of replication. Each time the cycle was repeated, the amount of DNA would double. The genius of this method, the polymerase chain reaction (PCR), is its simplicity. With a few ingredients and some temperature changes, a single piece of DNA can be turned into over a billion copies in a few hours.

Mullis and a colleague at Cetus, Fred A. Faloona, soon worked out the technical details that turned Mullis’ idea into reality. At first, researchers used ordinary polymerases, which are destroyed by heat and must be added fresh at each cycle. But with the discovery of Taq polymerase, a heat-stable version from a hot springs bacterium, the procedure became even simpler. Its ingredients now need only be added to a test tube and the temperature cycled up and down. PCR has revolutionized genetics and medicine. With it, physicians can identify viruses and bacteria in human tissue samples without time-consuming culture techniques. They can find genetic defects in a fetus in a matter of hours instead of weeks. Forensic scientists can look for DNA in a drop of blood or a single hair. And, as aficionados of science fiction know, PCR can even isolate DNA from extinct animals. In 1993, for his amazing discovery, Mullis shared the Nobel Prize in Chemistry.

 Sources

Gibbs, Richard A.. 2000. Polymerase chain reaction. MicrosoftÒ EncartaÒ Online Encyclopedia 2000. Available at: http://encarta.msn.com/find/Concise.asp?ti=0AC84000 Accessed September 22, 2000.

Microsoft Corporation. 2000. Mullis, Kary B. MicrosoftÒ EncartaÒ Online Encyclopedia 2000. Available at: http://encarta.msn.com/find/Concise.asp?z=1&pg=2&ti=761582668 Accessed September 22, 2000.

The Nobel Foundation. 2000. Kary B. Mullis. Available at: http://nobel.sdsc.edu/chemistry/laureates/1993/mullis-autobio.html Accessed September 22, 2000.

[The source of the Mullis quote]

The Nobel Foundation. 2000. Press Release: The 1993 Nobel Prize in Chemistry. Available at: http://nobel.sdsc.edu/chemistry/laureates/1993/press.html Accessed September 22, 2000.