American biochemist Kary Mullis designed polymerase chain reaction (PCR), a fast and effective technique for reproducing specific genes or DNA fragments that is able to create billions of copies in a few hours. Mullis invented the technique in 1983 while working for Cetus, a California biotechnology firm. After convincing his colleagues of the importance of his idea, they eventually joined him in creating a method to apply it. They developed a machine that automated the process, controlling the chain reaction by varying the temperature. Widely available because it is now relatively inexpensive, PCR has revolutionized not only the biotechnology industry, but also many other scientific fields and it has important applications in law enforcement, as well as history. Mullis shared the 1993 Nobel Prize in chemistry with Michael Smith of the University of British Columbia, who also developed a method for manipulating genetic material.
Kary Banks Mullis was born in Lenoir, North Carolina, on December 28, 1944. As a high school student, Mullis designed a rocket that carried a frog some 7,000 feet in the air before splitting open and allowing the live cargo to parachute safely back to earth. Mullis entered Georgia Institute of Technology in 1962 and studied chemistry. As an undergraduate, he created a laboratory for manufacturing poisons and explosives. He also invented an electronic device stimulated by brain waves that could control a light switch.
Upon graduation from Georgia Tech in 1966 with a B.S. degree in chemistry, Mullis entered the doctoral program in biochemistry at the University of California, Berkeley. In Berkeley, at that time, was growing interest in hallucinogenic drugs; Mullis taught a controversial neurochemistry class on the subject. At the age of twenty-four, he wrote a paper on the structure of the universe that was published by Nature magazine. He was awarded his Ph.D. in 1973 and he accepted a teaching position at the University of Kansas Medical School in Kansas City, where he stayed for four years. In 1977, he assumed a postdoctoral fellowship at the University of California, San Francisco. In 1979, he accepted a position as a research scientist with a growing biotech firm, Cetus Corporation, in Emeryville, California that was in the business of synthesizing chemicals used by other scientists in genetic cloning.
Reproducing deoxyribonucleic acid (DNA) had long been an obstacle to anyone working in molecular biology. The most effective way to reproduce DNA was by cloning. Although cloning technology represented a significant scientific advance, it was still a cumbersome process in certain respects. DNA strands are long and complicated, composed of many different chromosomes; the problem was that most genetic engineering projects were tasks that involved tiny fragments of the DNA molecule, almost infinitesimal sections of a single strand. Cloning works by inserting the DNA into bacteria and waiting while the reproducing bacteria create copies of the DNA. The cloning process is not only time-consuming, but it replicates the whole strand, increasing the complexity. The revolutionary advantage of PCR is its selectivity; it is a process that reproduces specific genes on the DNA strand millions or billions of times, effectively allowing scientists to amplify or enlarge parts of the DNA molecule for further study.
Scientists at Cetus developed a commercial version of PCR and a machine called the Thermal Cycler; with the addition of the chemical building blocks of DNA, called nucleotides, and a biochemical catalyst called polymerase, the machine would perform the process automatically on a target piece of DNA. The machine is so economical that even a small laboratory can afford it.
The selectivity of the PCR process, as well as the fact that it is simple and economical, have profoundly changed the course of research in many fields. In the field of genetics, the process has been particularly important to the Human Genome Project--the massive effort to map human DNA. Nucleotide sequences that have already been mapped can now be filed in a computer, and PCR enables scientists to use these codes to rebuild the sequences, reproducing them in a Thermal Cycler. The ability of this process to reproduce specific genes, thus effectively enlarging them for easier study, has made it possible for virologists to develop extremely sensitive tests for acquired immunodeficiency syndrome (AIDS), capable of detecting the virus at early stages of infection. There are many other medical applications for PCR and it has been particularly useful for diagnosing genetic predispositions to diseases such as sickle cell anemia and cystic fibrosis.
PCR has also revolutionized evolutionary biology, making it possible to examine the DNA of woolly mammoths and the remains of ancient humans found in bogs. PCR can also answer questions about more recent history. For example, it has been used to identify the bones of Czar Nicholas II of Russia who was executed during the Bolshevik revolution. Scientists at the National Museum of Health and Medicine in Washington, DC, are preparing to use PCR to amplify DNA from the hair of Abraham Lincoln, as well blood stains and bone fragments, in an effort to determine whether he suffered from a disease called Marfan's syndrome. In law enforcement, PCR has made genetic fingerprinting more accurate and effective; it has been used to identify murder victims, and to overturn the sentences of men wrongly convicted of rape. Some have suggested that PCR can be used to create tags or markers for industrial and biotechnological products, including oil and other hazardous chemicals, to insure that they are used and disposed of in a safe manner.
In 1986, Mullis left Cetus to work for Xytronyx, a San Diego research firm, where he became director of molecular biology. Two years later, he left to become a private biochemical research consultant. In 1993, Mullis won the Nobel Prize in Chemistry.
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