Mullis, Kary Banks (1944-2019), an American biochemist , created the technique of DNA amplification—copying minute quantities of deoxyribonucleic acid ( DNA ), the genetic material of life, billions of times over. The ability to do this lies at the root of all the techniques that involve working with traces of DNA, such as studying the past by examining DNA remnants, analyzing crime-scene evidence through DNA “fingerprinting,” using medical processes to diagnose and repair genetic defects, and modifying agricultural plants and animals. Mullis shared the 1993 Nobel Prize for chemistry with Michael Smith of Canada, who worked in other areas of the biochemistry of genes .
Mullis was born on Dec. 28, 1944, in Lenoir, North Carolina. He received a bachelor’s degree in chemistry from the Georgia Institute of Technology in 1966, having set up his own company manufacturing chemicals while he was a student there. He received a doctorate in 1972 from the University of California at Berkeley for research in biochemistry.
In the late 1970’s, Mullis took a job at the Cetus Corporation, a biotechnology firm in California. His work involved synthesizing nucleotides—short stretches of DNA. In 1983, he had the idea of developing a technique for identifying particular nucleotides at particular locations in a stretch of DNA. In the attempt to devise this technique, he came up with the idea for a process that would achieve something quite different: the copying in abundance of a small sample of DNA. See Heredity (The structure of DNA) .
Mullis developed his process, which he named the polymerase chain reaction (PCR), over several years. The PCR technique begins with heating the original double-stranded DNA to cause the strands to separate. Then a primer, consisting of a sequence of a few nucleotides, is attached to a strand. Four types of nucleotides, the raw materials of the new DNA, are added, together with RNA polymerase, an enzyme (material that promotes reactions among other materials). The process then mimics the natural process of copying DNA, which happens in the replication of living cells. A chain of nucleotides is built up, beginning with the primer and forming a second strand of DNA attached to the first. When the process has finished, the two strands of the original DNA have been replaced by two double strands. These can be warmed to separate them, and the process can be repeated. Running through the cycle 40 times multiplies the amount of DNA present by a trillion times. Such quantities are needed to enable the DNA to be studied or to be used in any of the applications that involve DNA. See Polymerase chain reaction (The PCR process) .
By the end of 1985, Mullis published the first description of the PCR technique. In 1987, Cetus patented the process. Mullis had by then left the company, in conflict with it over the amount of credit he received and over control of his research. Mullis died on Aug. 7, 2019.
