Born in Lenoir, North Carolina, Mullis was educated at Georgia Institute of Technology and at the University of California, Berkeley, where he completed his PhD in 1973. After postdoctoral periods at the University of Kansas Medical School and at the San Francisco campus of the University of California, Mullis joined the Cetus Corporation of Emeryville, California, in 1979.

One Friday night in April 1983 while driving to his weekend cabin, Mullis has recorded, it suddenly struck him that there was a method of producing unlimited copies of DNA fragments simply and in vitro (i.e., outside living cells). Previously, fragments could only be produced in limited numbers, in cells, and with much effort. Mullis named his method the ‘polymerase chain reaction’ (PCR). The significance of the reaction can be judged by the price of $300 million placed by Cetus on the PCR patent sold to Hoffman-La Roche in 1991.

The first stage of the process is to heat DNA containing the required genetic segment in order to unravel the helix. Primers can then be added to mark out the target sequence. If, then, the enzyme DNA polymerase together with a number of free bases are added, two copies of the target sequence will be produced. These two copies can then be heated, separated, and once more produce two further copies each. The cycle, lasting no more than a few minutes, can be repeated as long as supplies last, doubling the target sequence each time. With geometric growth of this kind, more than 100 billion copies can be made in a few hours.

Relations between Mullis and Cetus quickly soured. He left the corporation in 1986 to work for a plastics manufacturer. But as the importance of his work began to be recognized Mullis found himself in sufficient demand to warrant his setting up as a consultant. One of his clients was Cetus as they fought off challenges to the PCR patent from DuPont and others. Mullis himself claims to be “tired of PCR” and more interested in “artificial intelligence, tunneling microscopes, science fiction, and surfing lessons.” For his work on PCR, Mullis shared the 1993 Nobel Prize for chemistry with Michael Smith.