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Mullis, Kary (Banks)

dna polymerase genes method

(1944– ) US biochemist: devised the polymerase chain reaction for amplification of traces of DNA.

Mullis studied chemistry at the Georgia Institute of Technology and then biochemistry at Caltech, and afterwards joined a biotechnology company, Cetus.

His fame and the Nobel Prize for chemistry which he shared in 1993 stem from an idea that came to him during a 3-hour night drive in 1983. This concerned the problem of identifying genes (or other fragments of DNA), especially when only a small sample is available. His scheme was to first break up the DNA by a known technique using restriction endonucleases, which split the DNA at specific base-pairs to give a mixture of oligonucleotides: these are of modest molecular size (a few dozen base-pairs) and contain the genes, in the form of specific base sequences.

The Mullis idea was to take these oligonucleotides and use a chemical method whereby they replicated themselves, employing relatively uncomplicated reagents and allowing the synthesis to proceed repetitively on the products. His method for doing this was subtle but experimentally simple (a ‘one-pot’ cycle of reactions whose result would be to continually amplify the starting oligonucleotide). Each cycle, doubling the DNA fragments, took only 1–2 minutes, so in a few hours one molecule gave 100 billion replicas of itself. A key material, used as a catalyst, was DNA polymerase, discovered by in 1955. Within a year Mullis had tested and improved the method; he named it the polymerase chain reaction (PCR); it has been widely used ever since. These uses include very sensitive tests for genes, based on PCR’s ability to amplify a trace of DNA to a handlable quantity, valuable in forensic work to identify a small hair or semen sample and in studies on DNA traces from extinct fossil animals, such as insects trapped in ancient amber, and from dinosaur bones.

His recorded interests include artificial intelligence, computing, photography and cosmology. Mullis has acquired a notable reputation as an eccentric. Never a conformist, he doubts if the HIV virus alone causes AIDS. Now an independent consultant, he set up a company (Stargene) to make and market amplified samples of the DNA of entertainment stars, in lockets and bracelets. He believes Nobel Prizes should be home-delivered by royal messenger.

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