Nobel Laureate: Kary Mullis

 

The Nobel Prize in Chemistry 1993.

"for contributions to the developments of methods within DNA-based chemistry: for his invention of the polymerase chain reaction (PCR) method"


Kary B. Mullis (1944 - ) won the Nobel Prize in Chemistry for the polymerase chain reaction technique. This technique is used to amplify a given stretch of DNA by repeatedly copying it several dozen times. The technique has been honed and modified and it's now a standard tool in every biochemistry and molecular biology laboratory.

Mullis shared the prize with last week's Nobel Laureate, Michael Smith, who developed the technique of in vitro mutagenesis. I'm not a big fan of awarding Nobel Prizes to those who develop a new technique. I'm much more comfortable with awards to scientists who directly advance our understanding of how life works. That's why my personal favorites are Nobel Laureates like Jacques Monod, François Jacob, Ed Lewis, Otto Warburg, Linus Pauling, André Lwoff, Barbara McClintock, and Peter Mitchell (plus many others).

Fortunately, it usually turns out that the winners of "technology" prizes are very good scientists who have also made a significant contribution to advancing our knowledge of fundamental concepts. That's certainly true of Michael Smith, Walter Gilbert, and Fred Sanger, to name just a few.

Kary Mullis was an unusual recipient in many ways. You can get a flavor for his personality by reading his Autobiography and, especially, his Nobel Lecture. There has never been a speech like that in the history of the Nobel Prize and, chances are, there will never be another.

Read about Kary Mullis on Wikipedia to see what he's been up to since he stopped being an active scientist in 1988. By the time he was awarded the Nobel Prize he was concentrating on being a writer. (This might explain the speech!)

Here's the Press Release describing Kary Mullis' contribution.

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Nobel Laureates

The "Polymerase Chain Reaction" (PCR)

The PCR technique was first presented as recently as 1985 but is nevertheless already one of the most widespread methods of analysing DNA. With PCR it is possible to replicate several million times, in a test tube, an individual DNA segment of a complicated genetic material. Mullis has described how he got the idea for the PCR during a night drive in the Californian mountains. Two short oligonucleotides are synthesized so that they are bound correctly to opposite strands of the DNA segment it is wished to replicate. At the points of contact an added enzyme (DNA polymerase) can start to read off the genetic code and link code words through which two new double strands of DNA are formed. The sample is then heated, which makes the strands separate so that they can be read off again. The procedure is then repeated time after time, doubling at each step the number of copies of the desired DNA segment. Through such repetitive cycles it is possible to obtain millions of copies of the desired DNA segment within a few hours. The procedure is very simple, requiring in theory only a test tube and some heat sources, even though there are now commercial PCR apparatuses that manage the whole procedure automatically and with great precision.


The PCR method can be used for reduplicating a segment of a DNA molecule, e.g. from a blood sample. The procedure is repeated 20-60 times, which can give millions of DNA copies in a few hours.

As has site-directed mutagenesis, the PCR method has decisively improved the outlook for basic research. The sequencing and cloning of genes has been appreciably simplified. PCR has also made Smith's method of site-directed mutagenesis more efficient. Since it is possible with PCR to perform analyses on extremely small amounts of material, it is easy to determine genetic and evolutionary connections between different species. It is very probable that PCR combined with DNA sequencing is going to represent a revolutionary new instrument for studies of the systematics of plant and animal species.

The biomedical applications of the PCR method are already legion. Now that it is possible to discover very small amounts of foreign DNA in an organism, viral and bacterial infections can be diagnosed without the time-consuming culture of microorganisms from patient samples. PCR is now being used, for example, to discover HIV infections. The method can also be exploited to localise the genetic alterations underlying hereditary diseases. Thus PCR, like site-directed mutagenesis, has a great potential within gene therapy. Without the PCR method, the HUGO project, with its objective of determining every single DNA code in, among other things, the human genetic material, would hardly be realistic. In police investigations PCR can give decisive information since it is now possible to analyse the DNA in a single drop of blood or in a hair found at the scene of a crime.

Another fantastic application is that it is possible to mass-produce DNA from fossil remains. Researchers have, for example, succeeded in producing genetic material from insects that have been extinct for more than 20 million years by using the PCR method on DNA extracted from amber. This possibility has already inspired authors of science fiction. The very popular film "Jurassic Park" is about the fear that arises when researchers using PCR recreate extinct giant reptiles.

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[Photo Credit: Geschichte der PCR]