The Nobel Prize in Chemistry 1993 was awarded "for contributions to the developments of methods within DNA-based chemistry" jointly with one half to Kary B. Mullis "for his invention of the polymerase chain reaction (PCR) method" and with one half to Michael Smith "for his fundamental contributions to the establishment of oligonucleotide-based, site-directed mutagenesis and its development for protein studies".
 

The applications of Mullis' PCR method are already many. The method offers new possibilities particularly in medical diagnostics, and is used, for example, for discovering HIV virus or faulty genes in hereditary diseases. Researchers can also produce DNA from animals that became extinct millions of years ago by using the PCR method on fossil material.
 

The genetic code programmed into the DNA molecule determines the number and sequence of amino acids in a protein, and thus also the functional properties of the protein. With Smith's method it is possible to re-programme the genetic code and in this way replace specific amino acids in the proteins. This is termed site-directed mutagenesis.