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DNA and pulsar research win 1993 Nobels.

Methods that enhance the study of genetic material and the discovery of an unusual type of star garnered this year's Nobel Prizes in Chemistry and Physics.

In physics, Russell A. Hulse, 42, and Joseph H. Taylor Jr., 52, both at Princeton University, were cited for their discovery of a binary pulsar -- a pair of rotating neutron stars that has a illuminated the study of gravity waves in the universe. In chemistry, Kary B. Mullis, 48, formerly with Xytronyx Inc. in La Jolla, Calif., and Michael Smith, 61, at the University of British Columbia in Vancouver, will share the $825,000 prize for the powerful DNA research techniques each developed.

In 1974, Hule and Taylor used the 300-meter radio telescope at Arecibo, Puerto Rico, to monitor the beacon-like emissions of a pulsar. This stellar object, called PSR 1913+16, emits bursts of energy about 17 times a second with a steadiness comparable to that of the best atomic clocks. Noticing oddities in the pulsar's emission cycle -- believed at the time to be caused by one rapidly rotating neutron star -- Hulse and Taulor figured out that a second, companion star must be involved. In fact, the second star of this stellar system has one and a half times the mass of the sun compressed into a ball only 20 kilometers in diameter.

Moreover, by timing signals from the binary pulsar over many years, physicists have further verified aspects of Einstein's theory of general relativity. At a barely detectable level, the two stars are spiraling toward each other orbiting more quickly -- a rate change of only 75 milli-seconds per year. But the energy loss in the binary system is significant, falling in line with Einstein's predictions, if one assumes the pulsar emits gravity waves. Thus, many physicists see PSR 1913+16's behavior as good evidence for the existence of these otherwise unseen waves.

Smith's 1978 invention of oligonucleotide-based, site-directed mutagensis has enabled scientists to "reprogram" the genetic code by the changing the order of specific nucleic acid -- the building blocks of DNA. The altered DNA then spawns changed proteins, whose actions differ from those of the original proteins.

Scientists had long sought to use nature's own process of mutation to their research advantage. But it was Smith who, during a coffee break at the University of Cambridge in England, conceived of a controlled method of harnessing these DNA coding errors. He saw a way to incorporate tailor-made DNA fragments into a host organism, where they would replicate. Today, researchers use site-directed mutagenesis to "design" proteins, treat genetic diseases, and create medically and commercially useful items such as hemoglobin-enhanced red blood cells, immune cells that attack cancers, and disease-resistant plants with unique qualities.

Mullis received the award for his 1985 invetion of the polymerase chain reaction (PCR), now a basic tool of the biotechnology industry. PCR is used to amplify minute samples of DNA in solution by rapid, million-fold replication. During a moonlit mountain drive, Mullis envisioned a way to have one strand of a DNA double helix split and replicate repeatedly, cycling up to 60 times in a few hours. In each PCR cycle, heating causes the interwined DNA to split into two separate strands. Then, with the help of the enzyme DNA polymerase, the strands replicate themselves from DNA fragments added to the solution.

By the 20th cycle, more than I million copies of the original DNA sample exist. Thus, scientists can quickly test for the presence of an infectious agent, such as HIV, or help place criminals at the scene of the crime with a single drop of blood or strand of hair -- as part of the process known as DNA fingerprinting. The PCR technique makes possible in-depth genetic studies of plants, animals, and humans, as well as reconstructions of fossilized DNA preseved for millions of years in insects trapped in amber (SN: 10/24/92, p.280). The Royal Swedish Academy of Sciences even acknowledged the movie "Jurassic Park" as a fictional outgrowth of Mullis' PCR technique.
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Title Annotation:Nobel Prizes in Chemistry and Physics
Author:Lipkin, Richard
Publication:Science News
Date:Oct 23, 1993
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