THE BEST SCIENCE OF 1993

1 The Great Gene Hunt. It was an extraordinarily productive year for the genetic engineers racing to unravel the secrets of human DNA. Scientists not only pinpointed genes linked to more than half a dozen major ailments -- including Lou Gehrig's disease, Huntington's disease, colon cancer, hyperactivity and a type of diabetes -- but also sketched out the first rough map of all human chromosomes. Other researchers explored ways to use this information to replace damaged genes. The first beneficiaries of ''gene therapy'' -- two Ohio girls who have an immune-deficiency disease -- made their public debut after three years of successful treatment. More than 50 similar experiments are under way.

2 Hubble Rescued The Endeavour astronauts played Mr. and Ms. Goodwrench in space -- and on live television -- performing daring orbital repairs on the nearsighted Hubble Space Telescope and giving beleaguered NASA a badly needed boost.

3 Dark Matter Discovered For nearly a decade, scientists had been searching for dark matter -- the mysterious stuff whose gravity seemed to hold the universe together but which nobody had ever seen. This year they found it -- or at least some of it -- in the form of Jupiter-like clumps of matter known as massive compact halo objects, or MACHOS.

4 Fusion Breakthrough The hottest place in the solar system -- for a few moments -- was the interior of a huge doughnut-shaped contraption at the Princeton Plasma Physics Lab, which in a burst of heat and light generated more than 5 million watts of energy, a record for nuclear fusion and a milestone on the road to making power plants fueled by ingredients from ordinary water a 21st century reality.

5 Fermat's Last Theorem The puzzler that stumped the world's greatest mathematical minds for 350 years was finally solved by Princeton's Andrew Wiles -- or was it? Like French mathematician Pierre de Fermat, who claimed to have discovered a marvelous proof he couldn't fit in the margin of his notebook, Wiles has run into a last-minute problem but says he is sure he can resolve it.

6 Ancient Genes The premise of Jurassic Park -- that material from blood cells found in the thorax of a prehistoric fly might be cloned to re-create a living dinosaur -- was echoed eerily in the science journals. Not only did scientists extract bits of DNA from the bone marrow of a 65 million-year-old Tyrannosaurus rex fossil, but they also recovered intact DNA from an insect trapped in amber back in the Mesozoic era, 130 million years ago.

7 Biospherians Emerge They may have been the butt of countless Leno and Letterman jokes, but the eight men and women of Biosphere II did what they said they would do: they spent two years locked inside the world's largest terrarium and managed, despite some pretty flaky methodology, to make a significant contribution to ecological science.

8 Human Embryos Cloned Two U.S. researchers made copies of human embryos and nurtured them in a Petri dish for several days. The project was not the ''cloning'' of a Hitler or a Michael Jordan that ethicists and science-fiction writers had fantasized about, but it was close enough to launch a worldwide debate over whether science had finally gone too far.