HAPPY ANNIVERSARY.

Fifty years after Watson and Crick's insight, scientists continue to take a close look at DNA's double helix. On April 25, 1953, a brief research paper appeared in the British scientific journal "Nature." Fifty years later, it's one of the most famous publications of all time and often considered the start of the molecular biology and genetics revolution that continues today. In that report, two young scientists at Cavendish Laboratory in Cambridge, England, proposed what they called a "radically different" structure for DNA, the material that scientists of the time had recently concluded stored an organism's genetic information. The pair argued that the DNA molecule resembles a spiral staircase. In the proposed arrangement, two strands are twisted together and connected at each step by a pair of so-called chemical bases, one jutting off each strand. On the eve of the 50th anniversary of the double helix's grand debut, "Science News" presents a gallery of images depicting the DNA molecule and, in one case, the genetic information it encodes.