Word: helix
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...deoxyribonucleic acid) that carries in it the traits of heredity. When its home cell begins to divide, the DNA performs wondrously: its complicated molecules, ordinarily like two ropes twisted together, untwist and separate. Each rope attracts bits and pieces from fluid around it and forms a new double helix like the original one. Apportioned between the halves of the dividing cells, the duplicated DNA molecules determine whether the new individuals will be men or muskrats, pine trees or pineapples. The hereditary characteristics of the next human generation-of about three billion people-will be controlled by one fifteen-thousandth...
...Chemist Linus Pauling, who won a Nobel Prize for his work on molecular structure, reported that the DNA molecule has a helical (spiral-staircase) structure. Later that year, James D. Watson and Francis H.C. Crick in England went a step farther. DNA, they said, is a double helix with two spirally rising chains of linked atomic groups and a series of horizontal members, like steps, connecting the two spirals. This molecular model, deduced mostly from X-ray diffraction photos, seemed complex and unlikely, but geneticists rejoiced when they heard about it. It was just what they" needed to explain many...
Here, the geneticists now believe, lies the high command of growth and reproduction. Double-helix DNA molecules, thousands of turns long and arranged by thousands in each chromosome, can carry a vast amount of coded information. They may very likely carry enough to determine whether a fertilized egg grows into a clam or an elephant. When chromosomes replicate during cell division, the DNA molecules that they contain presumably replicate...
Natural Balance. Similarly, the Helix snail, presumably imported from Europe, did not become a hazard to citrus groves until it reached California. In effect, what the biologists hope to do is restore a natural balance, which was upset when the Helix left home...
...keeping native California snails in check. Why import a foreign variety? In reply, Clausen points to the fact that California snails have generally stuck to wild areas, and presumably could not be coaxed into orchards. More over, says Clausen, he does not fear that the Gonaxis will devour the Helix and turn to other food. Long before that happens, the law of supply and demand will take over, freezing the population of both hunter and hunted at a safe level...