Word: rna
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Biology students used to be taught that there was a strict division of labor within living cells. The nucleic acids, DNA and RNA, served as repositories of genetic information, and certain proteins, called enzymes, did all the work. But research conducted in the past decade by Sidney Altman of Yale University and Thomas Cech of the University of Colorado at Boulder has forced scientists to alter completely their ideas not only of how cells function but also of how life on earth began. Last week the Nobel Prize for Chemistry went to Altman and Cech, with the citation that "many...
FOOTNOTE: *A virus consisting largely of RNA, a single-stranded chain of bases similar to the DNA double helix...
...virus, whether biological or electronic, is basically an information disorder. Biological viruses are tiny scraps of genetic code -- DNA or RNA -- that can take over the machinery of a living cell and trick it into making thousands of flawless replicas of the original virus. Like its biological counterpart, a computer virus carries in its instructional code the recipe for making perfect copies of itself. Lodged in a host computer, the typical virus takes temporary control of the computer's disk operating system. Then, whenever the infected computer comes in contact with an uninfected piece of software, a fresh copy...
...like the head of a Roman mace, with spikes protruding in all directions; herpes viruses are spherical, as is the AIDS variety. Whatever their shape, all viruses have something in common. They are models of biological minimalism, consisting simply of a core of genetic material -- either a DNA or RNA molecule -- and a protective envelope made of proteins (most varieties have a double coat, the outer one consisting either of another protein shell, or of proteins and lipids, fatty substances similar to those in a cell membrane). "There's no waste in a virus," says Dr. Stephen Straus...
Some DNA viruses become inactive and escape detection by the host's immune system by insinuating their genetic material into the DNA of the host cell. A retrovirus, however, must first use its enzyme called reverse transcriptase to convert its RNA into a DNA molecule, which can then insert itself into the cell's DNA and order the cellular machinery to begin producing more retroviruses. Or it can remain dormant and invisible to the immune system, / awaiting some signal to begin causing trouble. Hidden in the cell's DNA, says David Baltimore, who shared a Nobel Prize for the discovery...