Word: rna
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Ungar and other researchers strongly suspect that the chemical mechanism for such learning is governed by RNA molecules in the brain cells. By directing the assembly of the body's 20 or so amino acids into the proper combinations, these master molecules are apparently able to make an imprint of a memory or learning experience. Ungar is convinced that chemical processes similar to those in the brains of his rats also occur in the brains of higher animals, including man. If this is indeed true, it may eventually be possible to enhance man's knowledge and to treat...
...cells of 48 healthy people and three leukemia patients, Gallo and two colleagues−Stringner S. Yang and Robert C. Ting of the Bionetics Research Laboratories−discovered a small but possibly critical difference. The white cells of the leukemia victims showed the presence of an enzyme known as RNA-dependent DNA polymerase; the cells of the normal people did not. The presence of the enzyme suggested that it may play a key role in the development of the disease...
...support the iconoclastic ideas of Howard Temin, a University of Wisconsin molecular biologist who long espoused what his colleagues considered a major heresy. According to accepted theory, the hereditary information in the chromosomes of all cells passes in the same direction. Double-stranded DNA molecules make single-stranded messenger RNA molecules, which then direct the production of proteins, the basic building blocks of every cell. Temin contended that the process is sometimes reversed: RNA, he insisted, could make DNA. Otherwise, he asked, how could cancer-causing viruses−which consist of bundles of RNA sheathed in protein−inject their...
Last summer Temin and other molecular biologists produced strong experimental evidence that RNA viruses may indeed be capable of producing their own DNA (TIME, July 20). Columbia University's Sol Spiegelman confirmed it. He demonstrated how an enzyme, or natural chemical catalyst, can cause tumors in laboratory animals by a DNA-RNA reversal. As Temin had postulated, the enzyme turned out to be RNA-dependent DNA polymerase. But a question remained: Was the same enzyme also present in human cancer...
Major additions in the areas of DNA replication and DNA and RNA viruses are sure to attract some attention. Students who took Nat Sci 5 or Bio 2 or any other introductory biology course before this year and think they learned about DNA replication in those classes will be surprised by Watson's new chapter on DNA duplication. DNA replication is often presented as the unwinding and subsequent rewinding of linear complementary ploy-nucleotide strands of DNA. However, this chapter now offers the Rolling Circle model of DNA replication, a complex model of revolving, duplicating circular DNA strands. Evidence...