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No. 41: Sep-Oct 1985

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Genetic Garrulousness

It is tempting to predict that those cells with the most genetic material will belong to the most advanced organisms. One would, for example, expect to find more DNA or nucleotide pairs in human cells than the cells of bacteria or plants. In the case of the bacteria, this expectation is realized. Some plants, however, have one hundred times more DNA per cell than humans. Some fish and salamanders do, too.

One reason why there is no simple relationship between a cell's genetic complement and the organism's complexity is that a lot of genetic material is apparently useless, with no known functions. Human genes, by way of illustration, possess about 300,000 copies of a short sequence called Alu. The Alu sequences seem to be simply dead weight -- functionless -- yet continuously reproduced along with useful sequences. One purposeless mouse gene sequence is repeated a million times in each cell.

(Stebbins, G. Ledyard, and Ayala, Francisco J.; "The Evolution of Darwinism," Scientific American, 253:72, July 1985.)

Comment. Why so much redundance? Or is there some purpose for this excess genetic material that we haven't yet descried? The "useless" sequences may merely be left over from ancient gene shufflings; or they may be awaiting future calls to action. The above tidbits come from a long review article that is generally supportive of the modern theory of evolution. (Would it have been printed in Scientific American if it weren't?) The article also treats the Neutral Theory of Evolution, noting that this theory still depends upon natural selection operating at the phenotype (organism) level.

From Science Frontiers #41, SEP-OCT 1985. 1985-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:

Quotes

  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987