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... the other side, a University of Maryland geneticust, S. Benson, comments, "Many people have had such observations, but they have problems getting them published." Our template in this discussion is an article by A.S . Moffat in American Scientist. She says, "The stakes in this dispute are high, indeed. If directed mutations are real, the explanations of evolutionary biology that depend on random events must be thrown out. This would have broad implications. For example, directed mutation would shatter the belief that organisms are related to some ancestor if they share traits. Instead, they may simply share exposure to the same environmental cues. Also, different organisms may have different mutation rates based on their ability to respond to the environment. And the discipline of molecular taxonomy, where an organism's position on the evolutionary tree is fixed by comparing its genome to those of others, would need extreme revision." What sort of experiment did Cairns do to cause such a ruckus? In particular, he studied E. Coli bacteria. Normally, these bacteria cannot metabolize the sugar lactose. Cairns exposed the E. Coli to a sudden dose of lactose, demonstrating that if the bacteria must have lactose to survive, they quickly cast off the two genes that inhibit their metabolizing of lactose. Of course, the experiments were more complicated than this, but the fundamental finding was that the bacteria mutated so that they could use lactose much, much faster than chance mutation would permit, stastically speaking. The battle lines are forming. A sup-porter of ...
Terms matched: 1 - Score: 14 - 15 May 2017 - URL: /sf064/sf064b07.htm
... humans and the great apes. Chromosome bandings are different enough to raise further suspicions about the 1.5 % figure. (Gibbons, Ann; "Which of Our Genes Make Us Human?" Science, 281:1432, 1998.) Comments. It is easy to see how gross comparisons of DNA might miss important details. The popular "DNA-hybridization" method simply mixes together strands of DNA from the two species being compared. These are allowed to combine, and then they are heated to see how much temperature is required to force them apart. Chromosome numbers and bandings have little if any effect on these crude comparisons of the bare DNA strands that have been stripped from their genes and chromosomes. The significance of all this transcends the comparisons of humans and chimps. Modern taxonomy of all life forms depends increasingly upon DNA comparisons rather than upon morphology. If DNA comparisons can be as misleading as they are in humans and chimps, those textbook family trees that are supposed to tell us how life evolved may also be giving us an erroneous history of life. To underscore the problem, sometimes DNA genetic differences do not result in big morphological changes. For example, Three-toed Woodpeckers hammer on trees all over the northern reaches of North America and Eurasia. These birds all look alike and interbreed freely. Yet, some of the birds differ so much genetically that they should be classified as different species on that basis. (See BBG1 in Biological Anomalies: Birds.) From Science Frontiers #122, MAR-APR 1999 . 1999-2000 William R. ...
Terms matched: 1 - Score: 14 - 15 May 2017 - URL: /sf122/sf122p08.htm
... that helps them ram their ways through the soil. In surface-living lizards this structure is merely a soft, flimsy cartilage. It was long assumed that the bone in the burrowing lizard developed from the cartilage of its surface-living kin. But a study of embryos now shows that the head bone of the burrowing lizard actually developed from a membrane instead of cartilage. The two similarly located structures are not homologous after all. They had different origins. Superficially this doesn't seem very anomalous and especially not very exciting. But vertebrate evolution in particular has been charted on the basis of homologous structures. If these structures have different biological origins -- even in just some cases -- the evolutionary family trees may be drawn wrong. (Anonymous; "Lizard Bone Shakes World of Taxonomy," New Scientist, 98:221, 1983.) Comment. No one yet knows how serious this problem really is. Basically it means that some animals that look alike (at least bonewise) need not be closely related. To use an analogy, if nature has the plans for a house stored in genetic material, it may be able to build that house out of wood, brick, or what ever material is available. From Science Frontiers #28, JUL-AUG 1983 . 1983-2000 William R. Corliss ...
Terms matched: 1 - Score: 13 - 15 May 2017 - URL: /sf028/sf028p11.htm
... formation." (Meaden, G.T .; "Sheep in Circular Flocks: Is There a Meteorological, or Some Other, Connection?" Journal of Meteorology, 14:54, 1989. Journal address: 54 Frome Road, Bradford-on-Avon, Wiltshire, ENGLAND BA15 1LD.) Comment. In his letter, Belcher wondered what mysterious force had arrayed the two flocks of sheep so neatly. Meaden, very timidly to be sure, ventured that the same sort of whirlwinds that he believes cuts the crop circles might cause sheep to drift outwards into a circle! In the interest of complete-ness, some grazing animals, such as the muskoxen, will form into a circle when threatened. But are there appropriate whirlwinds in the Arctic? So much for deprecating taxonomy-through-morphology! From Science Frontiers #64, JUL-AUG 1989 . 1989-2000 William R. Corliss ...
Terms matched: 1 - Score: 13 - 15 May 2017 - URL: /sf064/sf064b06.htm
