Paradigm shift examples1/30/2024 The first codon (UUU=phenylalanine) was elucidated in 1961 (Nirenberg and Matthaei). Second, the sequence of nucleotides (the basic building blocks of DNA and RNA, consisting of a nitrogenous base, a five-carbon sugar, and at least one phosphate group) in the DNA polymer contained information, a genetic code, determining the sequences of amino acids in proteins and, eventually, the structure and the function of the protein. This was demonstrated to be the case in 1958 (Meselson and Stahl). That model made two clear predictions: The double helix would replicate in a semi-conservative fashion, separating the two parental strands of DNA, which could then act as templates using base pairing. Watson and Crick (1953) built a model of DNA using Rosalind Franklin’s X-ray data and Erwin Chargaff’s rules. The new molecular biologists would look forward to the sequences of those chemicals that made up DNA as the proper study of evolution. From 1953 to 1968, a generation of young biologists were passing through Thomas Kuhn’s paradigm shift from organismic biology, celebrated in the Guyot museum, to molecular biology, viewing life at the molecular level and asking questions that often ignored the organism, its natural life cycle, and its interactions with the environment. It was a great biological museum, dedicated to a biology that began in 1859, when Darwin published his book On the Origin of Species, and stretched to 1953, when Watson and Crick published a paper on the structure of DNA. The diversity and varieties of animals selected by Darwinian evolution over the geological ages were in evidence, extolling the unity of all organisms and the central tenets of geology and biology. Plates that Audubon used to etch images of his birds and print his beautiful books hung on the walls. Among the questions under study in the laboratory were: how many genes did the virus devote to causing cancer? How did the proteins encoded by these genes function to initiate and to maintain a tumor? What were the molecular mechanisms involved? The Moffett laboratory building was a newer extension to Guyot Hall, which had been built in 1909 for the Geology and (then) newly created Biology Department.Ī great deal of the space at the entrance of the building was taken up with stuffed animals, jars filled with formalin containing suspended embryos, skeletons of animals that no longer exist, and plants imprinted into rocks millions of years ago. Schooled and trained over the previous seven years in the reductionist approaches of Watson and Cricks’ molecular biology, he moved into the Moffett Laboratory to study how the simplest of organisms, a virus, could cause cancer in a mouse or in a hamster. In the summer of 1968, a young, newly minted assistant professor moved from a postdoctoral position at Caltech to Princeton University.
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