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FRAGMENT FROM NATURE continues from last weekend and concludes this weekend on a wonderful article about the history of the differences in philosophy between geneticists and embryologists that led to conflicts before the two disciplines came together. The two groups were founded in reductionism and holism respectively, and the two viewpoints were largely unreconcilable. Because of this they took up different camps in the cell and followed different theories. https://lnkd.in/dQuxg6Y View in LinkedIn

PLASMAGENES. “The cytoplasm is seen to act directly on the genes and not on their intermediate products. After reviewing enzymatic adaptation (and calling it that), Stern claims that there is no convincing evidence for the existence of the postulated plasmagenes.” https://lnkd.in/dQuxg6Y View in LinkedIn

THE NEW ALCHEMY. “According to Lvtrup and colleagues (1978), "few compounds, other than the philosopher's stone, have been searched for more intensely than the presumed agent of primary embryonic induction in the amphibian embryo.” https://lnkd.in/dQuxg6Y View in LinkedIn

SEQUENTIAL INDUCTION. “The exposure of an organism to a single inducer which is also a substrate may result in the induction of a sequence of enzymes, since the metabolism of the primary inducer gives rise to the formation of a succession of intermediary metabolites each of which serves as an inducer for the enzyme which converts it to the next member of the metabolic chain. This phenomenon is termed 'sequential induction' (simultaneous or successive adaptation)." https://lnkd.in/dQuxg6Y View in LinkedIn

Examples of two different stone wall finishes in Girona, two out of dozens of standard types. View in LinkedIn

THE ROOT OF THE PROBLEM. “Jean Baptiste Lamarck in 1809 proposed his concept that all living things, through the process of evolution, strive for perfection.” https://lnkd.in/da7dRTF View in LinkedIn

NOMENCLATURE CHANGE. “No longer would the term adaptive enzyme be used, for the term "adaptive" denoted a change which increased the evolutionary fitness of the organism. Rather, the process would be known as enzyme induction and "any substance thus inducing enzyme synthesis is an enzyme 'inducer.' An enzyme-forming system which can be so activated by an exogenous inducer is 'inducible'.” https://lnkd.in/dQuxg6Y View in LinkedIn

IMPACT OF COMPETITION FOR RESOURCES. “This would lead to the canalization of development and would explain the stability and irreversibility of differentiation. This is what Spiegelman had also noted. Waddington noted that others such as Darlington, Lindegren, Spiegelman, and Sonneborn, have proposed such self-duplicating plasmagenes on genetic evidence, but that this type of entity fit in well with the observed facts of embryology.” https://lnkd.in/dQuxg6Y View in LinkedIn

COMPETITION FOR RESOURCES. “In such circumstances, comparatively slight changes in the available raw materials might shift the whole dynamic system from one path into another. The progressive substrate changes would lead to changes in new enzyme synthesis, which would, in turn, create further substrate changes.” https://lnkd.in/dQuxg6Y View in LinkedIn

VICTORY LAP. “Indeed, reading Moore, one gets the impression that the lac operon model was a victory of the embryological view over the genetic.” https://lnkd.in/dQuxg6Y View in LinkedIn