Sir Sebright effect at the individual level

The Sir Sebright effect can also apply at the individual level to organisms without a Weismann barrier. Lysenkoists described experiments in which two plants cultivated by cloning from a single rhizome were crossed together. They stated that the progeny obtained are more viable when the two plants were grown under different conditions, e.g. one in dry and one in damp soil, than if they are grown under the same conditions (Turbin 1952, p. 138). It is quite possible that the Lysenkoists thought up this result, similar to a great many others. However, it is also possible that the Sir Sebright effect was manifested in their experiments, i.e. that intra-organism cell-line selection selected genetically different cell lines of the parent plants under different conditions and that genetically different germinal cells gradually formed from them. The combination of genetically different germinal cells subsequently led to the formation of more viable progeny than would have been formed by combination of genetically more similar germinal cells derived from plant clones kept under the same conditions. In addition to classical somatic mutations, the source of variability for intra-organism selection could, of course, also have been epigenetic changes (see II.8).

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more