Heredity east and west : Lysenko and world science / Julian Huxley.

  • Huxley, Julian, 1887-1975.
Date:
1949
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Heredity east and west : Lysenko and world science / Julian Huxley. Source: Wellcome Collection.

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    HEREDITY EAST AND WEST which are not. The latter we call modifications. Modifica¬ tions are of two somewhat distinct sorts, the one due to dif¬ ferences in environment, such as the darker skin-color of white men who have been exposed to plenty of sun, the other due to differences in habits or activity, such as the greater muscular development that comes with heavy work. But all modifications have this in common, that in the first instance they affect the individual body and its organs, and not the reproductive cells. In the second place, neo-Mendelism has established that the variations originating in the hereditary constitution are due to mutations. A mutation is a change of measurable ex¬ tent in the constitution—either a change in quality of a single gene, or a change in quantity due to the addition or subtrac¬ tion of whole genes, sections of chromosomes, whole chro¬ mosomes, or whole chromosome-sets. A small part of this sort of variation, as it exists at any one moment, is due to fresh mutations, but most of it is due to old mutations (giv¬ ing rise to mutant genes which have then become stored in the hereditary constitution), and to the combination of mutated genes with each other and with unmutated genes. The existing difference between a natural blonde and a nat¬ ural brunette depends on a difference in a few kinds of genes, blondes and brunettes possessing different allels of these genes. But it is of mutational origin, due to some of the original allels having mutated into slightly different ones; and this holds good even though the blonde, through modifi¬ cations acquired by intensive sun-bathing, might become as dark as the brunette. Here I must diverge a moment to clear up a common mis¬ understanding, that neo-Mendelism denies any influence to 6