New paths in genetics / by J.B.S. Haldane.

  • Haldane, J. B. S. (John Burdon Sanderson), 1892-1964.
Date:
1941
Catalogue details

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

Credit: New paths in genetics / by J.B.S. Haldane. Source: Wellcome Collection.

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    The Science of Genetics among others. A single unit character may only develop in the presence of many genes. Thus at least two dominant genes must be present before colour develops in Matthiola^ and these two, and two more as well, must be present before hairs are formed. Secondly, the effect of a given set of genes is in no way absolute, but depends on the environment. Thus certain human skins are almost unpigmented when not exposed to strong radiation, but in summer some develop freckles whilst others become a more uniform brown. The pigmentation of the feet, ears, and nose of the Hima¬ layan rabbit depends on cold. Genes responsible for chlorophyll production in plants only achieve this end in presence of light and of iron salts, and so on. Thirdly, the modern interpretation of morphological facts is more and more in terms of processes rather than end results. For example, Vogt^ has shown that one can homologize the processes of gastrulation throughout the Chordata, but as the temporal order of these processes may vary, one cannot homologize the forms which result from their interaction. For these reasons Hagedoorn was already thinking of genes as determining processes nearly thirty years ago, and to-day it is beginning to be generally realized that we shall come nearer the truth if we regard the gene as responsible for a unit process than for a unit character. I do not, of course, suggest that this concept is anything ^ Vogt, W. (1929), ^rcÄ. Entwicky 120. 21