The facts of life / C.D. Darlington.

  • C. D. Darlington
Date:
1953
Catalogue details

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

Credit: The facts of life / C.D. Darlington. Source: Wellcome Collection.

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    the production of our germ cells. They do not blend. The germ cells therefore contain one of the two alternative factors responsible for, or connected with, each character and are therefore pure in respect of differences between alternative characters for which the parent may be hybrid or impure. The second law is that the members of different pairs of factors responsible for different characters are segregated and recombined independently in different germ cells. True it is, of course, that these laws made it possible to throw a large part of the supposed common sense of mankind on the subject of heredity, and all the superstitions from Aristotle to Lamarck, on to the rubbish heap. Pangenesis and the inheritance of acquired characters were left suspended in meaningless contradiction. Blending inheritance was seen to be a misinterpretation. The mixing of characters left them entirely uncontaminated for posterity. Prepotency was not a property of individuals, or of breeds, or of one or other of the sexes, but of a character-difference, or perhaps even of something behind the character-difference. The contributions of male and female were equal; reciprocal crosses were alike. Everything else in heredity was a property not of the parents but of their germ cells and thus had to be recorded statistically, and interpreted in terms of sampling. Reversion was due to segregation. And recessive characters appearing by segregation, although arising from something in the parents, need not have been inherited in the sense that any ancestor has shown them. The most momentous of such characters is sterility, and Mendel had shown how it could happen that all sterile plants and animals have had fertile parents. Their sterility is genetically determined but it is not inherited in the popular sense. What was to be hereditary in the future had not, therefore, necessarily been hereditary in the past. This last principle of latency had been perceived by Galton. But Mendel had explained it. Singly these revelations were impressive. Taken together they were staggering. We may say that students of biology have never entirely recovered from the impact. But even lOI