History of Genetics - Rediscovery
Science EncyclopediaScience & Philosophy: Heterodyne to Hydrazoic acidHistory of Genetics - Gregor Johann Mendel, Rediscovery, The Chromosome Theory Of Heredity, Culture Of Heredity, Fine Structure Of The Gene
In 1900 three European botanists, Hugo de Vries, Carl Correns, and Erik Tschermak, published the results of their experiments carried out in the 1890s that supported Mendel's experimental results and his conclusions. Although the first two had in fact seen Mendel's paper earlier, its significance had not struck them. Only later, when they had their own results, did they encounter his paper again and realize its importance. In England the Cambridge zoologist William Bateson teamed up with the Reverend William Wilks, secretary of the Royal Horticultural Society, and Maxwell Masters, chairman of the society's scientific committee, to spread the word about Mendel. Through this prestigious and influential society Bateson introduced Mendel's work to the English-speaking world, and the Reverend Wilks asked Charles Druery, a hybridist and fellow of the society, to translate Mendel's paper into English for its publication in the society's journal.
It was at the Royal Horticultural Society's Third International Conference on Hybridisation and Cross-breeding that Bateson introduced the term "genetics" to the audience gathered in London in 1906. When the conference proceedings appeared Wilks had renamed it Report of the Third International Conference 1906 on Genetics: Hybridization.
British biologists were for the most part unreceptive to Mendel's work. Karl Pearson, upholder of Galton's biometric tradition, was opposed. Darwinians like Alfred Russel Wallace were appalled, and the Oxford professor Edward B. Poulton reported the consensus he had found among eminent zoologists that Mendelian writings were "injurious to Biological Science, and a hindrance in the attempt to solve the problem of evolution." According to Pearson, the Mendelian theory was not conformable with the statistical data he was amassing on the relation between successive generations (the regression coefficients). It took the insight and persistence of the young Ronald Aylmer Fisher (1890–1962) to remove this roadblock to the integration of Mendelism and biometry. His solution of the problem finally appeared in 1918.
The biometricians' theory was ancestrian, meaning that the hereditary constitution of offspring was considered to be a collection of representations from the ancestors, the proportions of which are based on some form of the old fractional theory. This was formulated under the title "The Ancestral Law of Inheritance." Confining their attention to what is visible, the biometricians were not concerned with so-called hidden elements. As a positivist, Karl Pearson was particularly concerned not to invent or invoke unobservable entities like Mendelian factors. Mendelians, by contrast, were opening up the space between the hereditary determinant (Mendelian factor) and the observable character or characters for which it is responsible. Mendel's language of the transmission of characters was giving place to the Mendelians' growing reference to the transmission of factors.
Powerful opposition to the biometricians came not only from Bateson in England but from Wilhelm Johannsen in Denmark. He complained that the biometric approach was based on the assumption that the "personal qualities" of an individual "are the true heritable elements or traits." But this, he declared, "is the most naïve and oldest conception of heredity" and can be traced back to Hippocrates. It was, he claimed, borrowed from the legal language of inheritance and heirs to property. As such it includes not only long-standing possessions but what has been acquired by the testator in his or her lifetime. But in biology the evidence was against acquired characters being heritable, and the modern view of heredity was that the "sexual substances" in the egg and sperm determine the personal qualities of the individual, not the reverse. To banish these confusions Johannsen proposed a new language for heredity in the form of the "gene," "genotype," and "phenotype." "The gene," he explained, "is nothing but a very applicable little word, easily combined with others, and hence it may be useful as an expression for the 'unit-factors,' 'elements,' or 'allelomorphs' in the gametes, demonstrated by modern Mendelian researchers. A 'genotype' is the sum total of all the 'genes'" in a germ cell or fertilized egg. Avoiding speculation as to the nature of the gene, he felt that "the terms 'gene' and 'genotype' will prejudice nothing" (Johannsen, p. 133). But just as it took a long time for the term genetics to become generally established, so was the case for Johannsen's terms.
- History of Genetics - The Chromosome Theory Of Heredity
- History of Genetics - Gregor Johann Mendel
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