From "Pangenesis" to "Genome".

The term “genetics” has been used in reference to the branch of science dealing with “the physiology of heredity and variation” since 1905. It was coined by the British biologist William Bateson, first in a 1905 letter (see Bateson 1928), and then publicly the following year (Bateson 1906). It was derived directly from the Greek for “birth” (or “origins”).

Straightforward enough. But what about “gene” and “genome”? These terms are interesting because they illustrate the evolution of both concept and language in science and involve both co-option and hybridization.

First, “gene”. Even after the term “genetics” was in use, it was not entirely clear what practitioners of the science were studying. Indeed, the concept of a fundamental physical and functional unit (or “determiner”) of heredity remained very vague. In 1909, Danish biologist Wilhelm Johannsen sought to pin down a term to describe these genetic elements. Although some people attribute the origin of “gene” to the same etymology as “genetics”, there is more to the story. In actuality, “gene” was derived indirectly from Darwin‘s (incorrect) theory of heredity known as “pangenesis“. Indirectly, because it morphed through the term “pangens” coined by the Dutch botanist Hugo de Vries in 1889 in reference to genetic units and as an homage to Darwin, even though his theory of heredity differed markedly from pangenesis (de Vries was a Mendelian).

According to Johannsen (1909, p.143), he came up with the term “gene” by choosing to isolate

the last syllable ‘gene’, which alone is of interest to us, from Darwin’s well known word (Pangenesis) and thereby replace the less desirable ambiguous word ‘determiner’. Consequently, we will speak of ‘the gene’ and ‘the genes’ instead of ‘pangen’ and ‘the pangens’. The word gene is completely free from any hypothesis; it expresses only the evident fact that, in any case, many characteristics of the organism are specified in the germ cells by means of special conditions, foundations, and determiners which are present in unique, separate, and thereby independent ways – in short, precisely what we wish to call genes. [Translation as in Portugal and Cohen 1977].

Johannsen (1909) was also responsible for the terms “genotype” and “phenotype“. As he summarized in 1911,

I have proposed the terms ‘gene’ and ‘genotype’ … to be used in the science of genetics. The ‘gene’ 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 researches. A ‘genotype’ is the sum total of all the ‘genes’ in a gamete or in a zygote.

So, we have an evolution of the term from “pangenesis” (Darwin) to “pangens” (de Vries) to “genes” (Johannsen), passing through an incorrect theory of heredity to a term “completely free from any hypothesis” about inheritance to Mendelian genetics.

What about “genome”?

According to the Oxford English Dictionary, the term “genom(e)” was coined by the German botanist Hans Winkler in 1920 as a portmanteau of gene and chromosome (the latter term having been coined by Wilhelm Waldeyer in 1888). This story has been repeated by many authors (including yours truly; Gregory 2001), but has been challenged by Lederberg and McCray (2001), who suggest that Winkler probably merged gene with the generalized suffix ‘ome (referring to “the entire collectivity of units”), and not ‘some (“body”) from chromosome. In either case, Winkler’s intent was to “propose the expression Genom for the haploid chromosome set, which, together with the pertinent protoplasm, specifies the material foundations of the species” (translation as in Lederberg and McCray 2001).

Based on this initial formulation, “genome” can accurately be taken to mean either the total gene complement (interchangeably with Johannsen’s “genotype”), or the total DNA amount per haploid chromosome set – but not both, as we now know that these are not correlated with one another. This latter issue remains the subject of active study, and I shall have much more to say about it in future postings.

__________

References

Bateson, W. 1906. A text-book of genetics. Nature 74: 146-147.

Bateson, W. 1928. Letter to Sedgwick, April 18, 1905. In William Bateson, F.R.S.: His Essays and Addresses (ed. B. Bateson), pp. 93. Cambridge University Press, Cambridge.

De Vries, H. 1889. Intrazelluläre Pangenesis. Fischer, Jena.

Gregory, T.R. 2001. The bigger the C-value, the larger the cell: genome size and red blood cell size in vertebrates. Blood Cells, Molecules, and Diseases 27: 830-843.

Johannsen, W. 1909. Elemente der Exakten Erblichkeitslehre. Fischer, Jena.

Johannsen, W. 1911. The genotype conception of heredity. American Naturalist 45: 129-159.

Lederberg, J. and A.T. McCray. 2001. ‘Ome sweet ‘omics — a genealogical treasury of words. The Scientist 15: 8.

Portugal, F.H. and J.S. Cohen. 1977. A Century of DNA. MIT Press, Cambridge, MA.

Winkler, H. 1920. Verbeitung und Ursache der Parthenogenesis im Pflanzen und Tierreiche. Verlag Fischer, Jena.



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