Nature of the Gene, History
Although Wilhelm Johannsen coined the term "gene" in 1909, our understanding of the nature of the gene has changed significantly over the course of the twentieth century. Gregor Mendel's elements of inheritance were given a material basis in the chromosome theory of the early twentieth century. Attempts to understand the nature of gene action and mutation spurred interest in the biochemical role and molecular basis of the gene, culminating in the discovery of the structure of DNA.
From Elements to Genes
In 1865, when Mendel articulated the laws of inheritance that now bear his name, he did not use the terms "gene" or " allele." He referred instead to "elements" and "characters." Mendel described the patterns of inheritance he observed in terms of character pairs. These pairs segregate to form the next generation of character pairs and remain independent of the behavior of other character pairs. The external characters of the pea plants he described corresponded to elements within the germ cells of the same plants. Whether Mendel thought that pairs of characters were expressions of pairs of cellular elements is not clear.
By the time of Mendel's rediscovery in 1900 by Hugo de Vries, Carl Correns, and Erich Tschermak, however, visible characters were understood to be expressions of hereditary particles within each cell.
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