History Nature of the Gene

Of the many difficulties facing early genetics, one of the most important was figuring out what a gene was actually made of. As early as 1902, Walter Sutton and Theodore Boveri had observed that, during meiosis, chromosomes separated just as Mendelian particles were proposed to separate. The discovery of sex chromosomes a few years later suggested that chromosomes might play a genetic role, but the association of a specific gene with a chromosome would not occur until 1910, when Thomas Hunt Morgan demonstrated the sex-limited inheritance of the white-eye mutation in Drosophila.

Using the wealth of new information provided by their experiments with Drosophila, Morgan and his colleagues articulated the chromosome theory of inheritance, which treated genes as indivisible particles arranged like beads on a string to form a chromosome. Their patterns of association provided the clues to map their linear order on chromosomes and to understand processes of chromosomal recombination and rearrangement.