ABSTRACT
Modern genetics can be seen as the result of the integration of three lines of investigation: statistical analysis of patterns of inheritance; microscopic studies of the intriguing behavior of subcellular entities; and the biochemical researches that elucidated the nature of various cellular components. Classical genetics could address the question of how the gene was transmitted; however, it could not answer the question of how the gene works. Until the mechanism of gene action could be analyzed, geneticists essentially used the gene as a symbol for analyzing Mendelian phenomena. Many geneticists regarded the gene as an abstract concept that was useful in organizing patterns detected by breeding experiments, rather than a material entity. Of course, in the early twentieth century many chemists felt the same way about the atom. But well before the nature of the gene had been clarified, Mendelian-Morganist genetics triumphed over alternative concepts such as soft heredity, cytoplasmic inheritance, and the inheritance of acquired characteristics. A blurring of focus concerning the actual nature of the gene allowed geneticists to think of chromosomal genes and Mendelian factors as if they were known to be the same entity before molecular biology transcended classical genetics and directly attacked the problem of what genes are and how they work.
