T. H. Morgan discovers white eye and consequently sex linkage in Drosophila. Drosophila genetics begins.
  T. H. Morgan proposes that the genes for white eyes, yellow body, and miniature wings in Drosophila are linked together on the X chromosome.
  A. H. Sturtevant, an undergraduate working with Morgan at Columbia, provides the experimental basis for the linkage concept in Drosophila and produces the first GENETIC MAP.
1913 Woodrow Wilson becomes twenty-eighth president of the United States.
  Calvin Blackman Bridges reports nondisjunction of sex chromosomes as a proof of the chromosome theory of heredity.
  The Mechanism of Mendelian Heredity, an epochal book, published by Thomas Hunt Morgan, Alfred Henry Sturtevant, Calvin Blackman Bridges, and Hermann Joseph Muller.

Frederick Twort discovered a virus capable of infecting and destroying bacteria.

  Felix Hubert D'Herelle, independently of Frederick Twort, discovers a virus capable of infecting and destroying bacteria, which he calls a BACTERIOPHAGE.

C. B. Bridges discovers the first chromosome deficiency in Drosophila.

  Thomas Hunt Morgan and coworkers published The Physical Basis of Heredity, a book-length summary of the rapidly growing findings in genetics.

T. H. Morgan calls attention to the equality in Drosophila melanogaster between the number of linkage groups and the haploid number of chromosomes.

C. B. Bridges discovers chromosomal duplications in Drosophila.