H. de Vries, C. Correns, and E. Tschermak independently rediscover Mendel's paper. Using several plant species, de Vries and Correns had performed breeding experiments that paralleled Mendel's earlier studies and had independently arrived at similar interpretations of their results. Therefore, upon reading Mendel's publication they immediately recognized its significance. W. Bateson also stresses the importance of Mendel's contribution in an address to the Royal Society of London.

K. Pearson develops the chi-square test.

K. Landsteiner discovers the blood-agglutination phenomenon in man.

  H. de Vries adopts the term MUTATION to describe sudden, spontaneous, drastic alterations in the hereditary material of Oenothera.

T. H. Montgomery studies spermatogenesis in various species of Hemiptera. He concludes that maternal chromosomes only pair with paternal chromosomes during meiosis.

1901 Theodore Roosevelt becomes twenty-sixth president of the United States.
  C. E. McClung argues that particular chromosomes determine the sex of the individual carrying them, not just in insects, but perhaps in other species (including man)..

Walter Sutton concludes that (a) chromosomes have individuality, (b) that they occur in pairs, with one member of each pair contributed by each parent, and (c) that the paired chromosomes separate from each other during meiosis.

T. Boveri studies sea urchin embryos and finds that in order to develop normally, the organism must have a full set of chromosomes, and from this he concludes that the individual chromosomes must carry different essential hereditary determinants.

Archibald Garrod, a British physician, reports that a human disease, alkaptonuria, seems to be inherited as a Mendelian recessive.

William Bateson coins the terms GENETICS, F1, F2, ALLELOMORPH (later shortened to ALLELE), HOMOZYGOTE, HETEROZYGOTE, and EPISTASIS.

  The concepts of PHENOTYPE, GENOTYPE, and SELECTION were introduced and clearly defined by Wilhelm Ludwig Johannsen.

Carl Neuberg first used the term BIOCHEMISTRY.

1903 Orville and Wilbur Wright succeed with the first controlled flight in a heavier-than-air machine.
  Lucien Claude Cuénot performs crosses between mice carrying a gene that gives them yellow fur. Since they always produce yellow furred and agouti offspring in a 2:1 ratio, he concludes they are heterozygous. (W. E. Castle and C. C. Little show in 1910 that yellow homozygotes die in utero. This dominant allele in the agouti series (AY) is thus the first gene shown to behave as a homozygous lethal.)
  William Bateson and Reginald Crundall Punnett reported the discovery of two new genetic principles: LINKAGE and GENE INTERACTION.
  Godfrey Harold Hardy, a Cambridge mathematician, writes a letter to the editor of Science, suggesting that Mendelian mechanisms acting alone have no effect on allele frequencies. This observation forms the mathematical basis for population genetics.
  T. H. Morgan, later to become the first recipient of the Nobel Prize for work in genetics, writes a paper expressing doubts about the profusion of Mendelian explanations for inherited properties.

G. H. Shull advocates the use of self-fertilized lines in production of commercial seed corn. The hybrid corn program that resulted, created an abundance of foodstuffs worth billions of dollars.

A. E. Garrod publishes Inborn Errors of Metabolism, the earliest discussion of the biochemical genetics of man (or any other species).

W. Johannsen's studies of the inheritance of seed size in self-fertilized lines of beans leads him to realize the necessity of distinguishing between the appearance of an organism and its genetic constitution. He invents the terms PHENOTYOPE and GENOTYPE to serve this purpose, and he also coins the word GENE.

H. Nilsson Ehle puts forward the multiple-factor hypothesis to explain the quantitative inheritance of seed-coat color in wheat.

1909 William Howard Taft becomes twenty-seventh president of the United States.

Ford begins mass-producing Model T.