The history of genetics can be represented on a timeline of events from the earliest work in the 1850s, to the DNA era starting in the 1940s, and the genomics era beginning in the 1970s.
Early timeline
1856–1863: Mendel studied the inheritance of traits between generations based on experiments involving garden pea plants. He deduced that there is a certain tangible essence that is passed on between generations from both parents. Mendel established the basic principles of inheritance, namely, the principles of dominance, independent assortment, and segregation. 1866: Austrian Augustinian friar Gregor Mendel's paper, Experiments on Plant Hybridization, published. 1869: Friedrich Miescher discovers a weak acid in the nuclei of white blood cells that today we call DNA. In 1871 he isolated cell nuclei, separated the nucleic cells from bandages and then treated them with pepsin (an enzyme which breaks down proteins). From this, he recovered an acidic substance which he called "nuclein".Principles of Genetics / D. Peter Snustad, Michael J. Simmons – 5th Ed. pp.210 1880–1890: Walther Flemming, Eduard Strasburger, and Edouard Van Beneden elucidate chromosome distribution during cell division. 1889: Richard Altmann purified protein free DNA. However, the nucleic acid was not as pure as he had assumed. It was determined later to contain a large amount of protein. 1889: Hugo de Vries postulates that "inheritance of specific traits in organisms comes in particles", naming such particles "(pan)genes".Vries, H. de (1889) Intracellular Pangenesis ("pan-gene" definition on page 7 and 40 of this 1910 translation in English) 1900: Mendelian principles are "rediscovered" and published by 3 botanists independently, Hugo de Vries, Carl Correns and Erich von Tschermak-Seysenegg, setting off a Mendelian revolution 1902: Archibald Garrod discovered inborn errors of metabolism. An explanation for epistasis is an important manifestation of Garrod's research, albeit indirectly. When Garrod studied alkaptonuria, a disorder that makes urine quickly turn black due to the presence of gentisate, he noticed that it was prevalent among populations whose parents were closely related.Principles of Biochemistry / Nelson and Cox – 2005. pp.681Principles of Genetics / D. Peter Snustad, Michael J. Simmons – 5th Ed. pp. 383–384Cell and Molecular Biology, Concepts and experiments / Gerald Karp –5th Ed (2008). pp. 430–431 1903: Walter Sutton and Theodor Boveri independently hypothesizes that chromosomes, which segregate in a Mendelian fashion, are hereditary units; see the chromosome theory. Boveri was studying sea urchins when he found that all the chromosomes in the sea urchins had to be present for proper embryonic development to take place. Sutton's work with grasshoppers showed that chromosomes occur in matched pairs of maternal and paternal chromosomes which separate during meiosis.O'Connor, C. & Miko, I. (2008) Developing the chromosome theory. Nature Education He concluded that this could be "the physical basis of the Mendelian law of heredity." 1905: William Bateson coins the term "genetics" in a letter to Adam SedgwickOnline copy of William Bateson's letter to Adam Sedgwick and at a meeting in 1906. Although the conference was titled "International Conference on Hybridisation and Plant Breeding", Wilks changed the title for publication as a result of Bateson's speech. 1908: G.H. Hardy and Wilhelm Weinberg proposed the Hardy–Weinberg equilibrium model which describes the frequencies of alleles in the gene pool of a population, which are under certain specific conditions, as constant and at a state of equilibrium from generation to generation unless specific disturbing influences are introduced. 1909: Wilhelm Johannsen introduced the term gene. He also coined the terms genotype and phenotype. Johannsen distinguished between an organism's outward appearance (which he designated as its "phenotype") and its inherent genetic heritage (which he designated as its "genotype"). He stressed that an organism's appearance need not correspond exactly to its genetic heritage. So on p. 123 he defines "phenotype": "Darum könnte man den statistisch hervortretenden Typus passend als Erscheinungstypus bezeichnen oder, kurz und klar, als "Phaenotypus". 1) … Ein gebener Phaenotypus mag Ausdruck einer biologischen Einheit sein; er braucht es aber durchaus nicht zu sein. 1) Von φαίν-ομαι, scheinen." (Therefore one could designate the statistically prominent type appropriately as a type of appearance or, clearly and concisely, as a "phenotype". 1) … A given phenotype may be an expression of a biological unit; but it definitely need not be so. 1) From φαίν-ομαι, to appear.) 1910: Thomas Hunt Morgan shows that genes reside on chromosomes while determining the nature of sex-linked traits by studying Drosophila melanogaster. He determined that the white-eyed mutant was sex-linked based on Mendelian's principles of segregation and independent assortment.Principles of Genetics / D. Peter Snustad, Michael J. Simmons – 5th Ed. p.99 1911: Alfred Sturtevant, one of Morgan's collaborators, invented the procedure of linkage mapping which is based on the frequency of crossing-over.Principles of Genetics / D. Peter Snustad, Michael J. Simmons – 5th Ed. pp.147 1913: Alfred Sturtevant makes the first genetic map,Principles of Genetics / D. Peter Snustad, Michael J. Simmons – 5th Ed. pp.109 showing that chromosomes contain linearly arranged genes. 1918: Ronald Fisher publishes "The Correlation Between Relatives on the Supposition of Mendelian Inheritance" the modern synthesis of genetics and evolutionary biology starts. See population genetics. 1920: Lysenkoism Started, during Lysenkoism they stated that the hereditary factor are not only in the nucleus, but also in the cytoplasm, though they called it living protoplasm.Online summary of "Real Genetic vs. Lysenko Controversy 1923: Frederick Griffith studied bacterial transformation and observed that DNA carries genes responsible for pathogenicity.Principles of Genetics / D. Peter Snustad, Michael J. Simmons – 5th Ed. pp.190 1928: Frederick Griffith discovers that hereditary material from dead bacteria can be incorporated into live bacteria. 1930s–1950s: Joachim Hämmerling conducted experiments with Acetabularia in which he began to distinguish the contributions of the nucleus and the cytoplasm substances (later discovered to be DNA and mRNA, respectively) to cell morphogenesis and development. 1931: Crossing over is identified as the cause of recombination; the first cytological demonstration of this crossing over was performed by Barbara McClintock and Harriet Creighton. 1933: Jean Brachet, while studying virgin sea urchin eggs, suggested that DNA is found in cell nucleus and that RNA is present exclusively in the cytoplasm. At the time, "yeast nucleic acid" (RNA) was thought to occur only in plants, while "thymus nucleic acid" (DNA) only in animals. The latter was thought to be a tetramer, with the function of buffering cellular pH.Brachet, J. (1933). Recherches sur la synthese de l'acide thymonucleique pendant le developpement de l'oeuf d'Oursin. Archives de Biologie 44* 519–576.Burian, R. (1994). Jean Brachet's Cytochemical Embryology: Connections with the Renovation of Biology in France? In: Debru, C., Gayon, J. and Picard, J.-F. (eds.). Les sciences biologiques et médicales en France 1920–1950, vol. 2 of Cahiers pour I'histoire de la recherche. Paris: CNRS Editions, pp. 207–220. link . 1933: Thomas Morgan received the Nobel prize for linkage mapping. His work elucidated the role played by the chromosome in heredity. Morgan voluntarily shared the prize money with his key collaborators, Calvin Bridges and Alfred Sturtevant. 1941: Edward Lawrie Tatum and George Wells Beadle show that genes code for proteins; see the original central dogma of genetics. 1943: Luria–Delbrück experiment: this experiment showed that genetic mutations conferring resistance to bacteriophage arise in the absence of selection, rather than being a response to selection.
The DNA era 1944: The Avery–MacLeod–McCarty experiment isolates DNA as the genetic material (at that time called transforming principle).35th anniversary reprint available 1947: Salvador Luria discovers reactivation of irradiated phage, stimulating numerous further studies of DNA repair processes in bacteriophage, and other organisms, including humans. 1948: Barbara McClintock discovers transposons in maize. 1950: Erwin Chargaff determined the pairing method of nitrogenous bases. Chargaff and his team studied the DNA from multiple organisms and found three things (also known as Chargaff's rules). First, the concentration of the pyrimidines (guanine and adenine) are always found in the same amount as one another. Second, the concentration of purines (cytosine and thymine) are also always the same. Lastly, Chargaff and his team found the proportion of pyrimidines and purines correspond each other.Principles of Genetics / D. Peter Snustad, Michael J. Simmons – 5th Ed. pp.217 Table 9.1 1952: The Hershey–Chase experiment proves the genetic information of phages (and, by implication, all other organisms) to be DNA. 1952: an X-ray diffraction image of DNA was taken by Raymond Gosling in May 1952, a student supervised by Rosalind Franklin. 1953: DNA structure is resolved to be a double helix by James Watson, Francis Crick and Maurice Wilkins. 1955: Alexander R. Todd determined the chemical makeup of nitrogenous bases. Todd also successfully synthesized adenosine triphosphate (ATP) and flavin adenine dinucleotide (FAD). He was awarded the Nobel prize in Chemistry in 1957 for his contributions in the scientific knowledge of nucleotides and nucleotide co-enzymes. 1955: Joe Hin Tjio, while working in Albert Levan's lab, determined the number of chromosomes in humans to be of 46. Tjio was attempting to refine an established technique to separate chromosomes onto glass slides by conducting a study of human embryonic lung tissue, when he saw that there were 46 chromosomes rather than 48. This revolutionized the world of cytogenetics. 1957: Arthur Kornberg with Severo Ochoa synthesized DNA in a test tube after discovering the means by which DNA is duplicated. DNA polymerase 1 established requirements for in vitro synthesis of DNA. Kornberg and Ochoa were awarded the Nobel Prize in 1959 for this work.Cell and Molecular Biology, Concepts and experiments / Gerald Karp –5th Ed (2008) pp. 548Principles of Genetics / D. Peter Snustad, Michael J. Simmons – 5th Ed. (Discovery of DNA polymerase I in E. Coli) pp.255 1957/1958: Robert W. Holley, Marshall Nirenberg, Har Gobind Khorana proposed the nucleotide sequence of the tRNA molecule. Francis Crick had proposed the requirement of some kind of adapter molecule and it was soon identified by Holey, Nirenberg and Khorana. These scientists help explain the link between a messenger RNA nucleotide sequence and a polypeptide sequence. In the experiment, they purified tRNAs from yeast cells and were awarded the Nobel prize in 1968.Cell and Molecular Biology, Concepts and experiments / Gerald Karp –5th Ed (2008) pp. 467–469 1958: The Meselson–Stahl experiment demonstrates that DNA is semiconservatively replicated. 1960: Jacob and collaborators discover the operon, a group of genes whose expression is coordinated by an operator.