1759	Voltaire publishes Candide.
		1760
		1760
		1761
	J. G. Kölreuter carries out crosses between various species of Nicotiana and finds that the hybrids are quantitatively intermediate between their parents in appearance. The hybrids from reciprocal crosses are indistinguishable. He concludes that each parent contributes equally to the characteristics of the offspring.	1761-67
		1762
		1763
		1764
		1765
		1766
		1767
		1768
		1769
		1770
		1770
		1771	The first edition of the Encyclopedia Britannica is published.
		1772
		1773	The "Boston Tea Party" occurs as a protest against British taxation policies.
		1774
		1775	American Revolution begins; British defeated at Lexington.
		1776	Declaration of Independence published.
		1777
		1778
	The peculiar inheritance of human color-blindness reported to The Royal Society of London by M. Lort.	1779
		1780
		1780
		1781	Kant publishes Critique of Pure Reason, a fundamental work of modern philosophy.
		1782
		1783	American Revolution ends; Britain recognizes the independence of the former colonies.
		1784
		1785
		1786
		1787
		1788	Kant publishes Critique of Practical Reason.
		1789	George Washington becomes the first president of the United States.
		1790
		1790	Washington, D.C., founded as the capitol of the United States.
		1791	The first ten amendments to the US Constitution - The Bill of Rights - are ratified.
		1792
		1793
	Erasmus Darwin (Charles' grandfather) publishes Zoonomia, or the Laws of Organic Life.	1794	Slavery abolished in the French colonies.
	James Hutton's Theory of the Earth published, interpreting certain geological strata as former sea beds. Hutton proposes geological theory of gradualism.	1795
		1796	George Washington declines a third term as President, gives his Farewell Address.
		1797	John Adams sworn in as the second president of the United States.
	Publication of Thomas Malthus' Essay on the Principle of Population, a work that Darwin asserted helped him frame the principle of evolution by natural selection.	1798
		1799
		1800
	Karl Friedrich Burdach coins the term BIOLOGY to denote the study of human morphology, physiology and psychology.	1880
		1801	Thomas Jefferson becomes the third president of the United States.
	Gottfried Treviranus and Jean Baptiste de Lamarck independently broaden the meaning of BIOLOGY to include the study of all living things.	1802
		1803	US buys large tract of land from France - The Louisiana Purchase.
		1804
	The field of comparative anatomy begins, with the publications of Baron Georges Cuvier's Lesson in Comparative Anatomy.	1805
		1806
		1807	England prohibits slave trade.
		1808	The US prohibits the importation of new slaves from Africa (but the holding of existing slaves and their descendents remains legal).
	Jean Baptiste de Lamarck's theory of evolution presented with the publication of his Philosophie Zoologique, which emphasized the fundamental unity of life and the capacity of species to vary. Birth of Charles Darwin.	1809	James Madison becomes the fourth president of the United States.
		1810
		1810
		1811	"Luddites" destroy industrial machines in North England, in protest over too rapid modernization.
		1812	US declares war on Britain - War of 1812 begins.
		1813
		1814
		1815
		1816
		1817	James Monroe becomes the fifth president of the United States.
		1818
		1819	Florida purchased by US from Spain. A baby, who would later become Queen Victoria of England, is born carrying a new genetic mutation. Three generations later, that mutation may have changed the course of history.
		1820
	Christian Friedrich Nasse formulated Nasse's law: hemophilia occurs only in males and is passed on by unaffected females.	1820	Debate over slavery in the US heats up; "The Missouri Compromise" admits Maine into the Union as a free state, with Missouri to enter the next year as a slave state.
		1821
		1822
	T. A. Knight, J. Goss, and A. Seton all independently perform crosses with the pea and observe dominance in the immediate progeny, and segregation of various hereditary characters in the next generation. However, they do not study later generations or determine the numerical ratios in which the characters are transmitted.	1822-24
	Thomas Andrew Knight confirmed reports of dominance, recessivity, and segregation in peas, but did not detect regularities.	1823
		1824
		1825	John Quincy Adams becomes the sixth president of the United States.
		1826
	Karl Ernst von Baer first demonstrated the mammalian ovum; he regarded the sperm cells as "Entozoa," i.e., parasites, and named them spermatozoa.	1827
	Publication of Karl Ernst von Baer's The Embryology of Animals which strongly opposed preformationism.	1828
		1829	Andrew Jackson becomes the seventh president of the United States. Slavery abolished in Mexico.
		1830
	Lyell proposes geological theory of uniformitarianism.	1830
	Charles Lyell's multi-volume Principles of Geology appear, advancing the theory of uniformitarianism, i.e., the view that geological formations are explainable in terms of forces and conditions observable at present.	1830-33
	Robert Brown published his observations reporting the discovery and widespread occurrence of nuclei in cells.	1831
	Darwin sails as naturalist aboard the voyage of the HMS Beagle.	1831-36
		1832	Electric telegraph invented by Morse. First horse-drawn public trolleys in New York.
		1833	Charles Babbage designs an analytical engine, the forerunner of modern computers. Abolition of slavery in the British Empire.
		1834
		1835
		1836	Davy Crockett killed at the Alamo.
		1837	Martin Van Buren becomes eighth president of the United States. William IV, King of Great Britain, dies.
	M. J. Schleiden and T. Schwann develop the cell theory. Schleiden notes nucleoli within nuclei. The word PROTEIN first appears in the chemical literature in a paper by G. J. Mulder. The term, however, was invented by J. J. Berzelius.	1838	Victoria coronated as queen of Great Britain.
		1839	The process of vulcanization, developed by Charles goodyear, makes possible the commercial use of rubber.
		1840
	Martin Barry expressed the belief that the spermatozoon enters the egg.	1840
		1841	William Henry Harrison becomes ninth president of the United States; dies one month after inauguration. John Tyler becomes tenth president of the United States.
		1842
	John Stuart Mill publishes Logic.	1843	Congress grants S. F. B. Morse $30,000 to build the first telegraph line (Washington to Baltimore). Sequoyah, Cherokee Indian leader, creates Cherokee syllabary and develops the first written form of a native North American language.
	Darwin first outlines his thoughts on natural selection in an unpublished essay.     Chambers publishes (anonymously) his Vestiges of the Natural History of Creation.	1844
		1845	James K. Polk becomes eleventh president of the United States.
		1846
		1847
		1848
		1849	Zachary Taylor becomes twelfth president of the United States.
		1850
		1850	Millard Fillmore becomes the thirteenth president of the United States, when Zachary Taylor dies in office.
		1851
	Albrecht von Kölliker publishes the first textbook of histology, Handbuch der Gewebelehre.	1852
		1853	Commodore Perry's "black ships" land in Japan. Franklin Pierce becomes fourteenth president of the United States.
		1854
	Alfred Russel Wallace publishes "On the Law which has Regulated the Introduction of New Species," anticipating Darwin's theory of evolution by natural selection. Rudolf Virchow states the principle that new cells come into being only by division of previously existing cells: "Omnis cellula e cellula."	1855
	Gregor Mendel, a monk at the Augustinian monastery of St. Thomas in Brünn, Austria (now Brno, Czechoslovakia), begins breeding experiments with the garden pea, Pisum sativum.	1856
		1857	James Buchanan becomes fifteenth president of the United States.
	Alfred Russel Wallace sends to Darwin a manuscript - "On the Tendency of Varieties to Depart Indefinitely from the Original Type" - that shows clearly that Wallace has independently formulated a model of evolution by natural selection. Darwin's and Wallace's ideas are jointly presented to the Linnaean Society of London.	1858
	Darwin publishes On the Origin of Species.	1859
		1860
		1860
		1861	Abraham Lincoln becomes sixteenth president of the United States. Fort Sumter shelled, American Civil War begins.
		1862
		1863
	Ernst Haeckel (Häckel) outlines the essential elements of modern zoological classification. Louis Pasteur refutes the doctrine of spontaneous generation.	1864	Sherman captures Atlanta, marches to Savannah. Lincoln's reelection destroys South's hope for a political settlement to the war.
	Mendel presents his work on peas to the Brünn Natural History Society. The results are published the following year.	1865	Lee surrenders, US Civil war ends, Lincoln assassinated. Andrew Johnson becomes seventeenth president of the United States.
	Gregor Mendel publishes his findings on heredity in peas, in Versuche über Pflanzen Hybriden. Ernst Heinrich Haeckel (Häckel) hypothesizes that the nucleus of a cell transmits its hereditary information. Ernst Heinrich Haeckel (Häckel) first used the term ECOLOGY to describe the study of living organisms and their interactions with other organisms and with their environment.	1866
		1867
	Darwin publishes Variation in Animals and Plants.	1868	Meiji Restoration in Japan overthrows the feudal shogunate system and initiates Japan's participation in the modern world.
	F. Galton publishes Hereditary Genius. In it he describes a scientific study of human pedigrees from which he concludes that intelligence has a genetic basis.	1869	Ulysses S. Grant becomes eighteenth president of the United States.
		1870
		1870
	Johann Friedrich Miescher isolatesa substance which he calls NUCLEIN from the nuclei of white blood cells that was soluble in alkalis but not in acids. This substance came to be known as nucleic acid. Lambert Adolphe Jacques Quetelet showed the importance of statistical analysis for biologists and laid the foundation of biometry. Publication of Charles Darwin's Descent of Man, in which the role of sexual selection in evolution is described for the first time.	1871
	Ferdinand Julius Cohn coined the term BACTERIUM and founded the study of bacteriology.	1872
	Anton Schneider observed and described the behavior of nuclear filaments (chromosomes) during cell division in his study of the platyhelminth Mesostoma. His account was the first accurate description of the process of mitosis in animal cells.	1873
		1874
	F. Galton demonstrates the usefulness of twin studies for elucidating the relative influence of nature (heredity) and nurture (environment) upon behavioral traits. Oscar Hertwig concludes from a study of the reproduction of the sea urchin that fertilization in both animals and plants consists of the physical union of the two nuclei contributed by the male and female parents. Eduard Strasburger accurately described the processes of mitotic cell division in plants.	1875
		1876	Alexander Graham Bell patents the telephone.
	H. Fol reports watching the spermatozoan of a starfish penetrate the egg. He was able to see the transfer of the intact nucleus of the sperm into the egg, where it became the male pronucleus.	1877	Rutherford B. Hayes becomes nineteenth president of the United States.
	Wilhelm Friedrich Kühne proposed the term ENZYME (meaning "in yeast") and distinguished enzymes from the micro-organisms that produce them.	1878	Edison and Swan produce first successful incandescent electric light.
		1879
	Walther Flemming describes and names CHROMATIN, MITOSIS, and the SPIREME. He makesthe first accurate counts of chromosome numbers and accurately drew the "longitudinal splitting" of chromosomes.	1879-82
		1880
		1880
	Walther Flemming, Eduard Strasburger, Edouard van Beneden, and others elucidated the essential facts of cell division and stressed the importance of the qualitative and quantitative equality of chromosome distribution to daughter cells.	1880-90
		1881	James A Garfield becomes twentieth president of the United States. Six months after taking office, Garfield becomes the second US President to be assassinated. Chester A. Arthur becomes twenty-first president of the United States.
	Eduard Strasburger coins the terms CYTOPLASM and NUCLEOPLASM. W. Flemming discovers lampbrush chromosomes and coins the term MITOSIS.	1882
	Pierre Émile Duclaux introduces the custom of designating an enzyme by the by the name of the substrate on which its action was first reported and adding the suffix "- ase". Edouard van Beneden announced the principles of genetic continuity of chromosomes and reported the occurrence of chromosome reduction at germ cell formation. The sperm and egg are haploid and fertilization restores the diploid chromosome number. Wilhelm Roux offers a possible explanation for the function of mitosis. A. Weismann points out the distinction in animals between the somatic cell line and the germ cells, stressing that only changes in germ cells are transmitted to further generations.	1883
	Walther Flemming, Eduard Strasburger and Edouard van Beneden demonstrate that chromosome doubling occurs by a process of longitudinal splitting. Strasburger describes and names the PROPHASE, METAPHASE, and ANAPHASEstages of chromosomal division.	1884
	Identification of the cell nucleus as the basis for inheritance was independently reported by Oscar Hertwig, Eduard Strasburger, Albrecht von Kölliker, and August Weismann.	1884-88
	Karl Rabl theorized the individuality of chromosomes in all stages of the cell cycle. Walther Flemming observed sister chromatids passing to opposite poles of the cell during mitosis. August Weismann formulated the germ plasm theory which held that the germ plasm was separate from the somatoplasm and was continuous from generation to generation.	1885	Grover Cleveland becomes twenty-second president of the United States.
	Francis Galton devised a new useful statistical tool, the correlation table.	1886	Daimler produces his first car.
	August Weismann elaborated an all-encompassing theory of chromosome behavior during cell division and fertilization and predicted the occurrence of a reduction division (meiosis) in all sexual organisms. Wilhelm Roux put forth the suggestion that the linearly arranged qualities of the chromosomes were equally transmitted to both daughter cells at meiosis. Edouard van Beneden demonstrated chromosome reduction in gamete maturation, thereby confirming August Weismann's predictions.	1887
	Theodor Boveri verifies August Weismann's predictions of chromosome reduction by direct observation in Ascaris. Heinrich Wilhelm Gottfried Waldeyer names the CHROMOSOME.	1888
	Francis Galton publishes Natural Inheritance. In it he describes the quantitative measurement of metric traits in populations. He thus founds biometry and the statistical study of variation. Ultimately, he formulates the Law of Ancestral Inheritance, a statistical description of the relative contributions to heredity made by one's ancestors.	1889	Benjamin Harrison becomes twenty-third president of the United States.
		1890
	The numerical equality of paternal and maternal chromosomes at fertilization was established by Theodor Boveri in Germany and Jean-Louis-Léon Guignard in France.	1890
		1891
	Publication of August Weismann's book Das Keimplasma (The Germ Plasm) emphasized meiosis as an exact mechanism of chromosome distribution.	1892
		1893	Grover Cleveland becomes twenty-fourth president of the United States.
	Hans Dreisch expounded the view that all nuclei of an organism were equipotential but varied in their activity in accordance with the differentiation of tissues. William Bateson's Materials for the Study of Variation emphasized the importance of discontinuous variations, foreshadowing the rediscovery of Mendel's work. Karl Pearson published the first in a long series of contributions to the mathematical theory of evolution. Methods for analyzing statistical frequency distributions were developed in detail.	1894
	Wilhelm Konrad Röntgen (Roentgen) discovered x-rays, which were soon to be applied in the visualization of bodily structures and in the induction of genetic mutations (both intentionally and accidentally).	1895	The Lumiere Brothers introduce moving pictures.
	E. B. Wilson publishes The Cell in Development and Heredity. This influential treatise (ultimately reprinted in several editions) distills the information compliled concerning cytology in the half-century since Schleiden and Schwann put forth the cell theory.	1896
	Gabriel Bertrand coined the term COENZYME to designate inorganic substances which were necessary to activate certain enzymes.	1897	William McKinley becomes twenty-fifth president of the United States.
		1898
	The First International Congress of Genetics held in London. Richard Altmann renamed "nuclein" NUCLEIC ACID. William Bateson writes a paper on hybridisation and cross-breeding as a method of scientific investigation that anticipates Mendel's rediscovery.	1899
		1900
	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.	1900
	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.	1902
	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.
		1904
	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.)	1905
	William Bateson and Reginald Crundall Punnett reported the discovery of two new genetic principles: LINKAGE and GENE INTERACTION.	1906
		1907
	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.	1908
	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.
		1910
	T. H. Morgan discovers white eye and consequently sex linkage in Drosophila. Drosophila genetics begins.	1910
	T. H. Morgan proposes that the genes for white eyes, yellow body, and miniature wings in Drosophila are linked together on the X chromosome.	1911
		1912
	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.	1914
	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.	1915
		1916
	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.	1917
		1918
	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.	1919
		1920
		1920
		1921	Warren Harding becomes twenty-ninth president of the United States.
	L. V. Morgan discovers attached-X chromosomes in Drosophila.	1922
	C. B. Bridges discovers chromosomal translocations in Drosophila. A. E. Boycott and C. Diver describe "delayed" Mendelian inheritance controlling the direction of the coiling of the shell in the snail Limnea peregra. A. H. Sturtevant suggests that the direction of coiling of the Limnea shell is determined by the character of the ooplasm, which is in turn controlled by the mother's genotype.	1923	Harding dies in office. Calvin Coolidge becomes thirtieth president of the United States.
		1924
	A. H. Sturtevant analyzes the Bar-eye phenomenon in Drosophila and discovers position effect.	1925
	A. H. Sturtevant finds the first inversion in Drosophila.	1926
	J. B. S. Haldane suggests that the genes known to control certain coat colors in various rodents and carnivores may be evolutionarily homologous. B. O. Dodge initiates genetic studies on Neurospora. H. J. Muller reports the artificial induction of mutations in Drosophila by x-rays.	1927
	L. J. Stadler reports the artificial induction of mutations in maize, and demonstrates that the dose-frequency curve is linear. F. Griffith discovers type-transformation of pneurnococci. This lays the foundation for the work of Avery, MacLeod, and McCarthy (1944).	1928
		1929	Herbert Hoover becomes thirty-first president of the United States.
		1930
	R. A. Fisher publishes Genetical Theory of Natural Selection, a formal analysis of the mathematics of selection.	1930
	C. Stern, and independently H. B. Creighton and B. McClintock, provide the cytological proof of crossing over.	1931
		1932
	T. S. Painter initiates cytogenetic studies on the salivary gland chromosomes of Drosophila. B. McClintock demonstrates in maize that a single exchange within the inversion loop of a paracentric inversion heterozygote generates an acentric and a dicentric chromatid. T. H. Morgan receives a Nobel Prize in Medicine for his development of the theory of the gene. He is the first geneticist to receive this award.	1933	Franklin D. Roosevelt becomes thirty-second president of the United States.
		1934
	J. B. S. Haldane is the first to calculate the spontaneous mutation frequency of a human gene. G. W. Beadle and B. Ephrussi and A. Kuhn and A. Butenandt work out the biochemical genetics of eye-pigment synthesis in Drosophila and Ephestia, respectively. C. B. Bridges publishes the salivary gland chromosome maps for Drosophila melanogaster.	1935
	A. H. Sturtevant and T. Dobzhansky publish the first account of the use of inversions in constructing a chromosomal phylogenetic tree.	1936
	T. Dobzhansky publishes Genetics and the Origin of Species. A milestone in evolutionary genetics.	1937
		1938
	E. L. Ellis and M. Delbrück perform studies on coliphage growth that mark the beginning of modem phage work. They devise the "one-step growth" experiment, which demonstrates that after the phage adsorbs onto the bacterium, it replicates within the bacterium during the "latent period," and finally the progeny are released in a "burst."	1939
		1940
		1940
	G. W. Beadle and E. L. Tatum publish their classic study on the biochemical genetics of Neurospora and promulgate the ONE-GENE, ONE-ENZYME theory. K. Mather coins the term polygenes and describes polygenic traits in various organisms.	1941
	S. E. Luria and T. F. Anderson publish the first electron micrographs of bacterial viruses. T2 has a polyhedral body and a tail.	1942
	S. E. Luria and M. Delbrück initiate the field of bacterial genetics when they demonstrate unambiguously that bacteria undergo spontaneous mutation.	1943
	O. T. Avery, C. M. MacLeod, and M. McCarty describe the pneumococcus transforming principle. The fact that it is rich in DNA suggests that DNA and not protein is the hereditary chemical.	1944
	S. E. Luria demonstrates that mutations occur in bacterial viruses.	1945	FDR dies in office. Harry S. Truman becomes thirty-third president of the United States.
	J. Lederberg and E. L. Tatum demonstrate genetic recombination in bacteria. Genetic recombination in bacteriophage is demonstrated by M. Delbrück and W. T. Bailey and by A. D. Hershey. Nobel Prize in Medicine awarded to H. J. Muller for his contributions to radiation genetics James B. Sumner, John H. Northrop, and Wendell M. Stanley share a Nobel Prize in Chemistry for Sumner's discovery that enzymes can be crystallized and for Northrop and Stanley's preparation of enzymes and virus proteins in a pure form.	1946
		1947
	H. J. Muller coins the term dosage compensation. J. Lederberg and N. Zinder, and, independently, B. D. Davis develop the penicillin selection technique for isolating biochemically deficient bacterial mutants.	1948
	A. D. Hershey and R. Rotman demonstrate that genetic recombination occurs in bacteriophage. J. V. Neel provides genetic evidence that the sickle-cell disease is inherited as a simple Mendelian autosomal recessive.	1949
		1950
	E. Chargaff lays the foundations for nucleic acid structural studies by his analytical work. He demonstrates for DNA that the numbers of adenine and thymine groups are always equal and so are the numbers of guanine and cytosine groups. These findings later suggest to Watson and Crick that DNA consists of two polynucleotide strands joined by hydrogen bonding between A and T and between G and C. E. M. Lederberg discovers lambda, the first viral episome of E. coli.	1950
		1951
	N. D. Zinder and J. Lederberg describe transduction in Salmonella. J. Lederberg and E. M. Lederberg invent the replica plating technique. F. Sanger and his colleagues work out the complete amino acid sequence for the protein hormone insulin, and show that it contains two polypeptide chains held together by disulfide bridges. A. D. Hershey and M. Chase demonstrate that the DNA of phage enters the host, whereas most of the protein remains behind.	1952
	J. D. Watson and F. H. C. Crick propose a model for DNA comprised of two helically intertwined chains tied together by hydrogen bonds between the purines and pyrimidines. W. Hayes discovers polarized behavior in bacterial recombinations. He isolates the Hfr H strain of E. coli and shows that certain genes are readily transferred from Hfr to F- bacteria, whereas others are not.	1953	Dwight D. Eisnehower becomes thirty-fourth president of the United States.
		1954
	S. Benzer works out the fine structure of the rII region of phage T4 of E. coli, and coins the terms CISTRON,RECON, and MUTON.	1955
	F. Jacob and E. L. Wollman are able experimentally to interrupt the mating process in E. coli and show that a piece of DNA is inserted from the donor bacterium into the recipient.	1956
	V. M. Ingram reports that normal and sickle-cell hemoglobin differ by a single amino acid substitution.	1957
	F. Jacob and E. L. Wollman demonstrate that the single linkage group of E. coli is circular and suggest that the different linkage groups found in different Hfr strains result from the insertion at different points of a factor in the circular linkage group that determines the rupture of the circle. F. H. C. Crick suggests that during protein formation the amino acid is carried to the template by an adaptor molecule containing nucleotides and that the adaptor is the part that actually fits on the RNA template. Crick thus predicts the discovery of transfer RNA. M. Meselson and F. W. Stahl use the density gradient equilibrium centrifugation technique to demonstrate the semiconservative distribution of density label during DNA replication in E. coli. George W. Beadle, Edward L. Tatum, and Joshua Lederberg share a Nobel Prize in Medicine for Beadle and Tatum's discovery that genes act by regulating definite chemical events, and for Lederberg's discoveries concerning genetic recombination and the organization of the genetic material of bacteria. Frederick Sanger receives a a Nobel Prize in Chemistry for his work on the structure of proteins, especially that of insulin.	1958
	J. Lejeune, M. Gautier, and R. Turpin show that Down syndrome is a chromosomal aberration involving trisomy of a small telocentric chromosome. R. L. Sinsheimer demonstrates that bacteriophage phiX174 of E. coli contains a single-stranded DNA molecule. Severo Ochoa and Arthur Kornberg share a Nobel Prize in Medicine for their discovery of the mechanisms in the biological synthesis of ribonucleic acid and deoxiribonucleic acid.	1959
		1960
		1960
	F. Jacob and J. Monod publish "Genetic regulatory mechanisms in the synthesis of proteins," a paper in which the theory of the OPERON is developed.	1961	John F. Kennedy becomes thirty-fifth president of the United States.
	Watson, Crick, and Wilkins share a Nobel Prize in Medicine for their work in elucidating the structure of DNA.	1962
		1963	Kennedy assassinated. Lyndon Johnson becomes thirty-sixth president of the United States.
		1964
	François Jacob, André Lwoff, and Jacques Monod share a Nobel Prize in Medicine for their discoveries concerning genetic control of enzyme and virus synthesis.	1965
		1966
		1967
	Robert W. Holley, Har Gobind Khorana, and Marshall W. Nirenberg share a Nobel Prize in Medicine for their interpretation of the genetic code and its function in protein synthesis.	1968
	Max Delbrück, Alfred D. Hershey, and Salvador E. Luria share a Nobel Prize in Medicine for their discoveries concerning the replication mechanism and the genetic structure of viruses.	1969	Richard M. Nixon becomes thirty-seventh president of the United States.
		1970
		1970
		1971
	Christian B. Anfinsen, Stanford Moore, and William H. Stein share a Nobel Prize in Chemistry, with Anfinsen cited for his work on ribonuclease, especially concerning the connection between the amino acid sequence and the biologically active conformation, and Moore and Stein cited for their contribution to the understanding of the connection between chemical structure and catalytic activity of the active centre of the ribonuclease molecule.	1972
		1973
		1974	Under mounting impeachment pressure resulting from the Watergate breakin, Nixon becomes the first president ever to resign from presidency. Gerald Ford becomes thirty-eighth president of the United States.
	David Baltimore, Renato Dulbecco, and Howard Temin share Nobel Prize in Medicine for their discoveries concerning the interaction between tumour viruses and the genetic material of the cell.	1975
		1976
		1977	Jimmy Carter becomes thirty-ninth president of the United States.
	Werner Arber, Dan Nathans, and Hamilton Smith share a Nobel Prize in Medicine for the discovery of restriction enzymes and their application to problems of molecular genetics.	1978
		1979
		1980
	Paul Berg, Walter Gilbert, and Frederick Sanger share a Nobel Prize in Chemistry, with Berg cited for for his fundamental studies of the biochemistry of nucleic acids, with particular regard to recombinant-DNA, and Gilbert and Sanger cited for their contributions concerning the determination of base sequences in nucleic acids. This is Sanger's second Nobel, the first having come in 1958 for his work on the structure of insulin.	1980
		1981	Ronald Reagan becomes fortieth president of the United States.
		1982
	Barbara McClintock receives the Nobel Prize in Medicine for her discovery of mobile genetic elements.	1983
		1984
		1985
		1986
		1987
		1988
	Sidney Altman and Thomas R. Cech share a Nobel Prize in Chemistry for their discovery of catalytic properties of RNA.	1989	George Bush becomes forty-first president of the United States.
		1990
		1990
		1991
		1992
	Richard J. Roberts, and Phillip A. Sharp share a Nobel Prize in Medicine for for their discoveries of split genes. Kary Mullis and Michael Smith share a Nobel Prize in Chemistry, with Mullis cited for his contributions to the developments of methods within DNA-based chemistry and Smith for his fundamental contributions to the establishment of oligonucleiotide-based, site-directed mutagenesis and its development for protein studies.	1993	William (Bill) Clinton becomes forty-second president of the United States.
		1994
	Edward B. Lewis, Christiane Nüsslein-Volhard, and Eric F. Wieschaus share a Nobel Prize in Medicine for for their discoveries concerning the genetic control of early embryonic development.	1995
		1996
		1997
		1998
		1999
		2000