| Cloning Timeline |
| 1885 | August Weismann, professor of zoology and comparative anatomy at the University of Freiberg, theorized that the genetic information of a cell would diminish as the cell went through differentiation. |
| 1888 | Wilhelm Roux tested the germ plasm theory for the first time. One cell of a 2-cell frog embryo was destroyed with a hot needle; the result was a half-embryo, supporting Weismann's theory. |
| 1894 | Hans Dreisch isolated blastomeres from 2- and 4-cell sea urchin embryos and observed their development into small larvae. These experiments were regarded as refutations of the Weismann-Roux theory. |
| 1901 | Hans Spemann split a 2-cell newt embryo into two parts, resulting in the development of two complete larvae. |
| 1902 | Walter Sutton published "On the Morphology of the Chromosome Group in Brachyotola magna", hypothesizing that chromosomes carry the inheritance and that they occur in distinct pairs within a cell's nucleus. Sutton also argued that how chromosomes act when sex cells divide was the basis for the Mendelian Law of Heredity. |
| 1902 | German embryologist Hans Spemann split a 2-celled salamander embryo and each cell grew to adulthood, providing proof that early embryo cells carry necessary genetic information. This finally disproved Weismann's 1885 theory that the amount of genetic information in cells decreases with each division. |
| 1914 | Hans Spermann conducted and early nuclear transfer experiment. |
| 1928 | Hans Spemann performed further, successful nuclear transfer experiments. |
| 1938 | Hans Spemann published the results of his 1928 primitive nuclear transfer experiments involving salamander embryos in the book "Embryonic Development and Induction." Spemann argued the next step for research should be the cloning organisms by extracting the nucleus of a differentiated cell and putting it into an enucleated egg. |
| 1944 | Oswald Avery found that a cell's genetic information was carried in DNA. |
| 1950 | First successful freezing of bull semen at -79°C for later insemination of cows was accomplished. |
| 1952 | First animal cloning: Robert Briggs and Thomas J. King cloned northern leopard frogs. |
| 1953 | Francis Crick and James Watson ,working at Cambridge's Cavendish Laboratory, discovered the structure of DNA. |
| 1962 | Biologist John Gurdon announced that he had cloned South African frogs using the nucleus of fully differentiated adult intestinal cells. This demonstrated that cells' genetic potential do not diminish as the cell became specialized. |
| 1962 - 65 | Robert G. McKinnell, Thomas J. King, and Marie A. Di Berardino produced swimming larvae from enucleated oocytes that had been injected with adult frog kidney carcinoma cell nuclei. |
| 1963 | Biologist J.B.S. Haldane coined the term "clone" in a speech entitled "Biological Possibilities for the Human Species of the Next Ten-Thousand Years." |
| 1964 | F.C. Steward grew a complete carrot plant from a fully differentiated carrot root cell. |
| 1966 | Marshall Niremberg, Heinrich Mathaei, and Severo Ochoa broke the genetic code, discovering what codon sequences specified each of the twenty amino acids. |
| 1966 | John B. Gurdon and V. Uehlinger grew adult frogs after injecting tadpole intestinal cell nuclei into enucleated oocytes. |
| 1967 | DNA ligase, the enzyme responsible for binding together strands of DNA, was isolated. |
| 1969 | James Shapiero and Johnathan Beckwith announced that they had isolated the first gene. |
| 1970 | Howard Temin and David Baltimore each independently isolated the first restriction enzyme. |
| 1972 | Paul Berg combined the DNA of two different organisms, thus creating the first recombinant DNA molecules. |
| 1973 | Stanley Cohen and Herbert Boyer created the first recombinant DNA organism using recombinant DNA techniques pioneered by Paul Berg. Also known as gene splicing, this technique that allows scientists to manipulate the DNA of an organism - the basis of genetic engineering. |
| 1977 | Karl Illmensee and Peter Hoppe created mice with only a single parent. |
| 1978 | David Rorvik published the novel In His Image: The Cloning of a Man. |
| 1978 | Baby Louise, the first child conceived through in vitro fertilization, was born. |
| 1979 | Karl Illmensee claimed to have cloned three mice. |
| 1980 | In the case Diamond v. Chakrabarty, the United States Supreme Court ruled that a "live, human made microorganism is patentable material." |
| 1983 | Kary B. Mullis developed the polymerase chain reaction (PCR) in 1983. This process allows for the rapid synthesis of designated fragments of DNA. |
| 1983 | Davor Solter and David McGrath tried to clone mice using their own version of the nuclear transfer method. |
| 1983 | The first human mother-to-mother embryo transfer was completed. |
| 1983 - 86 | Marie A. Di Berardino, Nancy H. Orr, and Robert McKinnell transplanted nuclei of adult frog erythrocytes, thus obtained pre-feeding and feeding tadpoles. |
| 1984 | Steen Willadsen cloned a sheep from embryo cells, the first verified example of mammal cloning using the process of nuclear transfer. |
| 1985 | Steen Willadsen used his cloning technique to duplicate prize cattle embryos. |
| 1985 | Ralph Brinster created the first transgenic livestock: pigs that produced human growth hormone. |
| 1986 | Using differentiated, one week old embryo cells, Steen Willadsen cloned a cow. |
| 1986 | Artificially inseminated surrogate mother Mary Beth Whitehead gave birth to Baby M. She tried and failed to retain custody. |
| 1986 | Neal First, Randal Prather, and Willard Eyestone used early embryo cells to clone a cow. |
| October 1990 | The National Institutes of Health officially launched the Human Genome Project to locate the 50,000 to 100,000 genes and sequence the estimated 3 billion nucleotides of the human genome. |
| 1993 | M. Sims and N.L. First reported the creation of calves by transfer of nuclei from cultured embryonic cells. |
| 1993 | Human embryos were first cloned. |
| July 1995 | Ian Wilmut and Keith Campbell used differentiated embryo cells to clone two sheep, named Megan and Morag. |
| July 5, 1996 | Dolly, the first organism ever to be cloned from adult cells, was born. |
| February 23, 1997 | Scientists at the Roslin Institute in Scotland officially announced the birth of "Dolly" |
| March 4, 1997 | President Clinton proposed a five year moratorium on federal and privately funded human cloning research. |
| July 1997 | Ian Wilmut and Keith Campbell, the scientists who created Dolly, also created Polly, a Poll Dorset lamb cloned from skin cells grown in a lab and genetically altered to contain a human gene. |
| August 1997 | President Clinton proposed legislation to ban the cloning of humans for at least 5 years. |
| September 1997 | Thousands of biologists and physicians signed a voluntary five-year moratorium on human cloning in the United States. |
| December 5, 1997 | Richard Seed announced that he intended to clone a human before federal laws could effectively prohibit the process. |
| early January 1998 | Nineteen European nations signed a ban on human cloning. |
| January 20, 1998 | The Food and Drug Administration announced that it had authority over human cloning. |
| July 1998 | Ryuzo Yanagimachi, Toni Perry, and Teruhiko Wakayama announced that they had cloned 50 mice from adult cells since October, 1997. |
| January 1998 | Botechnology firm Perkin-Elmer Corporation announced that it wold work with gene sequencing expert J. Craig Venture to privately map the human genome. |
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