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Darwin’s understanding of genetics and hereditary concepts appear in his writing, introducing the term “survival of the fittest.”
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George Mendel describes his experiments with peas, showing that heredity is transmitted in discrete units
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Friedrich Miescher isolates DNA for the first time when working with white blood cells.
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Walter Flemming describes chromosome behavior during animal cell division.
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DeVries, Correns, and Tschermak rediscover and bring awareness to the Mendelian laws of inheritance
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Walter Sutton, a graduate student in E. B. Wilson's lab at Columbia University, observed that in the process of cell division, called meiosis, that produces sperm and egg cells, each sperm or egg receives only one chromosome of each type.
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Archibald Garrod observes that the disease alkaptonuria is inherited according to Mendelian rules.
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Danish botanist Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity.He also made the distinction between the outward appearance of an individual (phenotype) and its genetic traits (genotype).
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Using fruit flies as a model organism, Thomas Hunt Morgan and his group at Columbia University showed that genes, strung on chromosomes, are the units of heredity.
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George Beadle and Edward Tatum, through experiments on the red bread mold Neurospora crassa, showed that genes act by regulating distinct chemical events - affirming the "one gene, one enzyme" hypothesis
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William Astbury, a British scientist, obtained the first X-ray diffraction pattern of DNA.
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Oswald Avery, Colin MacLeod, and Maclyn McCarty showed that DNA (not proteins) can transform the properties of cells, clarifying the chemical nature of genes.
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Barbara McClintock discovers that genes can jump around on chromosomes, showing that the genome is more dynamic than previously thought.
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Alfred Hershey and Martha Chase showed that only the DNA of a virus needs to enter a bacterium to infect it.
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Francis Crick and James Watson described the double helix structure of DNA based on images taken by Rosalind Franklin
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Joe Hin Tjio defined 46 as the exact number of human chromosomes.
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Arthur Kornberg and his colleagues isolated DNA polymerase, an enzyme later used for all kinds of recombinant DNA techniques and for sequencing.
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Sickle cell anemia was first described in 1910, after Ernest E. Irons, an intern at Chicago's Presbyterian Hospital, noticed elongated cells in a blood smear from Walter C. Noel, a dental student with severe anemia.
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Matthew Meselson and Franklin Stahl demonstrated that DNA replicates semiconservatively, with each strand in a DNA molecule from the parent generation pairing with a new strand in the daughter generation
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Professor Jerome Lejeune and his colleagues discovered that Down syndrome, first classified by J. L. H. Down in 1866, is caused by trisomy 21 - that is, having three instead of 2 copies of chromosome 21.
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Sydney Brenner, Francois Jacob, and Matthew Meselson discovered that mRNA is the molecule that takes information from DNA in the nucleus to the protein-making machinery in the cytoplasm.
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Robert Guthrie, a doctor and bacterial scientist at the University of Buffalo Children's Hospital, developed a way to test whether newborn babies have phenylketonuria (PKU), an inability to digest the amino acid phenylalanine.
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Over the course of several years, Marshall Nirenberg, Har Khorana and Severo Ochoa and their colleagues elucidated the genetic code - showing how nucleic acids with their 4-letter alphabet determine the order of the 20 kinds of amino acids in proteins.
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Several groups of researchers - including M. Meselson's group at Harvard and H. O. Smith, K. W. Wilcox, and T. J. Kelley at Johns Hopkins - studied and characterized the first restriction nucleases, enzymes that revolutionized molecular biologists' ability to manipulate DNA.
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The first production of recombinant DNA molecules, using restriction enzymes, occurred in the early 1970s.
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Stanford and UCSF researchers fused a segment of DNA containing a gene from the African clawed frog Xenopus with DNA from the bacterium E. coli and placed the resulting DNA back into an E. coli cell.
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The first genetic engineering company, Genentech, was founded in 1976.
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Sanger and his colleagues, and Maxam and Gilbert developed rapid DNA sequencing methods.
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Richard Roberts' and Phil Sharp's labs showed that eukaryotic genes contain many interruptions, called introns.
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Scientists had been able to add new genes to bacterial cells for several years. In the early 1980s, they figured out how to add stably-inherited new genes to animals.
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GenBank, NIH's publicly accessible genetic sequence database, was formed at Los Alamos National Laboratory.
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A genetic marker linked to Huntington disease was found on chromosome 4 in 1983, making Huntington disease, or HD, the first genetic disease mapped using DNA polymorphisms.
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PCR - the polymerase chain reaction - is a technique for amplifying DNA that dramatically boosted the pace of genetic research.
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Positional cloning is the method of finding a gene without any knowledge of the protein it encodes. The first human disease gene identified by positional cloning was one for chronic granulomatous disease.
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The first comprehensive genetic map of human chromosomes was based on 400 restriction fragment length polymorphisms (RFLPs), which are variations in DNA sequence that can be observed by digesting DNA with restriction enzymes.
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Yeast artificial chromosomes (YAC) can carry large segments of DNA from other species, like humans.
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A microsatellite is a stretch of DNA made of a two to four base-pair long sequence that is repeated in tandem - e.g. a stretch of DNA that looks like this: CAGCAGCAGCAGCAGCAGCAG.
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A sequence-tagged site (STS) is a unique stretch of DNA that polymerase chain reaction (PCR) can easily detect.
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The Human Genome Project officialy began in 1990. Beginning in December 1984, the U.S. Department of Energy (DOE), National Institutes of Health (NIH) and international groups had sponsored meetings to consider the feasibility and usefulness of mapping and sequencing the human genome.
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Ethical, Legal and Social Implications (ELSI) programs founded at NIH and DOE.
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In 1990, researchers began to study how to efficiently produce stable carriers of large DNA inserts in bacteria, so-called BACs.
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An expressed-sequence tag (EST) is a stretch of DNA sequence made by copying a portion of an mRNA molecule.
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A team from France built a low-resolution, microsatellite genetic map of the entire human genome.
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The DOE and NIH set up an agreement on how to share resources and release data to the community of researchers.
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Unexpectedly rapid progress toward the goals established in 1990 led the National Institutes of Health and the Department of Energy to establish a new set of goals for the Human Genome Project in 1993, two years ahead of schedule.
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The FDA approved the sale of the first genetically modified food - the FLAVR SAVR tomato, deeming it as safe as conventionally-bred tomatoes.
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One of the primary goals of the Human Genome Project's 1993 five-year plan was to complete a detailed genetic map of the human genome by 1995. Genetic mapping was a critical early step in the hunt for disease genes - allowing researchers to find on which chromosome a gene lies and approximately where in that chromosome. Researchers completed the genetic mapping goal one year ahead of schedule, and the map was denser (had more markers) than originally proposed.
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The DOE began a Microbial Genome Program in late 1994 to sequence the genomes of some bacteria.
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The U.S. Equal Employment Opportunity Commission extended workplace protections under the Americans with Disabilities Act to cover discrimination based on genetic information.
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A physical map uses sequence-tagged sites (STSs) as markers to order large segments of DNA. The map built by 1995 was a significant milestone toward that goal; it contained 15,086 STSs, spaced an average of 199,000 base pairs apart.
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The first international strategy meeting on human genome sequencing drew scientists from the countries in Europe, North America, and Asia funding human genome sequencing projects.
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Scientists created a map showing the locations of ESTs (expressed sequence tags) representing fragments of more than 16,000 genes from throughout the genome.
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In 1996, the National Human Genome Research Institute funded pilot projects to find efficient strategies for completely sequencing the human genome.
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A Task Force on Genetic Testing was created by the NIH-DOE Working Group on Ethical, Legal, and Social Implications of Human Genome Research to review genetic testing in the United States and make recommendations to ensure the development of safe and effective genetic tests
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In October 1998, HGP researchers released a gene map that included 30,000 human genes, estimated to represent approximately one-third of the total human genes.
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In December 1998, the first genome sequence of a multicellular organism, the roundworm Caenorhabditis elegans, was completed.
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In March 1999, HGP participants advanced their goal of obtaining draft sequence covering 90 percent of the human genome to 2000, a year and a half before projected previously.
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In December 1999, the HGP completed the first finished, full-length sequence of a human chromosome - chromosome 22. This accomplishment demonstrated the power of the HGP method of clone-by-clone sequencing to obtain large amounts of highly accurate sequence.
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In March 2000, U.S. President Clinton and U.K. Prime Minister Tony Blair stated that raw, fundamental data about human genome sequence and its variations should be freely available.
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The Human Genome Project international consortium published a first draft and initial analysis of the human genome sequence. The draft sequence covered more than 90 percent of the human genome.
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Researchers identified a gene on chromosome 1 associated with a hereditary form of prostate cancer.
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The International Human Genome Sequencing Consortium announced the successful completion of the Human Genome Project more than two years ahead of schedule and under budget.
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In April 1953, a paper appeared in the journal Nature that proposed a double helix structure for deoxyribose nucleic acid DNA.
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The United States Congress passed a resolution setting aside April 25th as National DNA Day.