Historical Development Of Molecular Cytogenetics

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Molecular cytogenetics involves the combination of molecular biology and cytogenetics. In general this involves the use of a series of techniques referred to as fluorescence in situ hybridization in which DNA probes are labeled with different colored fluorescent tags to visualize one or more specific regions of the genome. Alternatively, an indirect approach can be taken in which the entire genome can be assessed for copy number changes using virtual karyotyping.

Virtual karyotypes are generated from arrays made of thousands to millions of probes and computational tools are used to recreate the genome in silico. The concept of biology arose in the 19th century; the biological sciences emerged from traditions of medicine and natural history reaching back to ayurveda, ancient Egyptian medicine and the works of Aristotle and Galen in the ancient Greco-Roman world. This ancient work was further developed in the middle age by Muslim physicians and scholars such as Avicenna. During the European Renaissance and early modern period, biological thought was revolutionized in Europe by a renewed interest in empiricism and the discovery of many novel organisms. Prominent in this movement were Vesalius and Harvey, who used experimentation and careful observation in physiology and naturalists such as Linnaeus and Buffon who began to classify the diversity of life and the fossil record, as well as the development and behavior of organisms. Microscopy revealed the previously unknown world of microorganisms, laying the groundwork for cell theory. The growing importance of natural theology, partly a response to the rise of mechanical philosophy, encouraged the growth of natural history.

Over the 18th and 19th centuries, biological sciences such as botany and zoology became increasingly professional scientific disciplines. Lavoisier and other physical scientists began to connect the animate and inanimate worlds through physics and chemistry. Explorer-naturalists such as Alexander von Humboldt investigated the interaction between organisms and their environment and the ways this relationship depends on geography, laying the foundations for biogeography, ecology and ethology. Naturalists began to reject essentialism and consider the importance of extinction and the mutability of species. Cell theory provided a new perspective on the fundamental basis of life. These developments, as well as the results from embryology and paleontology, were synthesized in Charles Darwin's theory of evolution by natural selection. The end of the 19th century saw the fall of spontaneous generation and the rise of the germ theory of disease, though the mechanism of inheritance remained a mystery. In the early 20th century, the rediscovery of Mendel's work led to the rapid development of genetics by Thomas Hunt Morgan and his students and by the 1930s the combination of population genetics and natural selection in the neo-Darwinian synthesis. New disciplines developed rapidly, especially after Watson and Crick proposed the structure of DNA. Following the establishment of the Central Dogma and the cracking of the genetic code, biology was largely split between organismal biology the fields that deal with whole organisms and groups of organisms and the fields related to cellular and molecular biology. By the late 20th century, new fields like genomics and proteomics were reversing this trend, with organismal biologists using molecular techniques and molecular and cell biologists investigating the interplay between genes and the environment, as well as the genetics of natural populations of organisms. Here is the historical development (year wise) of molecular cytotgenetics as follows:

1865: Gregor Mendel's paper, Experiments on Plant Hybridization

1869: Friedrich Miescher discovers a weak acid in the nuclei of white blood cells that today we call DNA

1880-1890: Walther Flemming, Eduard Strasburger and Edouard van Beneden elucidate chromosome distribution during cell division

1889: Hugo de Vries postulates that inheritance of specific traits in organisms comes in particles, naming such particles (pan) genes

1903: Walter Sutton hypothesizes that chromosomes, which segregate in a Mendelian fashion, are hereditary units

1905: William Bateson coins the term genetics in a letter to Adam Sedgwick and at a meeting in 1906

1908: Hardy-Weinberg law derived.

1910: Thomas Hunt Morgan shows that genes reside on chromosomes

1913: Alfred Sturtevant makes the first genetic map of a chromosome

1913: Gene maps show chromosomes containing linear 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.

1928: Frederick Griffith discovers that hereditary material from dead bacteria can be incorporated into live bacteria

1931: Crossing over is identified as the cause of recombination

1933: Jean Brachet is able to show that DNA is found in chromosomes and that RNA is present in the cytoplasm of all cells.

1941: Edward Lawrie Tatum and George Wells Beadle show that genes code for proteins

1944: The Avery, MacLeod, McCarty experiment isolates DNA as the genetic material

1948: Barbara McClintock discovers transposons in maize

1950: Erwin Chargaff shows that the four nucleotides are not present in nucleic acids in stable proportions, but that some general rules appear to hold e.g., that the amount of adenine A, tends to be equal to that of thymine T.

1952: The Hershey-Chase experiment proves the genetic information of phages  to be DNA

1953: DNA structure is resolved to be a double helix by James D. Watson and Francis Crick

1956: Joe Hin Tjio and Albert Levan established the correct chromosome number in humans to be 46

1958: The Meselson-Stahl experiment demonstrates that DNA is semiconservatively replicated

1961-1967: Combined efforts of scientists crack the genetic code, including Marshall Nirenberg, Har Gobind Khorana, Sydney Brenner and Francis Crick

1964: Howard Temin showed using RNA viruses that the direction of DNA to RNA transcription can be reversed

1970: Restriction enzymes were discovered in studies of a bacterium, Haemophilus influenzae, enabling scientists to cut and paste DNA

1972: Walter Fiers and his team at the Laboratory of Molecular Biology of the University of Ghent (Belgium) were the first to determine the sequence of a gene: the gene for bacteriophage MS2 coat protein.

1976: Walter Fiers and his team determine the complete nucleotide-sequence of bacteriophage MS2-RNA

1977: DNA is sequenced for the first time by Fred Sanger, Walter Gilbert and Allan Maxam working independently. Sanger's lab sequence the entire genome of bacteriophage Φ-X174.

1983: Kary Banks Mullis discovers the polymerase chain reaction enabling the easy amplification of DNA

1989: The human gene that encodes the CFTR protein was sequenced by Francis Collins and Lap-Chee Tsui. Defects in this gene cause cystic fibrosis.

1995: The genome of Haemophilus influenzae is the first genome of a free living organism to be sequenced

1996: Saccharomyces cerevisiae is the first eukaryote genome sequence to be released

1998: The first genome sequence for a multicellular eukaryote, Caenorhabditis elegans, is released

2000: Starlink Bt corn, manufactured by Aventis Crop Science and supposedly produced only for livestock feed, is found in taco shells in the United States, to which some people claim to have had an allergic reaction. Starlink corn is subsequently discontinued, although no adverse health reactions are proven.

2001: First draft sequences of the human genome are released simultaneously by the Human Genome Project and Celera Genomics.

-The President’s Council on Bioethics is established by George W. Bush.

-Germany establishes the Bio-Seigel, a seal of approval granted to certified organic products.

-Scientists at the University of Guelph in Canada trademark the Enviropig; it is genetically engineered to produce low-phosphorus manure, which will result in less soil and water pollution.

2002: Japan’s Biotechnology Strategy Council drafts the Biotechnology Strategy Guidelines, intended to guide the economic development of the life sciences in the country in the 21st century.

-Bayer CropScience is spun off from Bayer USA, a division of the German based pharmaceutical conglomerate Bayer.

2003 (14 April): Successful completion of Human Genome Project with 99% of the genome sequenced to a 99.99% accuracy

On May 13, the U.S. government files a challenge with the World Trade Organization stating that the European Union’s anti-GM food policy violates international agreements.

On September 11, the Cartagena Protocol on Biosafety enters into force (on GMO), with the goal of protecting existing biodiversity from organisms modified through modern biotechnology.

On November 27, the Icelandic Supreme Court bars the implementation of the Icelandic Health Sector Database which contains tissue of and genetic information on Iceland’s 300,000 citizens by the biotech company deCODE

2004: In Monsanto Canada Inc. v. Schmeiser, the Supreme Court of Canada rules in favor of Monsanto, stating that Saskatchewan farmer Percy Schmeiser deprived Monsanto of its monopoly on its proprietary GM canola seed by inadvertently and unknowingly storing and planting Roundup Ready canola seeds in his fields.

2005: The United Nations General Assembly approves the Declaration on Human Cloning, a nonbinding resolution that calls for a ban on all forms of reproductive and therapeutic cloning.

-The United States and Germany both vote in favor of the ban, but countries such as Great Britain, which have a significant industry in stem cell research, vote against it.

2007: On September 4, Celera Genomics publishes the complete human genome, consisting of a sequence of 6 billion nucleotides of the company’s founder, Craig Venter.

In November, two researchers, James Thomson of University of Wisconsin–Madison and Yamanaka Shinya at Kyoto University in Japan, announce independently that they have created induced pluripotent stem cells (iPSC), which are stem cells created from human skin cells that can be used to create any kind of cell without destroying an embryo.

2008: Stemagen scientists Andrew French and Samuel Wood announce that they have cloned several human embryos from adult skin cells using the somatic cell nuclear transfer technique. The embryos are later destroyed.

On May 21, the Genetic Information Nondiscrimination Act of 2007 is signed into law by President George W. Bush, which prohibits the improper use of genetic information by health insurers and employers.

-India’s Prime Minister Manmohan Singh calls for a second Green Revolution in the country, which will use agricultural biotechnology to drastically expand the country’s crop yields and eliminate hunger.

2009: In March, President Obama reverses George W. Bush’s policy on stem cell research, allowing hundreds of new embryonic stem cell lines to be used in federally funded research.


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