Category:Clinical genetics

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Contents

Introduction

What is Clinical genetics?

Clinical genetics is the specialty which provides a diagnostic service and "genetic counselling" for individuals or families with, or at risk of, conditions which may have a genetic basis. It will evolve to support gene therapy. Genetic disorders can affect any body system and any age group. The aim of genetic services is to help those affected by, or at risk of, a genetic disorder to live and reproduce as normally as possible. Genetic disorders include :

  • Chromosomal abnormalities, which cause birth defects, mental retardation and/or reproductive problems.

In addition a large number of individuals with birth defects and/or learning disabilities are referred and investigated for genetic factors. Individuals identified through childhood or pregnancy screening programmes also require genetic services. In the future, as the genetic contributions to common later-onset disorders such as diabetes and coronary heart disease are identified, genetic services may be required for those at high risk.

Historical

  • 15000 BC Domestication of dogs. Hereditary traits of the offspring assumed to be the diluted or strengthening by blending of whatever traits were present in the parents. Also commonly assuned that, over generations, a hybrid would revert to its original form, the implication of which suggested that a hybrid could not create new forms.
  • 1831 Robert Brown described the areola (nucleus) in orchids being constantly detectable in all cells.
  • 1842 Karl Wilhelm von Nägeli first described subcellular structures known latter as chromosomes.
  • 1854 Gregor Mendel began to research the transmission of hereditary traits in plant hybrids
  • 1865 Mendel's two lectures to the Natural Science Society in Brno. Charles Darwin's provisional hypothesis of pangenesis.
  • 1866 Experiments on Plant Hybrids published based on the 1865 lectures
  • 1868 Friedrich Miescher isolated a new compound from the nuclei of white blood cells which as neither protein or carbohydrate was termed nucleic acid.
  • 1876 Meiosis discovered and described in sea urchin eggs by Oscar Hertwig.
  • 1882 Walther Flemming invents the term mitosis also described slightly earlier by Otto Bütschli
  • 1883 Edouard van Beneden observes that after germ cell fertilization of the nematode Parascaris equorum ( was Ascaris megalocephala) the chromosomes of the male nucleus do not fuse with those of the oocyte nucleus. Therefore chromosomes are distinct entities
  • 1888 Heinrich von Waldeyer first uses the term chromosome. Theodor Boveri describes the centrosome.
  • 1902 Walter Sutton first publishes on the chromosome theory of inheritance. Theodor Boveri first postulates carcinogenesis was the result of aberrant mitoses
  • 1904 The chromosome theory of inheritance is integrated by Wilson, Sutton and Boveri and Mendel is rediscovered
  • 1913 Eleanor Carothers documents evidence of independent assortment of chromosomes in a species of grasshopper. Alfred Sturtevant presents the first chromosome map and the linear arrangement of genes in Drosophila melanogaster[1]
  • 1915 Thomas Hunt Morgan's experiments on Drosophila melanogaster prove chromosome therapy of inheritance
  • 1922 Fisher's studies of how a mutation can invade a population or disappear.
  • 1927 Hermann J. Muller demonstrates that X-rays can induce mutations. John Haldane further describes mutation population dynamics.
  • 1928 Frederick Griffith notes puzzling virulence factors in Streptococcus pneumoniae
  • 1931 Curt Stern commences publication of work on recombination fully integrated in his 1936 paper[2]
  • 1941 George Beadle and Edward Tatum propose "one gene-one enzyme" hypothesis[3]
  • 1944 Oswald Avery, C. M. MacLeod, and M. McCarty isolate Griffith's virulence factor and actually prove DNA must be genetic material but it takes a while for protein hypothesis to die
  • 1952 Alfred Hershey and Martha Chase use 32P and 35S with the bacteriophage T2 infecting E. coli to destroy the protein hypothesis until prion theory becomes necessary much later
  • 1953 Watson and Crick describe structure of DNA neatly bringing it all together[4]
  • 1957 Vernon Ingram and colleagues move from "one gene-one enzyme" hypothesis to "one gene-one polypeptide" hypothesis
  • 1958 DNA confirmed to replicate semi-conservatively in the Meselson–Stahl experiment[5]
  • 1961 Part of genetic code first described with the Nirenberg and Matthaei experiment[6]
  • 1968 DNA sequencing first done[7].
  • 1977 Gene spicing described by Phillip Sharp and Richard J. Roberts confirming a variant of "one gene-one polypeptide" hypothesis in eukaryotes and the later description of the major and minor spliceosomes. Practical methods of DNA sequencing described[8] with first complete viral genome determined by Sanger method[9].
  • 1986 Commercial automated DNA sequencing
  • 1990 On September 14, 1990, the first approved gene therapy procedure in severe combined immunodeficiency took place[10][11].
  • 1995 First bacterial complete sequence
  • 2001 Human genome sequenced
  • 2012 First licensed gene therapy, in Europe, alipogene tiparvovec as a treatment for lipoprotein lipase deficiency. Many follow in a very short space of time, but are not cheap.

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References

  1. Sturtevant, A. H. The linear arrangement of six sex-linked factors in Drosophila, as shown by their mode of association. Journal of Experimental Zoology 14, 43–59 (1913) doi:10.1002/jez.1400140104.
  2. Stern C. Somatic crossing over and segregation in Drosophila melanogaster. Genetics. 1936;21:625–730
  3. Beadle GW, Tatum EL. Genetic Control of Biochemical Reactions in Neurospora. Proceedings of the National Academy of Sciences of the United States of America. 1941 Nov 15; 27(11):499-506.
  4. WATSON JD, CRICK FH. The structure of DNA. Cold Spring Harbor symposia on quantitative biology. 1953; 18:123-31.
  5. Meselson M, Stahl FW. THE REPLICATION OF DNA IN ESCHERICHIA COLI. Proceedings of the National Academy of Sciences of the United States of America. 1958 Jul 15; 44(7):671-82.
  6. NIRENBERG MW, MATTHAEI JH. The dependence of cell-free protein synthesis in E. coli upon naturally occurring or synthetic polyribonucleotides. Proceedings of the National Academy of Sciences of the United States of America. 1961 Oct 15; 47:1588-602.
  7. Wu R, Kaiser AD. Structure and base sequence in the cohesive ends of bacteriophage lambda DNA. Journal of molecular biology. 1968 Aug 14; 35(3):523-37.
  8. Maxam AM, Gilbert W. A new method for sequencing DNA. Proceedings of the National Academy of Sciences of the United States of America. 1977 Feb; 74(2):560-4.
  9. Sanger F, Nicklen S, Coulson AR. DNA sequencing with chain-terminating inhibitors. Proceedings of the National Academy of Sciences of the United States of America. 1977 Dec; 74(12):5463-7.
  10. The ADA human gene therapy clinical protocol. Human gene therapy. 1990 ; 1(3):327-362.(Print)
  11. Blaese RM, Culver KW, Chang L, Anderson WF, Mullen C, Nienhuis A, Carter C, Dunbar C, Leitman S, Berger M. Treatment of severe combined immunodeficiency disease (SCID) due to adenosine deaminase deficiency with CD34+ selected autologous peripheral blood cells transduced with a human ADA gene. Amendment to clinical research project, Project 90-C-195, January 10, 1992. Human gene therapy. 1993 Aug; 4(4):521-527.(Print) (Link to article – subscription may be required.)

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