History of genetics 1763082 225226239 2008-07-12T15:48:37Z WordyGirl90 4850721 /* The genomics era */ Rmv wikilink...it is already earlier in paragraph [[Image:Mendel.png|frame|right|[[Gregor Mendel]], the "father of genetics"]] The '''history of [[genetics]]''' is generally held to have started with the work of an [[Augustinian]] [[monk]], [[Gregor Mendel]]. [[Experiments on Plant Hybridization|His work]] on pea plants, published in 1866, described what came to be known as [[Mendelian inheritance]]. In the centuries before&mdash;and for several decades after&mdash;Mendel's work, a wide variety of theories of [[heredity]] proliferated (see below). 1900 marked the "rediscovery of Mendel" by [[Hugo de Vries]], [[Carl Correns]] and [[Erich von Tschermak]], and by 1915 the basic principles of Mendelian genetics had been applied to a wide variety of organisms&mdash;most notably the fruit fly ''[[Drosophila melanogaster]]''. Led by [[Thomas Hunt Morgan]] and his fellow "drosophilists", geneticists developed the [[Mendelian-chromosome theory of heredity]], which was widely accepted by 1925. Alongside experimental work, mathematicians developed the statistical framework of [[population genetics]], bring genetical explanations into the study of [[evolution]]. With the basic patterns of genetic inheritance established, many biologists turned to investigations of the physical nature of the [[gene]]. In the 1940s and early 1950s, experiments pointed to [[DNA]] as the portion of chromosomes (and perhaps other nucleoproteins) that held genes. A focus on new model organisms such as viruses and bacteria, along with the discovery of the double helical structure of DNA in 1953, marked the transition to the era of [[molecular genetics]]. In the following years, chemists developed techniques for sequencing both nucleic acids and proteins, while others worked out the relationship between the two forms of biological molecules: the [[genetic code]]. The regulation of [[gene expression]] became a central issue in the 1960s; by the 1970s gene expression could be controlled and manipulated through [[genetic engineering]]. In the last decades of the 20th century, many biologists focused on large-scale genetics projects, sequencing entire genomes. == Pre-Mendelian ideas on heredity == {{see also|Heredity}} ===Ancient theories=== The most influential early theories of heredity were that of [[Hippocrates]] and [[Aristotle]]. Hippocrates' theory (possibly based on the teachings of [[Anaxagoras]]) was similar to Darwin's later ideas on [[pangenesis]], involving heredity material that collects from throughout the body. Aristotle suggested instead that the (nonphysical) [[Eidos|form-giving principle]] of an organism was transmitted through semen (which he considered to be a purified form of blood) and the mother's menstrual blood, which interacted in the womb to direct an organism's early development. For both Hippocrates and Aristotle&mdash;and nearly all Western scholars through to the late 19th century&mdash;the [[inheritance of acquired characters]] was a supposedly well-established fact that any adequate theory of heredity had to explain. At the same time, individual species were taken to have a [[essentialism|fixed essence]]; such inherited changes were merely superficial.<ref>Mayr, ''The Growth of Biological Thought'', pp 635-640</ref> ===Plant systematics and hybridization=== {{see also|History of plant systematics}} In the 18th century, with increased knowledge of plant and animal diversity and the accompanying increased focus on [[taxonomy]], new ideas about heredity began to appear. [[Linnaeus]] and others (among them [[Joseph Gottlieb Kölreuter]], [[Carl Friedrich von Gärtner]], and [[Charles Naudin]]) conducted extensive experiments with hybridization, especially species [[Hybrid (biology)|hybrids]]. Species hybridizers described a wide variety of inheritance phenomena, include hybrid sterility and the high variability of [[back-crossing|back-crosses]].<ref>Mayr, ''The Growth of Biological Thought'', pp 640-649</ref> Plant breeders were also developing an array of stable [[Variety (botany)|varieties]] in many important plant species. In the early 19th century, [[Augustin Sageret]] established the concept of [[Dominance relationship|dominance]], recognizing that when some plant varieties are crossed, certain characters (present in one parent) usually appear in the offspring; he also found that some ancestral characters found in neither parent may appear in offspring. However, plant breeders made little attempt to establish a theoretical foundation for their work or to share their knowledge with current work of physiology.<ref>Mayr, ''The Growth of Biological Thought'', pp 649-651</ref> == Mendel == In breeding experiments between 1856 and 1865, [[Gregor Mendel]] first traced inheritance patterns of certain traits in pea plants and showed that they obeyed simple statistical rules. Although not all features show these patterns of [[Mendelian inheritance]], his work acted as a proof that application of statistics to inheritance could be highly useful. Since that time many more complex forms of inheritance have been demonstrated. From his statistical analysis Mendel defined a concept that he described as an ''[[allele]]'', which was the fundamental unit of heredity. The term ''allele'' as Mendel used it{{Fact|date=February 2007}} is nearly synonymous with the term ''gene'', and now means a specific variant of a particular gene. Mendel's work was published in 1866 as ''"Versuche über Pflanzen-Hybriden" ([[Experiments on Plant Hybridization]])'' in the ''Verhandlungen des Naturforschenden Vereins zu Brünn (Proceedings of the Natural History Society of Brünn)'', following two lectures he gave on the work in early 1865. == Post-Mendel, pre-re-discovery== Mendel's work was published in a relatively obscure [[scientific journal]], and it was not given any attention in the scientific community. Instead, discussions about modes of heredity were galvanized by [[Charles Darwin|Darwin]]'s theory of [[evolution]] by natural selection, in which mechanisms of non-[[Lamarckian]] heredity seemed to be required. Darwin's own theory of heredity, [[pangenesis]], did not meet with any large degree of acceptance. A more mathematical version of pangenesis, one which dropped much of Darwin's Lamarckian holdovers, was developed as the "biometrical" school of heredity by Darwin's cousin, [[Francis Galton]]. Under Galton and his successor [[Karl Pearson]], the biometrical school attempted to build statistical models for heredity and evolution, with some limited but real success, though the exact methods of heredity were unknown and largely unquestioned. == Classical genetics == The significance of Mendel's work was not understood until early in the twentieth century, after his death, when his research was re-discovered by other scientists working on similar problems. [[Hugo de Vries]], [[Carl Correns]] and [[Erich von Tschermak]] There was then a feud between [[William Bateson|Bateson]] and [[Karl Pearson|Pearson]] over the hereditary mechanism. [[Ronald Fisher|Fisher]] solved this in [[The Correlation Between Relatives on the Supposition of Mendelian Inheritance]] :[[1865]] [[Gregor Mendel]]'s paper, ''[[Experiments on Plant Hybridization]]'' :[[1869]] [[Friedrich Miescher]] discovers a weak acid in the nuclei of [[Leukocyte|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"<ref name="pangen">Vries, H. de (1889) ''Intracellular Pangenesis'' [http://www.esp.org/books/devries/pangenesis/facsimile/] ("pan-gene" definition on page 7 and 40 of this 1910 translation in English)</ref> :[[1903]] [[Walter Sutton]] hypothesizes that chromosomes, which segregate in a Mendelian fashion, are hereditary units<ref name="100 Years Ago: Walter Sutton and the Chromosome Theory of Heredity">{{cite journal | author=Ernest W. Crow and James F. Crow| title=100 Years Ago: Walter Sutton and the Chromosome Theory of Heredity| journal=Genetics| year=2002| volume=160| url=http://www.genetics.org/cgi/content/full/160/1/1| pages=1–4| pmid=11805039}}</ref> :[[1905]] [[William Bateson]] coins the term "genetics" in a letter to [[Adam Sedgwick]]<ref>[http://www.jic.ac.uk/corporate/about/bateson.htm Online copy of William Bateson's letter to Adam Sedgwick]</ref> and at a meeting in 1906<ref name="bateson_genetics">{{cite conference | author=Bateson, William | title=The Progress of Genetic Research |editor=Wilks, W. (editor) | booktitle=Report of the Third 1906 International Conference on Genetics: Hybridization (the cross-breeding of genera or species), the cross-breeding of varieties, and general plant breeding|publisher=Royal Horticultural Society | location=London | year=1907}} :Although the conference was titled "International Conference on Hybridisation and Plant Breeding", Wilks changed the title for publication as a result of Bateson's speech.</ref> :[[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 map]]s 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. See [[population genetics]]. :[[1928]] [[Frederick Griffith]] discovers that hereditary material from dead [[bacteria]] can be incorporated into live bacteria (see [[Griffiths experiment]]) :[[1931]] [[Chromosomal crossover|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 [[protein]]s; see the original [[central dogma of genetics]] == The DNA era == [[Image:JamesDWatson.jpg|thumb|James Watson and colleagues discovered the structure of DNA]] :[[1944]] [[Oswald Theodore Avery]], [[Colin McLeod]] and [[Maclyn McCarty]] isolate [[DNA]] as the genetic material (at that time called [[transforming principle]])<ref name="dna_transforming">{{cite journal | author=Avery, MacLeod, and McCarty| title=Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types: Induction of Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III| journal=Journal of Experimental Medicine| year=1944| volume=79| issue=1| pages=137–58| doi=10.1084/jem.79.2.137}}[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=33226 35th anniversary reprint available]</ref> :[[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). [[Barbara McClintock]] discovers [[transposon]]s in [[maize]] :[[1952]] The [[Hershey-Chase experiment]] proves the genetic information of [[phage]]s (and all other organisms) to be DNA :[[1953]] DNA structure is resolved to be a double [[helix]] by [[James D. Watson]] and [[Francis Crick]]<ref>Watson JD, Crick FH, Molecular structure of nucleic acids; a structure for deoxyribose nucleic acid, Nature. 1953 Apr 25;171(4356):737-8</ref> :[[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 [[semiconservative replication|semiconservatively replicated]] :[[1961]]-[[1967]] Combined efforts of scientists "crack" the [[genetic code]], including [[Marshall Nirenberg]], [[Har Gobind Khorana]], [[Sydney Brenner]] & [[Francis Crick]] :[[1964]] [[Howard Temin]] showed using [[RNA virus]]es that the direction of DNA to RNA transcription can be reversed :[[1970]] [[Restriction enzyme]]s were discovered in studies of a bacterium, ''[[Haemophilus influenzae]]'', enabling scientists to cut and paste DNA == The genomics era == See [[genomics]], [[history of genomics]] :[[1972]], [[Walter Fiers]] and his team at the Laboratory of Molecular Biology of the [[University of Ghent]] ([[Ghent]], [[Belgium]]) were the first to determine the sequence of a gene: the gene for [[bacteriophage MS2]] coat protein.<ref>Min Jou W, Haegeman G, Ysebaert M, Fiers W., Nucleotide sequence of the gene coding for the bacteriophage MS2 coat protein, Nature. 1972 May 12;237(5350):82-8</ref> :[[1976]], [[Walter Fiers]] and his team determine the complete nucleotide-sequence of bacteriophage MS2-RNA<ref>Fiers W et al., Complete nucleotide-sequence of bacteriophage MS2-RNA - primary and secondary structure of replicase gene, Nature, 260, 500-507, 1976</ref> :[[1977]] DNA is [[sequencing|sequenced]] for the first time by [[Fred Sanger]], [[Walter Gilbert]], and [[Allan Maxam]] working independently. Sanger's lab sequence the entire [[genome]] of [[Phi X 174|bacteriophage Φ-X174]].<ref>Sanger F, Air GM, Barrell BG, Brown NL, Coulson AR, Fiddes CA, Hutchison CA, Slocombe PM, Smith M., Nucleotide sequence of bacteriophage phi X174 DNA, Nature. 1977 Feb 24;265(5596):687-95</ref> :[[1983]] [[Kary Banks Mullis]] discovers the [[polymerase chain reaction]] enabling the easy amplification of DNA :[[1989]] The [[human]] gene that encodes the [[Cystic fibrosis transmembrane conductance regulator|CFTR]] protein was sequenced by [[Francis Collins (geneticist)|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 :[[2001]] First draft sequences of the human genome are released simultaneously by the [[Human Genome Project]] and [[Celera Genomics]]. :[[2003]] ([[14 April]]) Successful completion of Human Genome Project with 99% of the genome sequenced to a 99.99% [[accuracy]] [http://www.genoscope.cns.fr/externe/English/Actualites/Presse/HGP/HGP_press_release-140403.pdf] ==See also== *[[List of sequenced eukaryotic genomes]] ==External links== * [http://www.mendelweb.org/MWolby.html Olby's "Mendel, Mendelism, and Genetics," at MendelWeb] * http://www.accessexcellence.org/AE/AEPC/WWC/1994/geneticstln.html * http://www.esp.org/books/sturt/history/ * http://cogweb.ucla.edu/ep/DNA_history.html * http://news.bbc.co.uk/1/hi/in_depth/sci_tech/2000/human_genome/749026.stm ==Further reading== * [[Elof Axel Carlson]], ''Mendel's Legacy: The Origin of Classical Genetics'' (Cold Spring Harbor Laboratory Press, 2004.) ISBN 0-87969-675-3 ==References== <references/> {{History of biology}} [[Category:Genetics| ]] [[Category:History of science]] [[Category:History of biology|Genetics]] [[es:Historia de la genética]] [[hu:A genetika története]] [[ru:История генетики]] [[sk:Dejiny genetiky]]