Sample Discussion
Subject: Gene mapping: origin, development, status, etc.
From: PHirth <PHirth_at_aol.com> Date: Wed, 4 Mar 1998 18:10:17 EST To: angenmap_at_iastate.edu Subject: Homework When did gene mapping get dicovered? by whom? how? What was thought about it? What important people played a part in this discovery? How were they a part? What was it used for then? |
From: "James Womack" <jwomack_at_CVM.TAMU.EDU> Date: Thu, 05 Mar 1998 10:12:54 -0600 To: angenmap_at_iastate.edu Subject: Re: Homework For PHirth (homework). The first gene map was published by Alfred H. Sturtevant in 1913. The map included six genes for such things as eye color, wing shape, and body size and color on the x-chromosome of the fruit fly, Drosophila melanogaster. Drosophila was one of very few animal species that could be manipulated for genetic analysis at the time and remains a very important organism for genetic research today. The map was based on the fact that these six genes did not segregate independently of each other in meiosis (cell division leading to the production of sperm and eggs -eggs in this case). They behaved as if they were on the same chromosome (or genetically "linked"), a fact that Sturtevant might not have recognized except for the observation of chromosomes by a number of microscopists in the late 1800s and Walter Sutton's recognition in 1903 that Mendel's rules of inheritance were related to chromosomal distribution during meiosis. Thomas Hunt Morgan received the 1933 Nobel Prize (the first for a geneticist) for his expansion and proof of Sutton's ideas and for first demonstrating a gene was located on the x-chromosome of Drosophila. Morgan was Sturtevant's advisor: I forgot to mention that Sturtevant began this work as an undergraduate student at Columbia University. So, back to the map; the linked genes were ordered on the x-chromosome based on the frequency with which they recombined (due to crossing-over between the two x-chromosomes in the female producing the eggs). Genes far apart on a chromosome recombine more frequently than those close together. The units of the map were the frequency of recombination between pairs of genes. We now honor Morgan and designate one percent recombination on our linkage maps as one "centiMorgan". The principles of Sturtevant's map remain the basis for building genetic (linkage) maps in a variety of species today. J.B.S. Haldane examined human pedigrees in 1937 and estimated the distance between the genes for color blindness and hemophilia on the human x-chromosome (the first human gene map). Jan Mohr discovered linkage of traits on a chromosome other than the x (autosomal linkage) in humans in 1951. There are now many refinements for building linkage maps, the more important being powerful statistical tools for pedigree analysis and molecular techniques for the identification of variants in genes or DNA sequences. There are also many new ways to map genes other than by linkage, such as hybridizing microscopically visable probes directly to chromosomes. Only in the last decade have we had human genetic maps that permit genetic counseling for inherited diseases based on nearby markers on the linkage map. These maps also led us into the current era of discovery of the actual genes responsible for the diseases. We are also beginning to use maps of agriculturally important plants and animals to find markers for traits of interest and also to identify the genes responsible for the traits. Like most things in science, there was no practical application of the discoveries of Sturtevant, Morgan and others at the time their work was published. It was just new basic knowledge about the biology of plants and animals. Here we are 85 years later making practical use of these important discoveries. As to your question of what was thought of the work at the time, I suspect it was appreciated only by other scientists and not at all by the general public. I hope in your homework assignment you will find occassion to discuss the time lag between basic scientific discovery and practical benefits to society. I'm afraid this fact is no more appreciated today than it was then. Good luck. Jim Womack P.S. I just read Andy Law's response which is a review of much more recent history than is mine. I believe if you piece the two together you will have a good idea of just how many scientific advances were required to get from the basic concept in 1913 to the various practical applications in 1998. |
From: "Mary E. Delany" <medelany_at_ucdavis.edu> Date: Thu, 5 Mar 1998 12:16:26 -0600 To: mappers_at_iastate.edu Subject: Re: Homework Some points and hallmarks that might help: Bateson coined the term "genetics" (note that later he resisted the idea of the chromsomal basis for the units of heredity! He also coined homozygote and heterozygote, F1, F2). Bateson and Punnett (1904) first reported nonrandom assortment (they didn't know it was linkage, thought it was "replusion" of characters from opposite parents). It was inside Thomas Hunt Morgan's lab (ca. 1910 on at Columbia) that the experimental evidence grew that the chromosomes were the mechanism for inheritance. (He wrote "Theory of the Gene"). Sturtevant provided exptl evidence for linkage in Drosophila and apparently gets credit for producing the first genetic map (a Drosphila genetic map (1913). W. Johannsen (studied beans) is credited for coining the terms "phenotype and genotype" and coined the word "gene" (1909). During the first 20-30 years of this century Poultry genetics (several land grant institutions), drosophila genetics (Morgan's lab), maize genetics (Cornell: McClintock and others) associated genes/characters with particular chromosomes and linked them (=gene mapping). (apologies if I've missed a group). In lieu of revisiting the original texts and research articles, King and Stansfield's "A Dictionary of Genetics", 5th edition has a very useful timeline, however I would say in a strong fashion that IT DOES NOT CHRONICLE THE CONTRIBUTIONS OF LIVESTOCK/AGRICULTURAL RESEARCH to the fields of genetics, cytogenetics, etc. --Mary Delany. |
From: "andy.law" <andy.law_at_bbsrc.ac.uk> Subject: RE: Homework To: angenmap_at_iastate.edu Date: Thu, 5 Mar 98 09:15:42 +0000 Dear P? I'm sorry. Although I work on Gene Mapping Projects, I haven't got the first clue who was the first to try it. Its a pretty old concept though - there are some phenotypic loci (feather colour in chickens etc) that were 'mapped' in the early part of the 20th Century. The first published chicken genetic linkage map was by one F.B.Hutt in 1936. For a review of chicken genetic mapping, I suggest you get hold of a review published in Trends in Genetics (1995) Volume 11, part 5 pages 190-194. For pigs, the current key author names to search for are A.L.Archibald, L.Anderson (spelling?) and M.F.Rothschild. If you get one of their review papers, you should be able to work backwards through the references they provide. If you need any help on current methodologies (and databases - thats my involvement), then get back to me. Later, Andy Law |
Date: Thu, 5 Mar 1998 17:50:11 +0100 To: angenmap_at_iastate.edu From: Ingrid.Olsaker_at_veths.no (Ingrid Olsaker) Subject: RE: Homework I would suggest to consult a textbook in general genetics. There you will find information about Mendel and pea-plants as well as Drosophila and Tomas Hunt Morgan among others. (Anyone heard about cM = centiMorgan?) Ingrid |
Date: Fri, 13 Mar 1998 09:24:27 -0500 To: mappers_at_iastate.edu (AnGenMap) From: Lyman / Margaret Crittenden <crittend_at_itis.com> Subject: Homework More Homework Another source of information on genetic mapping and other approaches to mapping such as physical mapping and sequencing is a Primer on Molecular Genetics put for the Human Genome Project by the Department of Energy. This can be found on the Web at: http://www.ornl.gov/hgmis/publicat/primer/intro.html I think you can get a print copy form The Human Genome Management Information System, Oak Ridge National Laboratory, 1060 Commerce Park, Oak Ridge, TN 37830 or by e-mail bkq_at_ornl.gov. Lyman B. Crittenden |
Date: Fri, 13 Mar 1998 15:47:47 -0600 To: angenmap_at_iastate.edu From: Zhiliang Hu <zlhu_at_iastate.edu> Subject: Re: Homework At 03:07 PM 3/13/98 -0600, Margaret Crittenden |
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