From owner-recombination@net.bio.net Sun Nov 02 22:00:00 1997 Path: biosci!biosci!not-for-mail From: "G. Dellaire" Newsgroups: bionet.molbio.recombination Subject: THE RECOMBINATION NEWS GROUP IS MODERATED Date: 3 Nov 1997 15:13:02 -0800 Organization: BIOSCI International Newsgroups for Molecular Biology Lines: 22 Sender: daemon@net.bio.net Approved: dellaire@odyssee.net Distribution: world Message-ID: <63llpu$lld@net.bio.net> NNTP-Posting-Host: net.bio.net *********************************************** THE RECOMBINATION NEWS GROUP IS MODERATED *********************************************** This means that all messages are screened first and then posted to the group. As a result readers may have noticed a drop in the number of posts, particularly those that were considered SPAM. Many groups on bionet are moderated now to try to stem, what can only be called an onslaught of unwanted e-mail and usenet messages. So although fewer posts make it to the group, those that do are usually relevant to the group and hence worth reposting to the news group proper. Cheers, G. Dellaire Moderator RECOM From owner-recombination@net.bio.net Thu Nov 13 22:00:00 1997 Path: biosci!biosci!not-for-mail From: "Cynthia S. Smagula" Newsgroups: bionet.molbio.recombination Subject: BioToolKit Now Online Date: 14 Nov 1997 04:45:57 -0800 Organization: BioSupplyNet Lines: 14 Sender: daemon@net.bio.net Approved: dellaire@odyssee.net Distribution: world Message-ID: <64hh65$j0d@net.bio.net> Reply-To: biota@biosupplynet.com NNTP-Posting-Host: net.bio.net The BioToolKit, a unique annotated directory of 500 key molecular biology research tools is now available to researchers at http://www.biosupplynet.com/cfdocs/btk/btk.cfm. The BioToolKit locates and annotates molecular biology databases, information retrieval tools, data analysis applications, and structural visualization tools available on the World Wide Web. The three sections, Nucleic Acid Analysis, Genome Resources, and Protein Structural Imaging and Analysis, may be searched or browsed quickly via pop-up menus that group applications by function. No more A-to-Z lists of hundreds of URLs that leave you clueless! The BioToolKit is a unique and fast way to get up-to-date links to key web resources.Tour the BioToolKit at http://www.biosupplynet.com/cfdocs/btk/btk.cfm. From owner-recombination@net.bio.net Sat Nov 15 22:00:00 1997 Path: biosci!biosci!not-for-mail From: "Boris Martchenko" Newsgroups: bionet.molbio.recombination Subject: Crossover at meiosis Date: 16 Nov 1997 15:53:43 -0800 Organization: h s bio f biophys c Lines: 7 Sender: daemon@net.bio.net Approved: dellaire@odyssee.net Distribution: world Message-ID: <64o127$71f@net.bio.net> NNTP-Posting-Host: net.bio.net Hi, all! I have a question: Is the crossingover betveen pairs of homologous chromosomes necessary for successful meiosis, or not? Boris From owner-recombination@net.bio.net Mon Nov 17 22:00:00 1997 Path: biosci!biosci!not-for-mail From: Graham Dellaire Newsgroups: bionet.molbio.recombination Subject: Re: Crossover at meiosis Date: 17 Nov 1997 19:47:50 -0800 Organization: McGill Div. of Experimental Medicine Lines: 74 Sender: daemon@net.bio.net Approved: dellaire@odyssee.net Distribution: world Message-ID: <64r356$jg9@net.bio.net> Reply-To: dellaire@odyssee.net NNTP-Posting-Host: net.bio.net Boris Wrote: >Hi, all! >I have a question: Is the crossingover betveen pairs of homologous >chromosomes >necessary for successful meiosis, or not? Hello Boris, Good question!? I think it is yes and NO... First YES: In mammals we often see chiasmata associated with paired homologs during mieosis. These chiasmata are unresolved recombination intermediates between the DNA strands of each homolog. Now in mammals you require chiasmata formation and presumably cross-over for efficient disjunction. There seems to be a "tension" requirement for the proper segregation of chromosomes and thus chiasmata provide such tension. In yeast there is also a stong correlation between X-overs/Chiasmata and proper segregation. For some recent data on nondisjunction in humans see: Characterization of susceptible chiasma configurations that increase the risk for maternal nondisjunction of chromosome 21. Hum Mol Genet 1997 Sep;6(9):1391-1399 Lamb NE, et al. Now NO: In other species you sometimes do not require chiasmata formation for proper disjunction. This occurs during achiasmatic pairing in Drosophila. So in such cases you don't need cross-over for proper segregation. See: *Requiem for distributive segregation: achiasmate segregation in Drosophila females. Hawley RS, Theurkauf WE Trends Genet 9(9), 310-317 (1993) *There are two mechanisms of achiasmate segregation in Drosophila females, one of which requires heterochromatic homology. Hawley RS et al., Dev Genet 13(6), 440-467 (1992) and *Evidence that intergenic spacer repeats of Drosophila melanogaster rRNA genes function as X-Y pairing sites in male meiosis, and a general model for achiasmatic pairing. McKee BD, Habera L, Vrana JA Genetics 132(2), 529-544 (1992) Apparently you can also have low resolution achiasmatic segregation in Yeast but at low fideltiy see and ref. within: *Effects of homology, size and exchange of the meiotic segregation of model chromosomes in Saccharomyces cerevisiae. Ross LO, Rankin S, Shuster MF, Dawson DS Genetics 1996 Jan;142(1):79-89 Hope this helps. I think some of the Yeast or Drosophila People who browse this thread might have more to say. Graham Dellaire Div. of Exp. Medicine McGill University From owner-recombination@net.bio.net Mon Nov 17 22:00:00 1997 Path: biosci!biosci!not-for-mail From: BIOSCI Administrator Newsgroups: bionet.molbio.recombination Subject: BIOSCI/bionet miniFAQ & Fundraiser Date: 18 Nov 1997 05:39:45 -0800 Organization: BIOSCI International Newsgroups for Molecular Biology Lines: 234 Sender: daemon@net.bio.net Approved: dellaire@odyssee.net Distribution: world Message-ID: <64s5r1$g9l@net.bio.net> NNTP-Posting-Host: net.bio.net (LAST REVISION: 30-JUL-95) This BIOSCI "miniFAQ" is designed to answer the questions that come up the *most frequently*. The main BIOSCI FAQ (Frequently Asked Questions) is accessible on the World Wide Web at URL http://www.bio.net/. If you can not find an answer to your question in this or other documentation, the BIOSCI technical support staff answers e-mail queries sent to biosci-help@net.bio.net We can only answer questions about the use of the newsgroups and mailing lists. We unfortunately do not have the staff to do Internet information searches or answer scientific questions. Please post those to the appropriate BIOSCI/bionet newsgroups. Contents: -------- 0) BIOSCI NEEDS YOUR SUPPORT!! 1) Using the WWW to access the BIOSCI/bionet newsgroups. 2) What to do about "spams," i.e., junk mail, ads, etc. 3) Examples of subscribing and unsubscribing to the mailing lists. 4) The BIOSCI user address and research interest directory. 0) BIOSCI NEEDS YOUR SUPPORT!! ------------------------------ BIOSCI's government funding has been expended, and we are now operating solely from advertising revenue that we have raised from our Web site at http://www.bio.net/. We need just a few minutes of your time to help us serve you. You can do two important things which will take very little time for you individually and will immensely help us continue to help you. First, please use our WWW system at http://www.bio.net/ to access the archives. You can post or reply to messages via your Web browser as described in item #1 below. Your usage helps attract sponsors. If you contact any of our sponsors, please be sure to thank them for supporting BIOSCI. It is critical for them to get this feedback if they are to continue their sponsorship for the long term. Second, if you work for a company or organization that provides products or services of interest to the biology community, please pass this message on to your marketing or marketing communications department or other appropriate group. Please ask them to help support BIOSCI by sponsoring our Web site and explain the uses and benefits of the system to the biology community. If they are interested, they can then contact us for further information at our tech support address, biosci-help@net.bio.net. 1) Using the WWW to access the BIOSCI/bionet newsgroups. -------------------------------------------------------- As of 10 December 1995, all BIOSCI/bionet full newsgroups are accessible through the World Wide Web (WWW) at URL http://www.bio.net. One can read and reply publicly or privately to both recent postings and archived messages through one's Web browser if it is configured properly to send e-mail. Each newsgroup is equipped with its own WAIS index. The main BIOSCI home page also has access to the BIO-JOURNALS Table of Contents database WAIS index and the BIOSCI user address database described in another item further below. 2) What to do about "spams," i.e., junk mail, ads, etc. ------------------------------------------------------- BIOSCI is a set of parallel USENET newsgroups (the "bionet" groups), mailing lists, and a hypermail archive at URL http://www.bio.net/. The same postings are distributed on all media (except for a small number of mailing-list-only groups at net.bio.net). Unfortunately it is becoming a despicable practice on the Internet (by a few people out to make a fast buck) to do automated mass postings to thousands of newsgroups and mailing lists. These attempts to grab free advertising are refered to as "spams" in the usual, somewhat boneheaded, net terminology. USENET is more susceptible to this practice, and many spams originate on the USENET groups and then are passed on to the mailing lists. However, spammers also get lists of mailing addresses and hit these too, so neither medium is immune. What should you do personally if you get junk mail? --------------------------------------------------- Just delete it and move on without reading it further. Filing a protest is becoming increasingly useless because spammers are often disguising the addresses where the messages are sent from. Unless you really understand Internet mail systems, your attempt at protest by sending replies to the message will often end up being sent to the address of an innocent person that the spammer is victimizing. What can BIOSCI/bionet do to protect its newsgroups? ---------------------------------------------------- The only solution currently available is to moderate the newsgroup. If this newsgroup is already moderated, then you are in good shape. Moderation protects the USENET distribution from about 95% of the spams that are being sent to date and protects the mailing lists completely. Moderation means, however, that someone has to take the time to review each message before it goes out. We have set up software here that simply allows the moderator to forward to an address at net.bio.net messages that (s)he wishes to have distributed. This takes no more time than that needed to read the message and pass it on, say about 1 min. per message. Most newsgroups currently have a discussion leader who is responsible for their newsgroup. The discussions leaders and their e-mail addresses are listed in the BIOSCI Information Sheet which is available on the Web at http://www.bio.net/. If a newsgroup is being hit with too many junk postings, please contact the discussion leader for that group and see if there is interest in moderating the group. Please do not assume that by simply posting a complaint to the newsgroup itself, anyone on the BIOSCI staff will act on your complaint. With close to 100 newsgroups to run, the BIOSCI staff has to rely on the discussion leaders of each newsgroup to report problems directly to us at biosci-help@net.bio.net. We will moderate any of our newsgroups if the discussion leader tells us that the readership of the group wishes to do so and if a moderator is willing to do the work. For most BIOSCI/bionet groups, this entails only a few minutes of work each day. Moderating a newsgroup will resolve probably 95% of the junk postings on the USENET distribution. Unfortunately there are easy ways for determined spammers to override the moderation mechanism on USENET, but we can protect our e-mail subscribers from unwanted postings if the newsgroup is moderated. You can also access our newsgroups over the WWW at URL http://www.bio.net. While this Web interface will not stop spammers from trying to post to the groups, this will give you yet another way, besides using USENET news, to keep the junk out of your personal mail files. 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You can fill out the address form directly through our Web page at URL http://www.bio.net/adrform.html. The address database is reindexed nightly for WWW access (the URL is http://www.bio.net/). If you are not directly on the Internet but can reach it by e-mail, please use our waismail server to access the user directory. waismail use is described above. You can also request a user address form by e-mail from biosci-help@net.bio.net. Please check your database entry from time-to-time to see if your address information is still up-to-date. Because of our limited personnel resources, we ask that you resubmit a *complete* form to revise your entry; we only replace complete entries and do not have resources to edit old forms. From owner-recombination@net.bio.net Tue Nov 18 22:00:00 1997 Path: biosci!biosci!not-for-mail From: "Boris Martchenko" Newsgroups: bionet.molbio.recombination Subject: Re: Crossover at meiosis Date: 19 Nov 1997 14:04:11 -0800 Organization: h s bio f biophys c Lines: 8 Sender: daemon@net.bio.net Approved: dellaire@odyssee.net Distribution: world Message-ID: <64vnor$h2g@net.bio.net> NNTP-Posting-Host: net.bio.net Thanks for answers! and I have another question: Gene conversion in mammals: Is it unsuccessful attempt for crossover at meiosis? Boris From owner-recombination@net.bio.net Tue Nov 18 22:00:00 1997 Path: biosci!biosci!not-for-mail From: "G. Dellaire" Newsgroups: bionet.molbio.recombination Subject: Re: Crossover at meiosis Date: 19 Nov 1997 15:16:11 -0800 Organization: BIOSCI International Newsgroups for Molecular Biology Lines: 52 Sender: daemon@net.bio.net Approved: dellaire@odyssee.net Distribution: world Message-ID: <64vrvr$ono@net.bio.net> NNTP-Posting-Host: net.bio.net Hello Boris, you wrote: /Gene conversion in mammals: Is it unsuccessful attempt for crossover at /meiosis? / I think that gene conversion in mammals in somatic cells anyway is the rule rather than the exception. Seems only at last resort do you end up with a cross-over. This is the consensus now I think from a host of gene targeting experiments in cell culture. In mieosis gene conversion occurs when you have transfer of information from one homolog to another in a non-reciprocol fashion. If you initiate pairing by the invasion of single strand ends from one homolog generated from a double or single strand break than you can have gene conversion if the invading single strand molecule primes sythesis using the other homolog (without the break) as a template. In this case you get the formation of what is called a D-loop having one Holliday junction (or possibly two junctions if the other 3' end of the DSB invades). The Holliday junction(s) can migrate or diffuse in either direction and if they reach heterlogous sequence (non matching sequences) the junctions may be nicked by the action of mismatch repair proteins. Such nicking can lead to resolution of the Holliday junction(s) as a crossover or non-crossover events. So I wouldn't consider gene conversion an unsuccessful attempt at cross-over as theoretically both are just as likely to occur during resolution Holliday junction. For a review... which will be clearer than me typing (pictures etc. are infinately helpful in visualizing recombination models) try to find these two papers: Lichten M, 1995 Meiotic recombination hotspots. Annu Rev Genet 29, 423-444 (1995) and Belmaaza A, 1994 One-sided invasion events in homologous recombination at double-strand breaks. Mutat Res 314(3), 199-208 (1994) The later is a good review on recombination in general and has models and discussion of all the relevant recombination mechanisms in yeast and mammals. Graham From owner-recombination@net.bio.net Wed Nov 19 22:00:00 1997 Path: biosci!biosci!not-for-mail From: "G. Dellaire" Newsgroups: bionet.molbio.recombination Subject: EMLJ Job Listing Site to be reviewed by Science! Date: 20 Nov 1997 06:20:03 -0800 Organization: BIOSCI International Newsgroups for Molecular Biology Lines: 48 Sender: daemon@net.bio.net Approved: dellaire@odyssee.net Distribution: world Message-ID: <651guj$3t3@net.bio.net> NNTP-Posting-Host: net.bio.net EMJL TO BE REVIEWED BY SCIENCE MAGAZINE! November 20th, 1997 The Experimental Medicine Job Listing (EMJL)(1) will be reviewed by Science's Next Wave(2) , an electronic publication of Science(3). The review will appear in the 'Site Review' section for a week, starting this Friday November 21st, 1997, and will continue to appear in the'signposts' section for many months to come. Charles Boulakia, Canada Editor of Science's Next Wave, chose EMJL for the next site review which is part of an on going series of reviews of the best science sites on the Internet. (1) http://www.medcor.mcgill.ca/EXPMED/DOCS/jobs.html (2) http://www.nextwave.org (3) http://www.science.com ) Charles Boulakia when asked why EMJL was chosen replied, "I was very impressed by both the quantity and the quality of the information on your site. Keep up the good work!". EMJL has been a broad initiative of several departments at McGill University(4), including: the Department of Medicine, Division of Experimental Medicine; the Faculty of Medicine; and Faculty of Graduate Studies and Research. Job vacancies are listed for positions ranging from chair and faculty positions to openings for Ph.D. candidates and post doctoral studies. As well, extensive links to fellowship information and other career resources are provided. (4) http://www.mcgill.ca Originally designed to aid both McGill faculty and students in filling and finding job vacancies, EMJL has grown into an internationally known web site which, since inception, has received almost half a million visits and successfully filled over 150 job vacancies. Jobs are now listed for positions across North America, Europe and Asia. The Experimental Medicine Job Listing has also been recognized by the National Institutes of Health and is currently the official Job Listing of the Canadian Society of Biochemistry,Molecular and Cellular Biologists. ========================================================================== For further information please visit EMJL* or contact Graham Dellaire** the creator and current webmaster. * http://www.medcor.mcgill.ca/EXPMED/DOCS/jobs.html ** dellaire@microtec.net From owner-recombination@net.bio.net Sat Nov 22 22:00:00 1997 Path: biosci!biosci!not-for-mail From: gordonr@cc.UManitoba.CA (Richard Gordon) Newsgroups: bionet.molbio.recombination Subject: Re: Seeking resources: interorganism genome-size variations. Date: 23 Nov 1997 11:38:16 -0800 Organization: BIOSCI International Newsgroups for Molecular Biology Lines: 25 Sender: daemon@net.bio.net Approved: dellaire@odyssee.net Distribution: world Message-ID: <65a0n8$c6f@net.bio.net> NNTP-Posting-Host: net.bio.net For one hypothesis, try: Martin, C.C. & R. Gordon (1995). Differentiation trees, a junk DNA molecular clock, and the evolution of neoteny in salamanders. J. Evol. Biol. 8, 339-354. >I'm seeking data or other resources which address the reasons causing >the large differences in genome size between diverse organisms (which >appear not to relate to any obvious organismic parameters). > >Any clues, resources, etc. you can provide will be appreciated! > >Thanks, >Dennis -------------------------------------------------------------------- Temporary address until Canadian postal strike ends: Dr. Richard Gordon, Department of Radiology University of Manitoba, P.O. Box 192 Pembina, ND 58271 USA Phone: (204) 789-3828, Fax: (204) 787-2080, Home: (204) 589-0411 E-mail: GordonR@cc.UManitoba.ca