What is Aneuploidy?

From: ted.held at us.henkel.com (ted.held at us.henkel.com) on 2008.01.07 at 18:01:38(16930) Dear List, I have managed to finish the latest Aroideana. It's probably a good thing for me this comes out only once a year as it seems like it takes me a year to read and digest what's in one. Being a lay person, some of the articles can be heavy-going. The one entitled "The Chromosome Numbers of the Aroid Genera", by Dr. Bogner, is a case in point. I am trying to sort out what the apparent promiscuity of aroids with regard to chromosome numbers might mean. Here are some questions? 1. Do all the plants within a given species have the same basic "X" number of chromosomes? Does this mean a species within the genus Landoltia, for example, might have a normal 2n chromosome count of 40 with haploid (2n = 20), diploid (2n = 80), etc., variations, but not 2n = 46? So if you have two plants, one with 2n = 40 and another with 2n = 46, do you know you have two different species? 2. Can plants with different chromosome counts be cross fertile? Can a 2n = 40 plant produce viable seed with its own diploid? How about with a plant in the same genus with a chromosome count of 2n = 46? 3. What happens when a plant messes up and undergoes aneuploidy. Aneuploidy is defined in the text as when some type of evolution takes place where the offspring end up with a few extra chromosomes here and there. Doesn't this mess up the plant? If not, why not? 4. Similarly, there is a term called dysploidy where a few chromosomes don't make it into the new plants, or where old chromosomes get pieces chewed off, somehow. Don't plants need at least a portion of the information contained in the chromosome arms? Doesn't this mess up the plant? If not, why not? 5. Can a plant that has experienced aneuploidy or dysploidy produce viable seed with a normal-count plant? Or does the plant have to reproduce vegetatively for a while until there is another receptive brother or sister with whom to mate? 6. How much messing around with chromosome numbers does it take before the morphological differences are large enough to produce a new genus? Please take pity on me. When I went to school all this was very new. Come to think of it Darwin was new stuff back in those days. Ted. +More -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.gizmoworks.com/mailman/private/aroid-l/attachments/20080107/0b99f779/attachment.htm

From: lbmkjm at yahoo.com (brian lee) on 2008.01.08 at 09:48:24(16932) Dear Ted, Aloha. I think the best thing for you to do is to look at Botany Online...it will help you on some of the questions you pose. In a nutshell, aneuploidy messes things up. In humans, tumors and Down's Syndrome are examples. In plants, death or deviant growth patterns are observed. Aloha, Leland +More --- ted.held at us.henkel.com wrote: > Dear List, > > I have managed to finish the latest Aroideana. It's > probably a good thing > for me this comes out only once a year as it seems > like it takes me a year > to read and digest what's in one. Being a lay > person, some of the articles > can be heavy-going. The one entitled "The Chromosome > Numbers of the Aroid > Genera", by Dr. Bogner, is a case in point. I am > trying to sort out what > the apparent promiscuity of aroids with regard to > chromosome numbers might > mean. Here are some questions? > > 1. Do all the plants within a given species have the > same basic "X" number > of chromosomes? Does this mean a species within the > genus Landoltia, for > example, might have a normal 2n chromosome count of > 40 with haploid (2n = > 20), diploid (2n = 80), etc., variations, but not 2n > = 46? So if you have > two plants, one with 2n = 40 and another with 2n = > 46, do you know you > have two different species? > 2. Can plants with different chromosome counts be > cross fertile? Can a 2n > = 40 plant produce viable seed with its own diploid? > How about with a > plant in the same genus with a chromosome count of > 2n = 46? > 3. What happens when a plant messes up and undergoes > aneuploidy. > Aneuploidy is defined in the text as when some type > of evolution takes > place where the offspring end up with a few extra > chromosomes here and > there. Doesn't this mess up the plant? If not, why > not? > 4. Similarly, there is a term called dysploidy where > a few chromosomes > don't make it into the new plants, or where old > chromosomes get pieces > chewed off, somehow. Don't plants need at least a > portion of the > information contained in the chromosome arms? > Doesn't this mess up the > plant? If not, why not? > 5. Can a plant that has experienced aneuploidy or > dysploidy produce viable > seed with a normal-count plant? Or does the plant > have to reproduce > vegetatively for a while until there is another > receptive brother or > sister with whom to mate? > 6. How much messing around with chromosome numbers > does it take before the > morphological differences are large enough to > produce a new genus? > > Please take pity on me. When I went to school all > this was very new. Come > to think of it Darwin was new stuff back in those > days. > > Ted. > > _______________________________________________ > Aroid-L mailing list > Aroid-L at www.gizmoworks.com > http://www.gizmoworks.com/mailman/listinfo/aroid-l > ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ

From: Thomas.Croat at mobot.org (Tom Croat) on 2008.01.09 at 20:35:37(16937) Dear Ted: In our breeding studies here at the Missouri Botanical Gardens we have found that intersectional crosses are rare, usually impossible so the chromosome counts are not the only determining factor because several sections share 2n0. Also aneuploidy appears to be in evidence in sect. Porphyrochitonium which has chromosome levels of 28,29,30, 31 for example and these numbers can arrive by unequal crossing and through the production of triploids which can cross because they have a full complement of chromosomes. Really we ought to get Dick Sheffer to expound on this. That is his area of expertice. Tom +More -----Original Message----- From: aroid-l-bounces at gizmoworks.com [mailto:aroid-l-bounces at gizmoworks.com] On Behalf Of brian lee Sent: Tuesday, January 08, 2008 3:48 AM To: Discussion of aroids Subject: Re: [Aroid-l] What is Aneuploidy? Dear Ted, Aloha. I think the best thing for you to do is to look at Botany Online...it will help you on some of the questions you pose. In a nutshell, aneuploidy messes things up. In humans, tumors and Down's Syndrome are examples. In plants, death or deviant growth patterns are observed. Aloha, Leland --- ted.held at us.henkel.com wrote: > Dear List, > > I have managed to finish the latest Aroideana. It's > probably a good thing > for me this comes out only once a year as it seems > like it takes me a year > to read and digest what's in one. Being a lay > person, some of the articles > can be heavy-going. The one entitled "The Chromosome > Numbers of the Aroid > Genera", by Dr. Bogner, is a case in point. I am > trying to sort out what > the apparent promiscuity of aroids with regard to > chromosome numbers might > mean. Here are some questions? > > 1. Do all the plants within a given species have the > same basic "X" number > of chromosomes? Does this mean a species within the > genus Landoltia, for > example, might have a normal 2n chromosome count of > 40 with haploid (2n = > 20), diploid (2n = 80), etc., variations, but not 2n > = 46? So if you have > two plants, one with 2n = 40 and another with 2n = > 46, do you know you > have two different species? > 2. Can plants with different chromosome counts be > cross fertile? Can a 2n > = 40 plant produce viable seed with its own diploid? > How about with a > plant in the same genus with a chromosome count of > 2n = 46? > 3. What happens when a plant messes up and undergoes > aneuploidy. > Aneuploidy is defined in the text as when some type > of evolution takes > place where the offspring end up with a few extra > chromosomes here and > there. Doesn't this mess up the plant? If not, why > not? > 4. Similarly, there is a term called dysploidy where > a few chromosomes > don't make it into the new plants, or where old > chromosomes get pieces > chewed off, somehow. Don't plants need at least a > portion of the > information contained in the chromosome arms? > Doesn't this mess up the > plant? If not, why not? > 5. Can a plant that has experienced aneuploidy or > dysploidy produce viable > seed with a normal-count plant? Or does the plant > have to reproduce > vegetatively for a while until there is another > receptive brother or > sister with whom to mate? > 6. How much messing around with chromosome numbers > does it take before the > morphological differences are large enough to > produce a new genus? > > Please take pity on me. When I went to school all > this was very new. Come > to think of it Darwin was new stuff back in those > days. > > Ted. > > _______________________________________________ > Aroid-L mailing list > Aroid-L at www.gizmoworks.com > http://www.gizmoworks.com/mailman/listinfo/aroid-l > ________________________________________________________________________ ____________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ _______________________________________________ Aroid-L mailing list Aroid-L at www.gizmoworks.com http://www.gizmoworks.com/mailman/listinfo/aroid-l

From: agrsuw at ku.ac.th (agrsuw at ku.ac.th) on 2008.01.10 at 09:49:37(16939) Dear Ted, I really like your questions. I would like to answer your questions as followed: +More 1. Do all the plants within a given species have the same basic "X" number of chromosomes? =Yes. The basic chromosome number ( X or N ) is assigned to a given species or genus. Does this mean a species within the genus Landoltia, for example, might have a normal 2n chromosome count of 40 with haploid (2n = 20), diploid (2n = 80), etc., variations, but not 2n = 46? = Normally, individuals in a species share the same chromosome number. However, some deviation in the number can naturally occur. Aneuploidy is the one with a change in chromosome number (for example 2n = 2N+1, = 2N+1+1, = 2N-, 2N - 1-1) while euploidy is the one with the change in number of chromosome set (for example 2n = N, = 3N, = 4N). By the way, 2n is the chromosome number normally counted from root tip while n (haploid number) is the chromosome number normally counted from anther. In your case, 2n = 80 should be tetraploid, not diploid. So if you have two plants, one with 2n = 40 and another with 2n = 46, do you know you have two different species? = From the chromosome number you gave, it is most likely to be 2 different species. The difference (6) is too high to be an aneuploidy, but you can not tell. In Aglaonema costatum, 2n = 40 and 48. 2. Can plants with different chromosome counts be cross fertile? = Yes, it can, especially with the help of embryo rescue technique. Many slipper orchid species with different chromosome number yielded a number of interspecific hybrids, both primary and complex ones. Can a 2n = 40 plant produce viable seed with its own diploid? = Yes, it can, especially 2n = 2N = 40 since it is diploid. However, the fertility declines if it is tetraploid (2n = 4N). How about with a plant in the same genus with a chromosome count of 2n = 46? = It should be fertile. 3. What happens when a plant messes up and undergoes aneuploidy. Aneuploidy is defined in the text as when some type of evolution takes place where the offspring end up with a few extra chromosomes here and there. Doesn't this mess up the plant? If not, why not? = Normally, an aneuploidy has low fertility. However, a few offsprings of its can regain the fertlity through chromosome doubling. In evolution process, the fittest will survive and establish an population. If the aneuploidy can perform better than the original in survival and reproduction in a new environment, it may evolve to be a new species in a due course. 4. Similarly, there is a term called dysploidy where a few chromosomes don't make it into the new plants, or where old chromosomes get pieces chewed off, somehow. Don't plants need at least a portion of the information contained in the chromosome arms? Doesn't this mess up the plant? If not, why not? = Most of higher plants today are polyploid. It is hypothesized that plants with N > 10 are eupolyploid. Missing a chromosome from eupolyploids may not be lethal. 5. Can a plant that has experienced aneuploidy or dysploidy produce viable seed with a normal-count plant? Or does the plant have to reproduce vegetatively for a while until there is another receptive brother or sister with whom to mate? = As stated above, it is possible that aneuploid can produce some seeds. 6. How much messing around with chromosome numbers does it take before the morphological differences are large enough to produce a new genus? = It is not just the chromosome number. Reproduction organ and crossability are the key different that separate two population to a genus level. You may try look at chromosome number of the genus Aglaonema which varies within the species and genus. The genus is vegetatively propagated in natural condition. I hope my answer can help you clear up your doubt. Regards, Surawit ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.

From: ted.held at us.henkel.com (ted.held at us.henkel.com) on 2008.01.10 at 18:26:37(16942) Dear Surawit, Thank you for your reply. It looks like there is much information"out there" about this science that has been hidden from me all these years. I think I'll try Leland's advice as well, and think about what you have written. My response is humble and I have a number of new questions now that will only add to my perplexity. Here are a few. 1. How reliable are chromosome counts, statistically? How many cells do you need to count before you are satisfied that you have the right number? 2. Is it possible to have a nuisance cell or two that show a different count from others from the same plant? I mean, what do you do if you count, say 20 cells with 2n = 40 and one with 2n = 42? 3. How easy is it to break a chromosome in the process of performing the preparation and root tip crush? I'd better stop now. Ted. +More -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.gizmoworks.com/mailman/private/aroid-l/attachments/20080110/11fc90ae/attachment.htm

From: agrsuw at ku.ac.th (agrsuw at ku.ac.th) on 2008.01.11 at 07:23:43(16944) Dear Ted, The following is my answer to your questions. ] Quoting ted.held at us.henkel.com: +More > 1. How reliable are chromosome counts, statistically? How many cells do > you need to count before you are satisfied that you have the right number? = Some said that the count before 1970s should be recounted due to the old technique was not good enough. In a normall count, we count from at least 5 good cells. "Good cell" means the cells that their chromosome spread out clearly. These cell must have their cell wall intact. The number we finally take is the number from the majority of the cell, not an average. > 2. Is it possible to have a nuisance cell or two that show a different > count from others from the same plant? I mean, what do you do if you > count, say 20 cells with 2n = 40 and one with 2n = 42? = Yes, it is possible that there are some cell with different chromosome number. This phenomenon is called "cytochimera or mixoploidy". From your scenario, 2n = 40 will be the count. > 3. How easy is it to break a chromosome in the process of performing the > preparation and root tip crush? = It is extremly difficult to break a chromosome without crushing the cell wall. I am more than happy to entertain your curiosity. Surawit ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.

From: pjm at gol.com (Peter Matthews) on 2008.01.14 at 03:19:41(16950) Dear Ted, >1. How reliable are chromosome counts, statistically? How many cells do >you need to count before you are satisfied that you have the right number? Some kinds of plants are more stable than others, but many plants (like Colocasia eesculenta - taro) are very stable - i.e. one clear count on one cell from one tip is likely to be the full story. Ferns with hundreds of tiny similar-looking chromosomes are hard to count accurately, and may also be more unstable in terms of number. >2. Is it possible to have a nuisance cell or two that show a different >count from others from the same plant? I mean, what do you do if you >count, say 20 cells with 2n = 40 and one with 2n = 42? Count more cells, confirm, and report! In my experience, this sort of thing is a reflection of poor preparations with spilled chromosomes and difficult, inaccurate counting. If the counts are all clear and accurate, and the unusual number is real, then there could be some interest in counting many more cells to establish a frequency of occurrence, and measure the instability in cell divisions. +More Another way to get at this is to look at chromosome spreads from hundreds of seedlings in an experimental breeding cross, to learn what the natural frequency of aneupleoidy or polyploidy is. Such insanely eye-straining work has actually been done for some plants (including taro, Colocasia esculenta - by a Japanese research group). In the case of taro, it was possible to use this approach experimentally to confirm very low rates of polyploid formation by the rare production of unreduced gametes. I do not remember if aneuploids were also found. >3. How easy is it to break a chromosome in the process of performing the >preparation and root tip crush? It is easier to break the cell membranes, and spill chromosomes across the field of view on a slide - sometimes with the result that it is unclear which cell the chromosome comes from. The individual, fully-condensed chromosomes at metaphase are very resilient in the cell solution, and under the pressures applied a slide preparation, so they do not break. Metaphase chromosomes are what we target, usually, when making chromosome counts. Certain chemicals can be used to arrest cells at this stage in cell division, in order to increase the chance of being able to make a good count. Best regards, Peter Matthews (Kyoto) ****

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