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Nondisjunction is the failure of chromosome pairs to separate properly during meiosis or mitosis. The result of this error is that a chromosome(s) is lost (or gained). When a chromosome is lost, it is called a Monosomy, in which the gamete with the defect will have 1 or more chromosomes missing from one of its pairs. When a chromosome is gained, it is called a Trisomy, in which the gamete will have a set of 24 chromosomes instead of the usual 23. These errors cause Down Syndrome, Turner's Syndrome, Super-Male Syndrome (Extra Y-chromosome on last pair determining sex of the person). There many other Syndromes listed here.
A diagram of 2 possible occurences of non-disjunction in meiosis: (n means 1 copy of each chromosome [haploid cell])
(2n means 2 copies of each chromosome [diploid cell])
4n (duplicated chromosomes in diploid cell) / \ (non-disjunction occurs here) 2n 0n / \ / \ 2n 2n 0 0 (Two gametes have one extra chromosome and the other 2 are missing a chromosome) 4n (duplicated chromosomes in diploid cell) / \ 2n 2n / \ / \ (non-disjunction occurs here) n n 2n 0 (2 Gametes are normal, but on the right side, one gamete has an extra chromosome, and the other is missing one)
Sources:
(Great place for in-depth insight on this subject)
I've changed the introduction to a more suitable definition MickeyK 22:21, 10 December 2006 (UTC)
Wpeissner and I are interested in updating this page and have outlined some possible changes. Feel free to reach out to either of us at our talk pages or directly through here.
1. Our lead section will define nondisjunction. The current article defines nondisjunction as "the failure of chromosome pairs to separate properly during meiosis stage 1 or stage 2, specifically in the anaphase." We could choose to keep this definition or improve upon it from our sources/references.
2. We will also establish context as to why nondisjunction is important. We will need to elaborate on why it is harmful and what it can do as a result of its existence. The current article states, "In the event that an aneuploidic gamete is fertilized, a number of syndromes might result. The only known survivable monosomy is Turner syndrome, where the individual is monosomic for the X chromosome. Examples of trisomies include Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13)." We can research any other known effects of nondisjunction and perhaps give a little more information on the molecular/cellular effects.
3. I've noticed that a lot of good articles on Wikipedia begin with a history. We should see what kind of references we can find on who discovered nondisjunction, when they discovered it, etc.
4. Were there any awards or notable research associated with this discovery? We can probably keep this section relatively short.
1. How is nondisjunction defined; what are characteristic features and consequences of nondisjunction.
2. How is nondisjunction classified according to cell cycle phase (meiosis I, meiosis II, mitosis) and location (germ line versus somatic). This distinction could be clarified by a table.
1. Can we find out physical and molecular signs of of nondisjunction?
2. What medical diseases and syndromes are caused by nondisjunction( trisomies 21, 13, 18, Turner syndrome, Triple X syndrome, etc.). Specific features of relevant syndromes could be listed in bullet points or in table form.
1. If there are multiple causes, we could give it its own section.
2. What is the role of the spindle assembly checkpoint (SAC) and the anaphase promoting factor/cyclosome (APC/C) in the mechanism of nondisjunction? How are these molecular functions affected in aging oocytes?
1. How is it diagnosed?
2. Has the way its been diagnosed changed over time with an increase in technology?
3. What tests, machines, techniques are used to diagnose nondisjunction?
4. What diagnostic tests are currently used in clinical pregnancy screening and in conjunction with in-vitro fertilisation and preimplantation genetic screening? What is the relevance of newly developed diagnistic techniques, like microarray-based comparative genomic hybridization, or SNP analysis.
1. Is there anyway to prevent nondisjunction?
2. What are known risk factors of nondisjunction (e.g. maternal age, affected sibling, family history, ...)
lol — Preceding
unsigned comment added by
2806:263:C402:83D0:81F7:2394:5FAC:B24C (
talk)
00:34, 23 February 2021 (UTC)
1. I have a feeling this may be an non-treatable issues but we could still look into this and give it its own section if warranted.
1. Any current or past research could go here
The topic nondisjunction is closely related to the concepts of Gene dosage and Aneuploidy, among others. The Wikipedia article on Gene dosage currently contains not much more than a single sentence, the article on Aneuploidy lacks suitable inline citations. Explaining the concepts and consequences of nondisjunction will require to either repeat or include explanations of gene dosage and aneuploidy in the nondisjunction article, or to improve these articles and reference them.
1. We could link additional articles at the bottom of ours to provide the reader with similar topics.
Previte01 (
talk)
03:20, 11 March 2014 (UTC)
2. Multimedia content available on the web can be referenced with external links, for example to animations and videos illustrating nondisjunction.
→→Discusses mutations that increase nondisjunction on the X-chromosome. Fifteen mutations in total were studied and characterized.
→→A colony color assay that measures chromosome stability is described and use to study several parameters affecting mitotic maintenance of year chromosomes. The assay distinguishes between chromosome loss and nondisjunction. The assay does this by plating large numbers of single cells and determining the frequency of half-sectored colonies (first-division events) within a population of pink sectoring colonies.
→→They test the hypothesis that is stated in the title of the article using physical and genetic assays.
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Wpeissner (
talk)
02:47, 12 March 2014 (UTC)
Ssumpf ( talk) 13:35, 31 March 2014 (UTC)
Hi guys, great job so far! Here are some suggestions for you on what you've done, please feel free to contact me via email or my talk page if you have any questions about what I've suggested. Thank you!
` I hope this helps you and can't wait to see what you do with the article. Best, Keilana| Parlez ici 16:12, 31 March 2014 (UTC)
CarpeDiem90 ( talk) 22:34, 1 April 2014 (UTC)
You guys have been doing a great job so far, and it looks like the article is really coming along. The comments below are just my suggestions for a couple of ways it might be improved. Keep in mind that they are just suggestions, and if you disagree, or these conflict with other reviewers' suggestions, then do what you think is best.
Good job! Keep up the good work. Klortho ( talk) 19:07, 13 April 2014 (UTC)
Hi! Your article is looking good! Here are a couple suggestions:
Great job so far! This is a big topic- you've definitely got a lot accomplished! Hope these help! Jen
Magladem96 ( talk) 22:09, 13 April 2014 (UTC)
The article is looking to be in great shape so far! I have reviewed your article and have some comments/suggestions that I hope you will find helpful. Please feel free to let me know if any of this information would benefit from further clarification.
Regarding the text, I appreciate the efforts that you have made to present each category clearly and that the categories are logically sequenced. Part of the reason I think that your ideas presented are clear and easy-to-read is that the line lengths are limited to about 30-50 characters and spaces. Your headers are simple and relate clearly to the text that follows. The words and terminology are consistent throughout the document and the sentences are neutral and direct.
I really like the graphic that you have chosen to use that is located near the header. It is helpful in explaining the text, easy to understand, and will be meaningful to the audience. As you continue to develop your article and include additional graphics you may want to consider how to balance the “white space” with words and graphics. This is probably something you are already thinking about but I thought I would mention it just in case.
I like that you have included information about the researchers who are credited with discovering nondisjunction in drosophila sex chromosomes. Would you want to consider giving that paragraph its own header “Discovery”? Just a thought :)
Also, I wanted to mention that I liked how you added an in-line reference for “Polar Body Diagnosis”. Sometimes there just aren’t wiki pages available for scientific terms and so I think that it will be helpful to your reader to be able to easily click and link to a related article that further defines what PBD is.
In the last paragraph “Molecular mechanisms” the last sentence refers to “segration control”. I am not very familiar with “segration” and was wondering if perhaps you meant another term?
As for the “readability” of this article, I wanted to mention that I ran a “Flesch-Kincaid Grade Level” analysis and it appears that it is written at the level of a college sophomore. Whenever possible, you may want to consider simplifying some of the more technical words. The Flesch Reading Ease test results showed that your article received a 29.9 score. This test rates on a 100-point scale and the higher the score, the easier it is to understand the document. You may want to aim for your score to be between 60 and 70. This is only a suggestion and it may be difficult to do given the topic of the article you are expanding.
I have added your article to my “Watchlist” and I look forward to seeing new and interesting information and graphics added as the semester progresses. Great job! DHayes14 ( talk) 16:42, 15 April 2014 (UTC)
Hi, guys! Great job on your article thus far! Below you will find some comments/suggestions for your article:
General Comments
Introduction
Three types of nondisjunction
Molecular mechanisms
Consequences
I noticed on your outline of the article talk page that you initially planned to include a treatment section. Although most of them are incurable, you could lifestyle changes they may have to make. Or rather than discussing treatment options, you could include a research section to discuss ongoing research relevant to curing nondisjunction. Keep up the good work on the article, and please let me know if you have any questions! Kneal0627 ( talk) 18:19, 24 April 2014 (UTC)
I am still confused by the meiosis I and II sections.
where you said "save-guarding" you likely meant safe-guarding.
You may wish to link to advanced maternal age, spontaneous abortion, mental retardation
I it is unclear that "45, X0 karyotype" is the same as "loss of an entire X chromosome". In this sentence number of fetuses does not match the verb: "fetuses are aborted" not "fetuses is aborted".
sec chromosome should read sex chromosome.
Graeme Bartlett ( talk) 11:18, 26 April 2014 (UTC)
Hi! Your article is easy to understand and the images that you have are placed correctly and relevant to the topic. Some suggestions:
Overall great job so far! Gkaltam ( talk) 17:57, 27 April 2014 (UTC)
The comment(s) below were originally left at Talk:Nondisjunction/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.
Rated "high" as highschool/SAT biology content. - tameeria 20:11, 28 April 2007 (UTC) |
Last edited at 20:11, 28 April 2007 (UTC). Substituted at 01:27, 30 April 2016 (UTC)
![]() | This article is rated B-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | ||||||||||||||||
|
Nondisjunction is the failure of chromosome pairs to separate properly during meiosis or mitosis. The result of this error is that a chromosome(s) is lost (or gained). When a chromosome is lost, it is called a Monosomy, in which the gamete with the defect will have 1 or more chromosomes missing from one of its pairs. When a chromosome is gained, it is called a Trisomy, in which the gamete will have a set of 24 chromosomes instead of the usual 23. These errors cause Down Syndrome, Turner's Syndrome, Super-Male Syndrome (Extra Y-chromosome on last pair determining sex of the person). There many other Syndromes listed here.
A diagram of 2 possible occurences of non-disjunction in meiosis: (n means 1 copy of each chromosome [haploid cell])
(2n means 2 copies of each chromosome [diploid cell])
4n (duplicated chromosomes in diploid cell) / \ (non-disjunction occurs here) 2n 0n / \ / \ 2n 2n 0 0 (Two gametes have one extra chromosome and the other 2 are missing a chromosome) 4n (duplicated chromosomes in diploid cell) / \ 2n 2n / \ / \ (non-disjunction occurs here) n n 2n 0 (2 Gametes are normal, but on the right side, one gamete has an extra chromosome, and the other is missing one)
Sources:
(Great place for in-depth insight on this subject)
I've changed the introduction to a more suitable definition MickeyK 22:21, 10 December 2006 (UTC)
Wpeissner and I are interested in updating this page and have outlined some possible changes. Feel free to reach out to either of us at our talk pages or directly through here.
1. Our lead section will define nondisjunction. The current article defines nondisjunction as "the failure of chromosome pairs to separate properly during meiosis stage 1 or stage 2, specifically in the anaphase." We could choose to keep this definition or improve upon it from our sources/references.
2. We will also establish context as to why nondisjunction is important. We will need to elaborate on why it is harmful and what it can do as a result of its existence. The current article states, "In the event that an aneuploidic gamete is fertilized, a number of syndromes might result. The only known survivable monosomy is Turner syndrome, where the individual is monosomic for the X chromosome. Examples of trisomies include Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13)." We can research any other known effects of nondisjunction and perhaps give a little more information on the molecular/cellular effects.
3. I've noticed that a lot of good articles on Wikipedia begin with a history. We should see what kind of references we can find on who discovered nondisjunction, when they discovered it, etc.
4. Were there any awards or notable research associated with this discovery? We can probably keep this section relatively short.
1. How is nondisjunction defined; what are characteristic features and consequences of nondisjunction.
2. How is nondisjunction classified according to cell cycle phase (meiosis I, meiosis II, mitosis) and location (germ line versus somatic). This distinction could be clarified by a table.
1. Can we find out physical and molecular signs of of nondisjunction?
2. What medical diseases and syndromes are caused by nondisjunction( trisomies 21, 13, 18, Turner syndrome, Triple X syndrome, etc.). Specific features of relevant syndromes could be listed in bullet points or in table form.
1. If there are multiple causes, we could give it its own section.
2. What is the role of the spindle assembly checkpoint (SAC) and the anaphase promoting factor/cyclosome (APC/C) in the mechanism of nondisjunction? How are these molecular functions affected in aging oocytes?
1. How is it diagnosed?
2. Has the way its been diagnosed changed over time with an increase in technology?
3. What tests, machines, techniques are used to diagnose nondisjunction?
4. What diagnostic tests are currently used in clinical pregnancy screening and in conjunction with in-vitro fertilisation and preimplantation genetic screening? What is the relevance of newly developed diagnistic techniques, like microarray-based comparative genomic hybridization, or SNP analysis.
1. Is there anyway to prevent nondisjunction?
2. What are known risk factors of nondisjunction (e.g. maternal age, affected sibling, family history, ...)
lol — Preceding
unsigned comment added by
2806:263:C402:83D0:81F7:2394:5FAC:B24C (
talk)
00:34, 23 February 2021 (UTC)
1. I have a feeling this may be an non-treatable issues but we could still look into this and give it its own section if warranted.
1. Any current or past research could go here
The topic nondisjunction is closely related to the concepts of Gene dosage and Aneuploidy, among others. The Wikipedia article on Gene dosage currently contains not much more than a single sentence, the article on Aneuploidy lacks suitable inline citations. Explaining the concepts and consequences of nondisjunction will require to either repeat or include explanations of gene dosage and aneuploidy in the nondisjunction article, or to improve these articles and reference them.
1. We could link additional articles at the bottom of ours to provide the reader with similar topics.
Previte01 (
talk)
03:20, 11 March 2014 (UTC)
2. Multimedia content available on the web can be referenced with external links, for example to animations and videos illustrating nondisjunction.
→→Discusses mutations that increase nondisjunction on the X-chromosome. Fifteen mutations in total were studied and characterized.
→→A colony color assay that measures chromosome stability is described and use to study several parameters affecting mitotic maintenance of year chromosomes. The assay distinguishes between chromosome loss and nondisjunction. The assay does this by plating large numbers of single cells and determining the frequency of half-sectored colonies (first-division events) within a population of pink sectoring colonies.
→→They test the hypothesis that is stated in the title of the article using physical and genetic assays.
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Wpeissner (
talk)
02:47, 12 March 2014 (UTC)
Ssumpf ( talk) 13:35, 31 March 2014 (UTC)
Hi guys, great job so far! Here are some suggestions for you on what you've done, please feel free to contact me via email or my talk page if you have any questions about what I've suggested. Thank you!
` I hope this helps you and can't wait to see what you do with the article. Best, Keilana| Parlez ici 16:12, 31 March 2014 (UTC)
CarpeDiem90 ( talk) 22:34, 1 April 2014 (UTC)
You guys have been doing a great job so far, and it looks like the article is really coming along. The comments below are just my suggestions for a couple of ways it might be improved. Keep in mind that they are just suggestions, and if you disagree, or these conflict with other reviewers' suggestions, then do what you think is best.
Good job! Keep up the good work. Klortho ( talk) 19:07, 13 April 2014 (UTC)
Hi! Your article is looking good! Here are a couple suggestions:
Great job so far! This is a big topic- you've definitely got a lot accomplished! Hope these help! Jen
Magladem96 ( talk) 22:09, 13 April 2014 (UTC)
The article is looking to be in great shape so far! I have reviewed your article and have some comments/suggestions that I hope you will find helpful. Please feel free to let me know if any of this information would benefit from further clarification.
Regarding the text, I appreciate the efforts that you have made to present each category clearly and that the categories are logically sequenced. Part of the reason I think that your ideas presented are clear and easy-to-read is that the line lengths are limited to about 30-50 characters and spaces. Your headers are simple and relate clearly to the text that follows. The words and terminology are consistent throughout the document and the sentences are neutral and direct.
I really like the graphic that you have chosen to use that is located near the header. It is helpful in explaining the text, easy to understand, and will be meaningful to the audience. As you continue to develop your article and include additional graphics you may want to consider how to balance the “white space” with words and graphics. This is probably something you are already thinking about but I thought I would mention it just in case.
I like that you have included information about the researchers who are credited with discovering nondisjunction in drosophila sex chromosomes. Would you want to consider giving that paragraph its own header “Discovery”? Just a thought :)
Also, I wanted to mention that I liked how you added an in-line reference for “Polar Body Diagnosis”. Sometimes there just aren’t wiki pages available for scientific terms and so I think that it will be helpful to your reader to be able to easily click and link to a related article that further defines what PBD is.
In the last paragraph “Molecular mechanisms” the last sentence refers to “segration control”. I am not very familiar with “segration” and was wondering if perhaps you meant another term?
As for the “readability” of this article, I wanted to mention that I ran a “Flesch-Kincaid Grade Level” analysis and it appears that it is written at the level of a college sophomore. Whenever possible, you may want to consider simplifying some of the more technical words. The Flesch Reading Ease test results showed that your article received a 29.9 score. This test rates on a 100-point scale and the higher the score, the easier it is to understand the document. You may want to aim for your score to be between 60 and 70. This is only a suggestion and it may be difficult to do given the topic of the article you are expanding.
I have added your article to my “Watchlist” and I look forward to seeing new and interesting information and graphics added as the semester progresses. Great job! DHayes14 ( talk) 16:42, 15 April 2014 (UTC)
Hi, guys! Great job on your article thus far! Below you will find some comments/suggestions for your article:
General Comments
Introduction
Three types of nondisjunction
Molecular mechanisms
Consequences
I noticed on your outline of the article talk page that you initially planned to include a treatment section. Although most of them are incurable, you could lifestyle changes they may have to make. Or rather than discussing treatment options, you could include a research section to discuss ongoing research relevant to curing nondisjunction. Keep up the good work on the article, and please let me know if you have any questions! Kneal0627 ( talk) 18:19, 24 April 2014 (UTC)
I am still confused by the meiosis I and II sections.
where you said "save-guarding" you likely meant safe-guarding.
You may wish to link to advanced maternal age, spontaneous abortion, mental retardation
I it is unclear that "45, X0 karyotype" is the same as "loss of an entire X chromosome". In this sentence number of fetuses does not match the verb: "fetuses are aborted" not "fetuses is aborted".
sec chromosome should read sex chromosome.
Graeme Bartlett ( talk) 11:18, 26 April 2014 (UTC)
Hi! Your article is easy to understand and the images that you have are placed correctly and relevant to the topic. Some suggestions:
Overall great job so far! Gkaltam ( talk) 17:57, 27 April 2014 (UTC)
The comment(s) below were originally left at Talk:Nondisjunction/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.
Rated "high" as highschool/SAT biology content. - tameeria 20:11, 28 April 2007 (UTC) |
Last edited at 20:11, 28 April 2007 (UTC). Substituted at 01:27, 30 April 2016 (UTC)