Talk:Nondisjunction

Article draft and notes

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)

Human Genetics 1

Genetics Home Referenceduh

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.

Lead Section

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.

Terminology

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.

Signs and Symptoms

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.

Causes and mechanisms

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?

Diagnosis

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.

Risk factors and prevention

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)

Treatment

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.

Research

1. Any current or past research could go here

Related topics

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.

Further Reading

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.

Selected literature for topic "Nondisjunction"

Textbooks

• "Avery's Diseases of the Newborn, Chapter 20, Specific Chromosome Disorders in Newborns"

→ Provides a systematic overview of various causes of aneuploidy. Differentiates between nondisjunction-induced aneuploidy and partial aneuploidies caused by unbalanced rearrangements, (micro)deletions etc.

→ Describes the nondisjunction-related syndromes trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), trisomy 13 (Patau syndrome), Turner syndrome (45,X0), triploidy (69,XXX or 69,XXY).

• "Human molecular genetics"

→ Systematic explanation of nondisjunction-related terminology: polyploidy, aneuploidy, triploidy, trisomy, monosomy, mosaicism, chimerism.

→ Overview of clinical consequences of numerical chromosome abnormalities.

• "The Metabolic and Molecular Bases of Inherited Disease"

→ The authoritative handbook on molecular and clinical aspects of inherited disease, available in printed and online format.

→ Has at least three chapters relevant to the topic:

65 - Molecular Cytogenetics of Contiguous Gene Syndromes: Mechanisms and Consequences of Gene Dosage Imbalance

63 - Down Syndrome (Trisomy 21)

36 - Retinoblastoma (Cytogenetics, nondisjunction and deletion)

Review articles

• "Etiology of nondisjunction in humans"

→ Describes and discusses various causes of nondisjunction in humans: recombination and nondisjunction, maternal meiosis I nondisjunction, maternal meiosis II nondisjunction, paternal nondisjunction.

→ Proposes models of maternal age-related nondisjunction.

• "Preimplantation genetic diagnosis: state of the art 2011"

→ Describes current diagnostic techniques of preimplantation genetic screening for aneuploidy that can be offered to parents at increased risk (e.g. previous affected child, known family history, disorder diagnosed in one of the parents).

→ Reviews preimplantation screening methodology, including embryo biopsy, blastocyst biopsy, and molecular techniques: PCR and multiplex PCR, analysis of microsatellite markers, linkage analysis, whole genome amplification, microarray-based comparative genomic hybridization, SNP arrays.

• "Preimplantation genetic screening: does it help or hinder IVF treatment and what is the role of the embryo?"

→ Discusses the value of preimplantation genetic screening for improving the success rate of IVF treatment; compares and weighs the benefits and problems of various techniques against each other.

• "Nondisjunction in trisomy 21: origin and mechanisms"

→ Short overview of terminology, mechanisms and risk factors of nondisjunction in trisomy 21.

• "Risk factors for nondisjunction of trisomy 21"

→ Discusses the influence of age and other additional risk factors (health and environment-related) on the occurrence of nondisjunction in the development of trisomy 21.

• "Oocyte ageing and its cellular basis"

→ Current review on molecular mechanisms explaining the increased frequency of nondisjunction occurring in aging oocytes. Points to precocious chromatid separation as an important cause of aneuploidy and discusses increased permissiveness of the spindle assembly checkpoint despite improperly aligned chromosomes as a potential cause of nondisjunction in aging oocytes.

• "A review of trisomy X (47,XXX)"

→ Trisomy X is caused by the presence of an additional X chromosome. The variable phenotype of this syndrome is described in this review, including epidemiology, physical and medical features, psychological characteristics, findings in neuroimaging studies, genetics, etiology, diagnosis and prognosis.

• "Origin and mechanisms of non-disjunction in human autosomal trisomies"

→ Reviews specific differences in nondisjunction in the causation of several autosomal trisomies (8, 13, 15, 16, 18, and 21) and highlights syndrome-specific differences in disease mechanisms (meiosis I vs meiosis II, and maternal vs paternal nondisjunction).

• "Spindle formation, chromosome segregation and the spindle checkpoint in mammalian oocytes and susceptibility to meiotic error."

→ Review examining the contribution of the spindle assembly checkpoint (SAC) and the anaphase promoting factor/cyclosome (APC/C) to proper chromosome segregation during meiosis and mitosis.

→ Discusses age-related reduction in expression of SAC components in mammalian oocytes as possible causes of segregation errors.

• "Nondisjunction Mutants of the Nematode CAENORHABDITIS ELEGANS."
  

→→Discusses mutations that increase nondisjunction on the X-chromosome. Fifteen mutations in total were studied and characterized.

• "Mitotic stability of yeast chromosomes: a colony color assay that measures nondisjunction and chromosome loss."
  

→→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.

• "DNA topoisomerase II must act at mitosis to prevent nondisjunction and chromosome breakage."
  

→→They test the hypothesis that is stated in the title of the article using physical and genetic assays.

References

Wpeissner (talk) 02:47, 12 March 2014 (UTC)

Comments from SSumpf

• Great progress on the article. The language is neutral, unbiased, and informative. The image you have is great!
• In the current stage of the article, there is no lead section which comes before the table of contents and the first heading, so I would suggest to change the definition/terminology section into a newly created lead section for your next submission.
• The content accurately represents cited sources. In the definition/terminology section, I would like to see sources 1,2,&3 come after each statement in which it belongs as opposed to after the entire paragraph.
• The first sentence in the definition/terminology section could be a little confusing, so you could try to water it down a little for the reader and introduce terminology such as germ line cells or somatic cells. Also, since you state “failure of a pair or homologous chromosomes to separate in meiosis I, or the failure of sister chromatids to separate during meiosis II or mitosis ”, I would list meiosis 1, meiosis II, and mitosis in the same order in the next section of your article. It may also make sense to switch the order of the section headings diagnosis and molecular mechanisms so that we have read the mechanisms section prior to the diagnosis section.
• I would love to learn more about the blastomere biopsy you reference in the Diagnosis section. Is this a treatment? If so, you could expand the section heading to be Diagnosis and treatment. You could also add a “See Also” section that links to other pages like trisomy or polysomy, but that could be redundant for terms you refer to directly in the article.
• This article has been improved and I look forward to seeing it progress.

Ssumpf (talk) 13:35, 31 March 2014 (UTC)

Thank you SSumpf for your critique and feedback. The lead section of the article will constantly be updated as we add new information to the wiki page. We have already started fine tuning it. You bring up a good point for sources 1,2, & 3 coming after each statement. We are also attempting at watering down a lot of the terminology as your have mentioned. Several others have suggested this to us as well. I am currently adding wiki links for appropriate words. We will introduce new terminology as necessary. I will continue to work on the diagnosis section because like you, I am fascinated by it as well. Thanks again for your insight. We will continue to improve with your help. Previte01 (talk) 02:09, 9 April 2014 (UTC)

I love the improvements! I would love to see a picture of the diagnostic techniques, or better yet, a video! I wonder if video is going to be incorporated more in this online format in the future. --Ssumpf (talk) 03:00, 9 April 2014 (UTC)

Thank you SSumpf for your valuable input, we made re-organizations and added explanations as you suggested. Wpeissner (talk) 03:22, 9 April 2014 (UTC)

Have you found any additional pictures for nondisjunction? I am having difficulty myself and was thinking about making my own. I would love to see more images for your article. I can relate with having difficulty watering down the language of the wiki articles. I think images help the visual learners out there. --Ssumpf (talk) 17:14, 21 April 2014 (UTC)

Looks like you enlarged the image for nondisjunction - very interesting. I would still love to see more images before your final post, but the article looks good overall!Ssumpf (talk) 19:19, 3 May 2014 (UTC)

Comments from Keilana

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!

• You need to write a lead to the article. Check out that link and look at some other articles to see what a lead should look like. Basically it's a summary/introduction to the article.
• Your citations in the first section are appearing for some reason below the first paragraph, try to make them appear at the end of the first paragraph instead. Ping me if you need help.
• You need a lot more wikilinks and should try to simplify the language a little more. Think about a smart 15-year-old with basic science knowledge reading this article.

` 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)

Thank you Keilana for your advice. I am currently working on wiki-linking and simplifying the language. I get frustrated when I read certain articles and fifty percent of what I read goes right over my head. I will use that experience to fine tune what we are working on. As for the lead, we will constantly continue to update it. I beleive Wpeissner was able to fix the citations problem you mentioned in your second bullet point. Thank you for pointing that out. Previte01 (talk) 02:23, 9 April 2014 (UTC)

Thank you Keilana, your comments are very welcome. We responded to all of your suggestions. The hardest parts seems to be the simplification of the language and terminology - the only thing that is worse than being complicated is being incorrect. But I definitely agree with you that the article should be easier to follow and we will continue working on that. Thanks, Wpeissner (talk) 03:18, 9 April 2014 (UTC)

Comments from CarpeDiem90

• Great beginning outline to the article.
• I am confused as to whether you have made any actual changes on the article itself. It seems that on the article, you have a different layout on the article, than the outline that you have proposed on the article's talk page itself. If this is so, maybe it is time to move the outline to the actual article from the talk page, even though it may seem like a minor change, it will be less confusing to the peer reviewers.
• Having said that, the outline on the talkpage is much more in-depth and I like the direction that you are taking the article to. With its lead sections, mechanisms etc.
• Since it is a molecular biology article, personally I think you could focus more on the science of the nondisjunction, the mechanism, the diseases/consequences associated with nondisjuction, more than dedicating a section to "history"
• Instead of having a separate section just for illustrations, it would be ideal to integrate illustrations throughout the article, rather than just one section.
• Try to integrate the source of your information,(1, 2, 3) right after the sentence/two that you have used it for, instead of the end of the paragraph.
• Lastly, I agree with Kleina that the language for this article is a little advanced for a non-scientist reader. If I was a potential parent of a patient who had no scientific background whatsoever, I would have a hard time understanding the content.
• Overall, you have laid an impressive outline of the article, so I am excited to see the turnout of it at the end.

CarpeDiem90 (talk) 22:34, 1 April 2014 (UTC)

Thank you for your suggestions CarpeDiem90. I will update the talk page to make it less confusing for the peer reviewers. You bring up a good point about focusing on the science of non-disjunction rather than the history. Time willing, we will dedicate the appropriate efforts to both sections. We will also be looking to incorporate our illustrations into the article itself rather than dedicating a section to them. Several of your suggestions were also brought up by others and we are making those our top priority. Previte01 (talk) 02:40, 9 April 2014 (UTC)

Hi CarpeDiem90, thanks for your feedback. I have started to make modification in favor of easier readability and corrected the formatting of references. Surely, illustrations will be distributed over the whole article. Maybe we should also reduce confusion on the talk b gradually remove topics from there once they have been added to the main page. Thanks again, Wpeissner (talk) 03:13, 9 April 2014 (UTC)

The article is exceptionally well written! Great job guys!! CarpeDiem90 (talk) 01:41, 7 May 2014 (UTC)

Comments from Klortho

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.

• My biggest concern is that portions of the article seem to be verbatim copied from this source. It is possible that this is a false positive -- sometimes the copying goes the other way, and that source is actually copied from your article. If so, let me know. Otherwise, please rewrite those sections in your own words.

• I love your lead. It is the best job I have seen so far of writing at a comprehensible technical level. Good job.

• That said, this sentence seems awkward: "Three forms of nondisjunction are discerned with regard to the cell cycle phase where the segregation error occurs".

• "drosophila" should be capitalized.

• "Bridges later published his results in Science (journal) in 1914." -- Why is this notable? I don't think where or when he published is particularly important. It definitely shouldn't be in the lead.

• Which brings to mind: maybe you could consider adding a "history" section. It's up to you, but I think it would be a nice addition.

• The image is great, but you could move it up to be at the top of the article, and you could make the thumbnail bigger (maybe 400px - experiment). Also, I think you could work on the caption. The numbered list at the top isn't displaying as a list, and it makes the caption hard to figure out.

• General comment: I think you have too many very small sections, which should either have more content added to them, or be combined. I don't know how much content you are still planning on adding, but as it stands, for example, the subsection headers of "Meiotic and mitotic forms of nondisjunction" should be removed, and the section just written as one intro paragraph and three topic-specific paragraphs. On the other hand, if you're going to add more content to each, then keep them.

• In the header "Meiotic and mitotic forms of nondisjunction", you can remove "of nondisjunction". Ditto for all the other headers where you repeat the title of the article.

• As I read through it more, I do think you do need more content in the "Meiotic and mitotic forms" sections. What are the specific mechanisms of nondisjunction in each? How is the nondisjunction of one form different from another? How is it similar? Etc. I'd suggest taking the content from "Molecular mechanisms" and merging it into this section. I don't see the need to put this information into it's own special section at the end.

• Do "MI", "homologue" and "classic" refer to different types, or are they different names for the same type?

• bivalents should be wikilinked.

Good job! Keep up the good work. Klortho (talk) 19:07, 13 April 2014 (UTC)

Thank you for taking the time to thoroughly critique our article. Your ideas were helpful and have inspired us to take immediate action.

• After looking at your source, I agree that both descriptions of nondisjunction are very similar. We haven't drawn any information from that source and I'm not going to flatter myself and say that they used us as a source. We will continue to update our lead.
• Thank you for the compliment. We enjoy the challenge of taking pertinent information and making it easy to read. We will continue to do our best.
• I changed the sentence around a little bit in order to approve the flow.
• Good call on capitalizing Drosophila. Another one that I forget sometimes is Escherichia.
• I removed the last sentence of our lead. You were correct that it didn't add valuable content. I was hoping to get more information from their biographies and incorporate it into the lead.
• I love the idea of adding a history section to the article. I am sorting through a few of our sources to see if we can get enough information to make this happen. Otherwise I may add a couple more sentences to the lead.
• Great idea with the picture, I love it!
• We plan on adding more content to each section. I know it looks rough at the moment. I'm not sure if this is the best way to start an article but we're comparing it to building a house. We put down our foundation of what we would like to do. As we continue to draw from more sources we would like to fill each of these subsections up. The being said, if we can't get enough to fill them properly, we will restructure as necessary.
• Good idea on removing nondisjunction from our subheaders. We took your advice.
• Depending on how much information we can continue to gather, we may combine information from molecular mechanisms but for now I would like to keep the sections separate. If my partner feels differently we will certainly revisit this.
• MI homologue and classic are different names for the same type. I restructured the sentence a little bit to help make this distinction
• I took care of the wiki link. I'm sure there are a few more in there that need to be wiki linked. I will pull out my fine toothed comb.

Thanks again for all your help. Please keep them coming. Previte01 (talk) 03:21, 16 April 2014 (UTC)

Comments from magladem96

Hi! Your article is looking good! Here are a couple suggestions:

• Your lead is good. Easy to understand.
• Are there any additional pictures you can find to use? Maybe when you discuss the "Consequences of nondisjunction"?
• Are there other forms of nondisjunction than meiotic and mitotic? Your section heading "Meiotic and mitotic forms of nondisjunction" leads me to think there are other forms. If not, maybe re-title this section as "Three types of nondisjunction" or something similar? If so, should you mention them?
• There are a lot of diseases having to do with nondisjunction! I look forward to reading more about them as you complete this section.
• The mechanism section is interesting. Consider moving it towards the beginning of the article.
• I like the outline on the talk page. Are you planning on incorporating it or did you decide against it? I like the flow of it. Risk factors and prevention would be an interesting section, as would current research topics.
• What about adding how it was discovered? I think you mention it in the lead; is there anything additional to say about it?

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)

Hey Jen, thank you for your review. I appreciate you taking the time to offer us support and advice in making this wiki a worthwhile read.

• Thank you for the compliment on the lead. It's our hope to be able to continue to develop it even further as we are able to find more pertinent information.
• I have been having trouble finding good pictures that aren't copyrighted. I agree with you that a couple more pictures would be helpful in visualizing nondisjunction.
• Current research shows that nondisjunction can occur at two different point during meiosis. Nondisjunction can also occur during mitosis. We haven't come across any other types of nondisjuction. With that being said, I have renamed this section to "Three types." It's a working title until we can come up with a better one. Great idea!
• We are looking forward to discussing each of the diseases in depth. This will probably be the focus of my next contribution being that it's what interests me the most.
• I agree with you that the molecular mechanism section is interesting, hence I took your advice and moved it up closer to the top. Thank you!
• The outline on the talk page was a rough draft of our ambitions. Everything in there is still on the table for us to add to the main article. Currently we have quite a few subsections and are working towards adding content to them. Afterwards will will take more of what's in the talk page section and add it to the main article.
• I am looking forward to combing through the biographies of the scientists who discovered this. There is an interesting back story about how Bridges was actually a student in Morgan's biology class before they started working in the lab together. Bridge was said to have excellent eye sight and he is credited with actually noticing the physical mutations in the Drosophila which led to their combined research into nondisjunction. Depending on how much information I can muster, I may give this its own "history" section. If we don't decide to do that we will incorporate this into the lead.

Thanks again for your suggestions. I enjoyed receiving your feedback and appreciate you helping with the overall quality of our article. Cheers! Previte01 (talk) 04:13, 16 April 2014 (UTC)

Hi Jen, thanks for your valuable input. Good point about the more-than-three forms of nondisjunction. I added an introductory passage to the "forms" section, trying to make it clear that three forms is all there is, because there are also just three forms of cell divisions. I did not find any suitable (free) images, so I created one. Hope you like it. Cheers, Wpeissner (talk) 00:45, 23 April 2014 (UTC)

I like the image you created! It works really well! The image applies to Meiosis too, doesn't it? Could you rename it to make it more general and move it under the Intro of the 3 types instead of having it just under Mitosis? Thanks for taking some of my other suggestions! That's in interesting fact about the discovery! I hope you can add that section in at some point! I'll let you know if I have any more suggestions - but you're doing great so far! Jen Magladem96 (talk) 20:27, 27 April 2014 (UTC)

Hi! I noticed that you have several disambiguous terms, all involving segregation. I suggested wiki-linking to the term Chromosome segregation or sometimes not wiki-linking segregation at all, such as in the lead where you say "Both forms of cell division require the ordered distribution (segregation) of paired chromosomes or sister chromatids." I'm not sure that segregation needs to be wiki-linked there. Hope this helps! Feel free to disregard if you have other ideas.  :) Magladem96 (talk) 22:49, 5 May 2014 (UTC)

Hi Magladem96! Thanks for pointing me to this issue. I changed all those wiklinks to chromeosome segregation. Wpeissner (talk) 01:11, 7 May 2014 (UTC)

Comments from DHayes14

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 DHayes14, thanks for your great comments and suggestions! I immediately corrected the typo "segration" which of course should have read "segregation". As for the readability: this aspect has also been mentioned by other reviewers, and we will definitely work on ease of reading again. But I also think that nondisjunction is a complicated topic and that readability should not preclude presentation of advanced topics. So maybe we should go for a readability "slope": starting easy with a well explained lead section and some commonly recognized examples (e.g. Down syndrome), but also including some more advanced topics in more elaborate language towards the end of the article? Thanks, Wpeissner (talk) 21:24, 15 April 2014 (UTC)

Hi Wpeissner, I am happy that you found my comments to be helpful, tausend dank! I do think that your article is looking great and I agree that nondisjunction is a complicated topic and you and your partner are tackling it well. I like your idea of a readability "slope" and think that the article would benefit if you continued to proceed in that direction :) DHayes14 (talk) 23:15, 15 April 2014 (UTC)

Hi DHayes14, thanks for your feedback! I was trying to make the language more clear and easier to understand, sometimes also by adding additional introductions or explanations. Are there still any sections that you find particularly technical or complicated? Liebe Grüsse, Wpeissner (talk) 00:53, 23 April 2014 (UTC)

Your article, in its current state, is easy to read and doesn't appear to be overly technical. Great work! Were you planning on including any additional images, perhaps to the "Consequences" section? DHayes14 (talk) 14:11, 6 May 2014 (UTC)

Comments from Kneal0627

Hi, guys! Great job on your article thus far! Below you will find some comments/suggestions for your article:

General Comments

• The wording is unbiased, written from a neutral point of view, and easy to understand.
• Great use of wiki links throughout the article.
• Images are well placed and are relevant to the article. The descriptions are beneficial to the reader.

Introduction

• I think you have given a great introduction to nondisjunction. It's rather beneficial to the reader that you defined several terms in this section. Because you provide a wiki link for somatic cells, I don't think it's necessary to clearly define what they are; however, if you wish to do so, perhaps reword the sentence. Also, in the examples that you give, I would say "such as" rather than "like" and limit the list to two or three rather than listing several and adding etc.
• As you proceed into other sections, I think you should stay consistent with the terms used. For example, if you are going to point out that eggs are in fact called oocytes, then continue to call them oocytes throughout the article or vice versa. The same applies with sperm and segregation.
• You are careful to point out who is credited with discovering nondisjunction. I agree with Dhayes in that you may want to consider adding a Discovery section in which you briefly outline the experiments that lead to nondisjunction discovery.

Three types of nondisjunction

• The article is about nondisjunction, so you could shorten the name of this section to simply "Types."
• Also, I would suggest providing a wiki link for the term "bivalent."
• According to our ambassadors, we do not need to provide a citation back to back in the same paragraph. Rather, we can simply put the citation at the end of the paragraph. I noticed that Reference 5 was cited back to back in the Meiosis I section.
• Reference 5 is a wonderful reference, and I can understand why you use it throughout the article. It provides various definitions and images for nondisjunction. This reference gives a lot of information regarding the possible causes to aneuploidy in Meosis I as well as II. I think it is important to clarify in the article that failure of segregation in Anaphase I may occur via three ways and clearly define the mechanisms of MI, homologue, and classic nondisjunction. These mechanisms are discussed in Figure 4B as well as the text following the figure in Reference 5 Currently, the way it is written ("Failure of segregation of a bivalent in Anaphase I goes by three names:...") sounds like they are all synonyms for one mechanism of nondisjunction.
• The mitosis section could be split into two separate paragraphs rather than one long one.

Molecular mechanisms

• Perhaps you should change the title of this section to Prevention since it is discussing ways the cell inhibits nondisjunction. Initially, I thought this section was pertaining to molecular mechanisms of nondisjunction rather than prevention.
• According to Reference 11, SAC occurs in mitosis as well as meiosis; however, the mechanisms of action are slightly different for each. I think this should be clarified.

Consequences

• I don't think you need to redefine aneuploidy since it was already defined in the introduction. I like the fact that you defined the different types of aneuploidy and tied that into your discussion of the different types of syndromes. I also liked the fact that you discussed whether or not the syndromes were viable.
• Is there a typo for sex chromosome aneupoloidy? Rather than "sec chromosome," is it meant to be "sex chromosome."

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)

comments from Graeme

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 Graeme, thank you very much for the helpful comments. We will be sure to check / correct all the details you mentioned. Thanks, Wpeissner (talk) 18:00, 29 April 2014 (UTC)

Comments from Gkaltam

Hi! Your article is easy to understand and the images that you have are placed correctly and relevant to the topic. Some suggestions:

• Link bivalent in the Meiosis I section
• Meiosis, mitosis, aneuploidy, and a couple other words are linked more than once. After the initial usage and linkage, you don't have to link them anymore.
• I don't think you have to write "Three types of Nondisjunction". I believe "Types" would be sufficient enough.
• Perhaps more images should be added to the Consequences section. I think it's great that you guys listed out all of them, and how they are formed, but it does seem to be lacking some detail and/or images.
• Images pertaining to the Meiosis I and Meiosis II types of nondisjunction should be added if you have time.
• Image pertaining to the molecular mechanism may be helpful in its understanding.

Overall great job so far! Gkaltam (talk) 17:57, 27 April 2014 (UTC)

Hi Gkaltam, thanks for your input! I guess I got the main message: More images! We're working on it... Cheers, Wpeissner (talk) 18:13, 29 April 2014 (UTC)

Great progress on your article, Wpeissner!Ssumpf (talk) 01:57, 30 April 2014 (UTC)

Assessment comment

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)