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- 1 Asexual species are all haploid?
- 2 Protect This Article
- 3 Eukaryotes/Prokaryotes
- 4 Chiasma-Chromosome
- 5 The term "metaphasic"
- 6 Human Chromosomes
- 7 How do chromosome numbers change?
- 8 Chromosome Number 4 Inversion
- 9 Chromosomes in bacteria
- 10 Requests for enhancement
- 11 order
- 12 Types of chromosomes
- 13 Re Chiasma
- 14 Question
- 15 For Idiots
- 16 Just in case anyone wants it
- 17 Recent edits
- 18 Chromosome images
- 19 chromosomes
- 20 Chromosome table
- 21 I can't even find..
- 22 Full of mistakes
- 23 Chromosomes in eukaryotes: what about chloroplasts?
- 24 More Info on Structure
- 25 Uh.
- 26 Terminology for the Greater Structure
- 27 butterfly
- 28 RNA in telomeres!
- 29 Single molecule
- 30 Guinea pig chromosome number variable?
- 31 Naked DNA doth not a chromosome make
- 32 External links
- 33 Vandalism
- 34 chromosome territories
- 35 Can anyone clarify the structure of a chromatid?
- 36 Article needs SERIOUS Revamping
- 37 Person who named the chromosome
- 38 What’s a Genophore?
- 39 Mention Chromatid(s)?
- 40 And also
- 41 History: add dates
- 42 Edwards Syndrome
- 43 Second paragraph
- 44 Can someone please clarify?
- 45 Lede as of April 2015
Asexual species are all haploid?
The sentence, "Asexually reproducing species have one set of chromosomes, which is the same in all body cells," is simply incorrect. Asexually-reproducing species may be haploid (an example is Vittaria in the Appalachian Mountains), but more often they have diploid or higher ploidy levels (for instance, apomictic Boechera are almost all triploid). Paalexan (talk) 05:49, 13 October 2009 (UTC)
- Yes, quite true. That probably wasn't what the sentence was meant to imply. I've tried to clarify this. Tim Vickers (talk) 16:15, 13 October 2009 (UTC
Protect This Article
This article should be semi-protected. Over 5% of the edits are vandalism, and a lot of vandalism has been occuring recently. Jerry Zhang 00:36, 4 December 2009 (UTC)
Isn't the following line wrong?
"In eukaryotes a small circular DNA molecule may be called either a plasmid or a small chromosome."
Shouldn't it be prokaryotes instead of eukaryotes?
22.214.171.124 14:07, 4 January 2007 (UTC)
- No, eukaryotes can also have small circular cytoplasmic chromosomes. This is rare in 'typical' organisms, but is seen in more unusual species, see trypanosoma brucei for an example. - Zephyris Talk 22:54, 4 January 2007 (UTC)
- Okey, but shouldn't the page note that both eukaryotes and prokaryotes have plasmids?126.96.36.199 13:18, 16 January 2007 (UTC)
The picture points out the centromere as the connection point between the sister chromatids, but this is contradicted by the Chiasma article. Who's right? 18 July 2005
The term "metaphasic"
I work in cytogenetics and we would never use the term metaphasic. It would be understood, but very non-standard. 17:05, 31 May 2004 Rhyax
Does anyone have an updated source for the human chromosome table with the number of genes for each chromosome, with the new data trimming the genes to 20,000? - Thanks - Jerryseinfeld 12:15, 21 Oct 2004 (UTC)
Does anybody know the reason of the relative decrease of the number of genes and the bases they contain while shifting from the 1st to the 22nd chromosome? I suspect it has an explanation within the evolutionary process but a brief explanation by an experts or a link would be great. barfly 03:31, 24 May 2006 (UTC)
- Are you asking why the chromsomes are all different lengths? Or are you asking why the chromosome numbers are in the same order as their size? David D. (Talk) 03:58, 24 May 2006 (UTC)
What I tried to ask was according to this table the number of bases each chromosome contain decreases respectively.(or as you mentioned their lenght) The first chromosome contains 245,203,898 bases but the 22nd only contains 49,476,972 bases. And also the X chromosome contains approx. three times the number of bases Y chromosome contains. Does this have a biological or evolutionary explanation, or is it just a pattern? 188.8.131.52 02:05, 26 May 2006 (UTC)
- The numbers of the chromosomes were assigned in the order of their size, so by definition they should decrease in size. The X and Y size difference does have an evolutionary significance. There is good evidence that they were once the same chromosme but the Y is slowly getting deleted over time. See the following: Y_chromosome#Origins. David D. (Talk) 15:35, 26 May 2006 (UTC)
How do chromosome numbers change?
I'm currently in a debate about evolution on a forum. Somebody said that mutations are always negative, and I argued that they're not, and then this somebody brought up Down syndrome. I pointed out that Down syndrome is not the cause of a mutation, but trisomy -- having the wrong number of a chromosome. My interlocutor said, yes, that's true, but how do different creatures have different number of chromosomes then, when they all come from common ancestors? While I don't think trisomy is the answer, this does seem a bit tricky. Anybody know? - Furrykef 07:22, 28 Oct 2004 (UTC)
- Down's Syndrome occurs when errors happen in MEIOSIS cell division for the egg. During meiosis, normally an egg will have 23 chromosomes each (in humans). But in some occations, 1 egg receives 22, the other 24. The egg with 22 becomes sterile. And if the egg with 24 becomes fertilised, the zygote will have 47 chromosomes (23 from sperm), the baby will be Down's Syndrome. jynx
- I also came here looking for an answer to a similar question. Is Downs a step in the process that produces a new species ? Is there any solid body of knowledge or research about this Question ? I know that normally chromosomes come in pairs and people with downs have a single extra chromosome. I assume they must produce 23 chromosome gamates and 24 chromosome gamates. Assuming two people with downs have children would there be a one in four chance that their ofspring would have 24 pairs of chromosomes and a one in four chance that their offspring had 22 chromosome ? Martin Spamer
- Ploidy occurs in this manner: A cell undergoing mitosis (or the first stage of meiosis, which is the same as mitosis) copies its chromosomes normally, but then it fails to fission to produce two cells (Cytokinesis). Thus, there is now one cell with double the number of chromosomes. If this was a germ cell undergoing meiosis, the offspring of that cell will have an extra chromosome too. Cytokinesis can be inhibited with certain chamicals.
- Needless to say, the fact that a detrimental mutation such as Down's exists, does not prove that mutations are harmful.184.108.40.206 17:34, 14 August 2007 (UTC)
- Down's syndrome isn't a mutation in the sense that mutations are DNA copying errors. Down's syndrome is a mechanical failure to segregate the chromosomes properly during meiosis. It is not a valid analogy to mutations that cause speciation, which will invariably cause changes to the structure of proteins produced by the transcription of genes and/or the contextual expression of genes. These can affect the development or functioning of organisms in ways which can certainly be beneficial depending on the context of the whole organism. Aneuploidy is vanishingly unlikely to be beneficial because it grossly affects a vast number of genetic systems which depend on there being a certain number of chromosomes present to ensure the right amount of gene transcription. It is a bad example of a "mutation" in an evolutionary context, however, and in a debate on evolution is thrown in at best in ignorance and as worse as an attempt at misdirection. --220.127.116.11 13:47, 3 November 2007 (UTC)
- Down's Syndrome and the like are irrelevant in chromosome number change. Changes in the number of chromosomes is caused not by the addition or loss of any genes, but simply rearranging the genes. Mostly through fusion of two chromosomes or through the splitting of a single chromosome. For example, chromosome 2 in humans can be seen to be nearly identical to chromosomes 2A and 2B in chimpanzees and the other great apes, but fused into a single entity. For more information on this, this page is a great explanation. Nik42 (talk) 05:04, 15 December 2008 (UTC)
Chromosome Number 4 Inversion
Could anyone advise on further info on this subject.
I have looked at Wolfs Syndrome, but this is a shorten of one of the arms.
My son has this and I'm looking for more answers.
Chromosomes in bacteria
The "Chromosomes in bacteria" section states
- Bacterial chromosomes initiate replication and one origin of replication.
This does not make sense for me. Is this by chance supposed to read "... initiate replication at one origin ..."? --Jochen 11:56, 18 Mar 2005 (UTC)
Requests for enhancement
Sorry if this isn't the right place, but I can't find a molecular biology or genetics wikiproject. As a layman, I've found a few things missing from our coverage of molecular biology (maybe they're there, I just can't find 'em):
- a lot of the genes listed in list of notable genes refer to the locus of the gene, but locus points to a disambig page. I think we should make an article called something like genetic locus or chromosomal locus (or whatever is appropriate) into which most of that disambig line goes, and which explains better the 11q23.1 type notation (ideally with one of the band diagrams, as in ).
- equally, if there is a separate addressing scheme for genes in mitochondria or on plasmids, we should have that in, or linked from, the genetic locus article too.
- and a note or two about how the addressing scheme holds, or changes, for non-human animals
- ideally an entry about those chromosomal bands, and a link from the disambig page band
- is it possible to construct a template like the various geographical-area ones (like Template:gbmapping or Template:Mapit-US-cityscale) which we could use to link to public genetic databases (like http://genome.ucsc.edu/cgi-bin/hgTracks?position=11q23&pix=840&Submit=Submit&db=hg17)
- in general, there doesn't seem to me much at wikipedia that would allow me to make much sense of the type(s) of diagrams used in bioinformatics (like the human genome one above). I realise that one would need a proper qualification to make real use of the diagram, but I think the wikipedia could reasonably contain an article about the diagram type and a dumbed-down explanation of what's on it, what it can and cannot show, and for what applications one would use it.
Table 1: Examples of chromosome numbers (diploid).
- Are these in any order? chromosome number order would seem best to me. - Omegatron 14:12, May 29, 2005 (UTC)
Types of chromosomes
I feel this article needs to address the different types of chromosomes, i.e. metacentric, submetacentric and acrocentric. A search for 'acrocentric' yields no definition of this term, which is a pity, because it is important to know what an acrocentric chromosome is when talking about Robertsonian translocations.
As I understand the processes, sister chromatids are joined at the centromere in cells undergoing or about to undergo Mitosis and Meiosis. Chiasma is a crossing over of one part of one arm from one chromatid to another arm of a different (non-sister) chromatid thus producing a completely 'new' form of the two original (and different) chromosomes as well as a 'copy' of each of the original chromosomes in the resultant divided cells.
see http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookmeiosis.html under Prophase 1
Hope that helps
It´s written: "A chromosome is a singular piece of DNA". But, if DNA is just ONE molecule, how is it possible that a chromossome is a piece of it? If a molecule is broken into 2 parts, one gets TWO molecules, and not TWO PIECES of a molecule. Does the entire DNA molecule exist somewhere, so that one can say that a chromossome is just a piece of it? Or, if a cell has 22 chromossomes it means that it has 22 different molécules (DNA1, DNA2 etc)? --18.104.22.168 (talk) 12:29, 31 October 2008 (UTC)
- Each piece of DNA contains two strands (two molecules) in a double helix. A piece of DNA can therefore be pulled apart into two pieces. These two strands are copies of each other. Therefore if you have 22 chromosomes, you have 22 pieces of DNA but 2 copies of each - 44 molecules in total. See introduction to genetics for more. Tim Vickers (talk) 16:37, 31 October 2008 (UTC)
Can someone write a section on chromosomes for idiots? the above is too tricky to understand for someone who has no idea what is going on.
- It's amazing to the layman to read these scientific articles where it's all so obvious to the editors with their backgounds but totally mystifying to the rest. I come from a military background and the military folks do the same thing. SimonATL 19:58, 15 June 2006 (UTC)
- I'd say the introduction needs to be rewritten for everyone (including biologists) not just idiots. There is massive amounts of terminology and discussion in the introduction that does not even appear in the article! For example, histones, mitosis, p arm and q arm, kinetochore, tubulin are all in the introduction. Even the alpha and beta subunits of tubulin, with respect to the microtubules/kinetochore interaction, are mention but absolutely NOTHING in the article. It's supposed to be a summary of the article. The current introduction needs to be scraped (some of it could be incorporated in to the main text) and we should start from the ground up. David D. (Talk) 20:23, 15 June 2006 (UTC)
I agree. I am curious as to how DNA is translated into construction. It's been said in this article, and in very school, that DNA is the body's blueprint. But how does DNA actually get things built in the human body? That to me is very interesting. —Preceding unsigned comment added by 22.214.171.124 (talk) 10:44, 15 December 2007 (UTC)
Chromosome is unwound, sections of the DNA are 'transcribed' by RNA polymerase, the 'RNA' produced is then 'translated' by ribosomes into protein strands encoded by 3-base 'chunks' of RNA. —Preceding unsigned comment added by Apothecia (talk • contribs) 08:08, 8 April 2009 (UTC)
Just in case anyone wants it
The recent edits by unregistered users seem to have removed a lot of useful content from the page. I suggest a reversion to this version, which will put back all the information. I, for one, like the picture... -- Tuvok^Talk|Desk|Contribs 05:00, 30 November 2006 (UTC)
- Actually, I've just reverted to the old version. Let me know on my talk page if I shouldn't have done this. Since there was no discussion about taking this information out of the article on this page, and the edits were extensive by an unregistered editor, removing useful information, I feel no problem. Again, let me know if this is wrong. -- Tuvok^Talk|Desk|Contribs 05:06, 30 November 2006 (UTC)
VANDALISM. Please revert to older versions!!!!
Dear all, I have recently refurbished the Chromosome article in the German Wikipedia. In the process, I have uploaded several images you might want to make use of also for the English article. All of them are on Commons, including an English legend. For an overview over these images, either have a look at the German aricle or at the gallery on my user site on commons here. If there are details you wish to discuss with me, please do it at my discussion site at the German Wikipedia which I check much more often than the one on commons or on the English site. edit is "Seite Bearbeiten", preview is "Vorschau" and save page is "Seite speichern" --Dietzel65 19:09, 20 December 2006 (UTC)
- That depends on the organism. Human has 46 chromosomes. However cat has 38, sheep has 54, dog has 78 etc. (Copsi 18:25, 25 April 2007 (UTC))
As i was trying to cite a few things on the table showing the amount of chromosomes per species of animal, iaccidently screwed up the chartFatdelear 22:38, 6 February 2007 (UTC)
- I did the same thing when I added the ref for dog. You forgot to close the ref tags, that's all. Easy mistake. And FYI, you don't need to put brackets around the ref text. Hope this helps you avoid the same mistake next time! — Tuvok[T@lk/Improve me] 22:59, 6 February 2007 (UTC)
I can't even find..
I read over most of the page, and I can't seem to find the real function of chromosomes. It tells everything about them, but not what they do. It's like the wiki page for cars saying what kind of engine one might have, that it has 6 windows, that it seats 8, and not even mentioning it's a method of transportation. Let me know on My talk page if you can help me. Thanks, Ard0 (Talk - Contribs) 18:17, 23 February 2007 (UTC)
Full of mistakes
This article is full of mistakes,it has to be renewed also.Some of the pictures are old.But the biggest mistake is in the first lines saying: there is circular DNA in eukaryotic cells.It has to be removed immediatly, it will lead other people to confusion. Doctor
- The mitochondrial genome, as found in the vast majority of eukaryotic cells, is almost universally circular. - Zephyris Talk 01:54, 17 March 2007 (UTC)
Also, in the Historic section the term Genetic Load is being used in lieu of Genetic content or Genotype. If the term was originally used for meaning 'genotype' by Roux it should be cleared up, because of the modern meaning of Genetic Load.Bigfootpegrande (talk) 10:15, 27 September 2011 (UTC)bigfootpegrande
Chromosomes in eukaryotes: what about chloroplasts?
The wording suggests that that only chromosomes in eukaryotes are nuclear, mitochondrial and some (relatively ill-defined) cytoplasmic chromosomes. It doesn't actually say that these are the only chromosomes, but a reader might reasonably expect such a list to be complete! Shouldn't chloroplast chromosomes be included somewhere in this list as all(?) photosynthesising eukaryotes have them? SamTheCentipede 11:40, 22 June 2007 (UTC)
More Info on Structure
This article should have more information added on the structure of the chromosome. It now only bluntly exhibits two lines describing the structure in sequences, yet not the actual structure of the chromosome itself.--Yowizman 21:26, 18 June 2007 (UTC)
Terminology for the Greater Structure
Is there a term for the structure consisting of all the chromosomes together? For example, we say: "humans have 23 chromosomes." What is the structure comprising the 23 chromosomes called? e.g. "the human _______ consists of 23 chromosomes." Is "genome" the word I'm looking for?126.96.36.199 17:34, 14 August 2007 (UTC)
The table gave the chromosome number for butterflies as 380, and someone had marked it with a fact template. Google searching seems to show many counterexamples, e.g., http://www.fmnh.helsinki.fi/english/zoology/entomology/research/ithomiinae/index.htm --188.8.131.52 04:32, 28 August 2007 (UTC)
RNA in telomeres!
Check the Telomere talk page; I left a note there about fascinating new research that seems to show that telomeres contain RNA as well as DNA. Unfortunately I don't have time to check it out properly and include it in the article. --Slashme 08:13, 8 October 2007 (UTC)
A double helix of DNA contains two molecules of DNA associated through hydrogen bonds. I've therefore reworded the piece in the lead about chromosomes only containing a single molecule of DNA. Tim Vickers (talk) 22:57, 18 November 2007 (UTC)
Guinea pig chromosome number variable?
I found the following ref which claims that the guinea pig has 62 ± 2 chromosomes. It was published in 1928, but looks like good work. Any comments?
- I think it was pretty common then to be unsure of the exact number, especially with such a high number of chromosomes. or are the specifically saying it varies in different animals? Consider the history for the recorded number of human chromosomes:
- In 1892, Hansemann and Bardeleben estimated in the order of 23-24.
- In 1912, Hans de Winiwarter, counted 47 chromosomes, 46 chromosomes and 49 chromosomes. He proposd the correct number of male chromosomes was 47
- In 1921, Theophilus Shickel Painter, correctly reported the chromosome number as 46, but in a follow up paper he changed that to 48.
- 48 human chromosomes was the accepted value until 1956 when Joe-Hin Tjio and Albert Levan reported the correct value as 46.
- As you can see there was a lot of uncertainty in these types of measures. David D. (Talk) 08:56, 3 December 2007 (UTC)
OK, that makes sense. --Slashme 13:12, 3 December 2007 (UTC)
Naked DNA doth not a chromosome make
The term chromosome includes the whole shbang, including histones, centromere, the works. That's the whole point of the term. If you use it merely as a synonym for DNA, you are definitely misusing the term, and also creating confusion amongst the readers. The evolution from prokaryotes to eukaryotes is probably the second greatest evolutionary advance; in addition to fusing two or more prokaryote forms, some structures are new to eukaryotes! Chromosomes are an excellent example of this. Macdonald-ross (talk) 19:31, 11 December 2007 (UTC)
External links on Wikipedia are supposed to be "encyclopedic in nature" and useful to a worldwide audience. Please read the external links policy (and perhaps the specific rules for medicine-related articles) before adding more external links.
The following kinds of links are inappropriate:
- Online discussion groups or chat forums
- Personal webpages and blogs
- Multiple links to the same website
- Fundraising events or groups
- Websites that are recruiting for clinical trials
- Websites that are selling things (e.g., books or memberships)
I realize that some links are helpful to certain users, but they still do not comply with Wikipedia policy, and therefore must not be included in the article. WhatamIdoing (talk) 06:29, 17 January 2008 (UTC)
I have uploaded this picture about chromosome territories to which there is no page, yet. (the image is messed up (fonts), but I have asked why does that happen and will get it fixed when I get a reply). --Squidonius (talk) 11:55, 12 April 2008 (UTC)
- As I understand it, it happens because Wikipedia doesn't have the font you used when you created the SVG. Let me know what solution someone recommends, I'd like to hear it, since I've had the same problem. Madeleine ✉ ✍ 13:27, 12 April 2008 (UTC)
- I used the "Bitstream Vera Serif" font following some advice I read that Wikipedia has that font. My one effort was commons:File:Hardy-Weinberg.svg (although I saved it from Inkscape as "plain SVG" due to my uncertainty about the best format). That font is freely available on several platforms. You can use any font, provided you convert "Object to path" (big problem: no one can edit the text, because it has been converted to a graphic). Johnuniq (talk) 07:51, 8 April 2009 (UTC)
Can anyone clarify the structure of a chromatid?
I've never been able to figure out whether the long and short arms of one chromatid lay diagonally across the centromere or whether each were on one side of it... 184.108.40.206 (talk) 19:46, 31 May 2009 (UTC)
Article needs SERIOUS Revamping
A cursory look over this Wikipedia article shows a number of glaring omissions, as well as very poor organization. The introduction is far too long and much too specific; there is no need to discuss mitosis and meiosis in the introduction to what a chromosome is; that type of information should be found in a more specific subsection. The entire last paragraph reads like it was written by someone who wants to put forward an idea into the debate on what a chromosome is defined as, and should be removed.
As for the subsections, the history section is written in a very "emotional" prose, for a lack of a better word. A more academic recounting of the history of the chromosomal theory of inheritance would be nice. For the part with "Morgan's Lab", perhaps it would be prudent to mention that what they did was map the white-eye gene to the X-chromosome using both genetics and microscopy.
The entire structure of the article is not well designed. As there are more differences between prokaryotic and eukaryotic chromosomes than they tend to have in common, it would be better to split up sections into descriptions, such as structure, behaviour in mitosis, and then subdivide those sections into the difference between euks and prots. Right now, it is very hard to ascertain from the article what are the key differences between eukaryotic chromosomes and prokaryotic ones. Hell, the world "telomere" isn't even in the article! Also, the DNA packaging image is in the wrong section! That shows eukaryotic packaging, and should mention that the actual structures have not been solved for 30 nm fiber or greater.
There is no section about different forms of sex determination using sex chromosomes, at best a simple part about XX/XY in humans.
There should be a section briefly addressing the concept of a genome and genome sequencing, and redirecting to articles concerned with it.
Terminology needs to be addressed. Be very careful using the word "piece" of DNA (what the hell is a "piece" of DNA) or strand (need to be sure no ambiguity between single and double stranded DNA).
I would be making these edits myself, but I know without some sort of consensus or approval, they will be removed.
- I agree, the organization is pretty much a grab bag, and there is a lot of superfluous stuff, as well as important material that's missing. Why don't you suggest an outline for a new version here? Then we can take it from there. Agathman (talk) 15:22, 25 January 2010 (UTC)
- I would suggest making the following sections -
- History (discuss origin of term, and key experiments to determine that chromosomes were responsible for heredity, and how genes, the functional units of genetics, were ultimately ::found to be on chromosomes (i.e. tracking of white-eyed mutation on the fruit fly X-chromosome by combining genetics and microscopy).
- Structure (divide into prok and euk here. Discuss centromeres, telomeres, and chromatin packaging, distinguish between light compaction i.e. euchromatin, and heavy compaction i.e. heterochromatin and mention role of histones. Put that nice image of the different levels of compaction here. Good place to touch on chromosome territories. Briefly relate compaction to gene expression. Also, good place to touch on evidence for endosymbiosis theory of mitochondria and chloroplasts, unless a chromosome evolution section is wanted)
- Cell Division (Need to subdivide this into Chromosome replication in S-phase, then chromosome behavior in mitosis versus meiosis. No need to go into too much detail here, as one can link to the full length articles concerning these subjects)
- Sex chromosomes (distinguish between autosomal chromosomes and sex chromosomes, and show the different systems i.e. XX/XY in mammals, ZZ/ZW in reptiles and birds, XX/X0 in worms).
- Genomes (discuss variation of number of chromosomes between different species. Mention gene number versus DNA size i.e. C-number paradox.
- Human genetics (put stuff here specific to human genome, such as human karyotype, gene density versus chromosome length, and diseases related to aneuploidy, such as Down's syndrome or the relationship to cancer)
- Summary of key differences between prokaryotic and eukaryotic chromosomes (self-explanatory, but I think this is useful for anyone who wants to quickly learn what the differences are)
- I would suggest making the following sections -
- That's off the top of my head. If others have good suggestions for other sections, I'm all for it. However, as this is wikipedia, I feel that a general biological concept such as a chromosome should not get too specific and rather refer the reader to articles that are more specific (i.e. chromatin compaction, DNA replication, gory details of mitosis, etc). I read a lot of the complaints on the discussion is that the article is too difficult to understand if one lacks a solid biology background. 220.127.116.11 (talk) 19:56, 26 January 2010 (UTC)
- Sounds good. I've made a sandbox for it as a subpage from my user page, and I recommend we try to build the page there and then get consensus to substitute it for the current one when it's ready. See sandbox at User:Agathman/Chromosome
Person who named the chromosome
What’s a Genophore?
Is there a reference for the origin of this term? I’m in expert in bacterial genetics and have never seen this term before. Lol. Nor does there seem to be any need for it. The WikiDefinition of “Chromosome” is “an organized building of DNA and protein that is found in cells”. This definition is appropriately applicable to the DNA complexes in all cells: bacteria, archaea, and eukarya alike. Jragon (talk) 00:19, 27 September 2010 (UTC)
I was doing some homework for biology, and it occurred to me in the process of researching that it might be nice to include a brief mention of what a chromatid is in the overview section, linked to the respective article. In fact, as the chromatid article is very short (no more than half a dozen paragraphs) it might even be plausible to merge it into this article and create a redirect. I'm going to refrain from making any changes myself because I'm no expert on why things are where and don't want to make an idiot of myself screwing around with the status quo. I just thought it would be nice for people to have a really brief definition of the term, as vocabulary (while taken for granted) is often one of the most difficult things to learn for any amateur. Bronsonboy (talk) 01:22, 8 February 2011 (UTC)
Would someone clarify the distincution between "chromatid" and "chromasome" as here: Second sentence "It [the chromosome] is a single piece of coiled DNA containing many genes," Surely the chromosome (as in the diagram) is a pair of chromatids and is therefore two pieces of coiled DNA! Drmikec (talk) 16:01, 6 April 2011 (UTC)
History: add dates
The article states that those who survive their first year can live healthy afterwards. There is no source for that, and information in the Edwards Syndrome's wiki article does not back it up, actually quite the contrary. Frohfroh (talk) 18:41, 27 April 2012 (UTC)
Anyone know what its trying to say? I know it needs work and would be glad to do it, but am not a domain expert and it is not obvious what it was trying to say (bold are where I have some trouble, italic where I have a question):
- Chromosomes vary widely between three and two types of organisms, from mammals to reptiles. The DNA molecule is circular and linear at the same time, and can be composed of 123,235 to 13,234,3454,246 nucleotides in a long chain. Typically, eukaryotic cells (cells with nuclei) have linear chromosomes (I thought they were linear and circular at the same time - john) and prokaryotic cells (cells without defined nuclei) have circular chromosomes. Also, cells may contain more than one type of chromosome; for example, mitochondria in most eukaryotes and chloroplasts in plants have their own chromosomes.
Can someone please clarify?
They way I understand it, a chromosome is not composed of two sister chromatids.
The two sister chromatids are more like two identical chromosomes formed after replication of one chromosome.
Could someone please confirm this?
If true then the following only confuses the reader into believing that a chromosome is composed of two sister chromatids.
"Diagram of a replicated and condensed metaphase eukaryotic chromosome. (1) Chromatid – one of the two identical parts of the chromosome after S phase. (2) Centromere – the point where the two chromatids touch, and where the microtubules attach. (3) Short arm. (4) Long arm." — Preceding unsigned comment added by 18.104.22.168 (talk) 15:41, 5 January 2014 (UTC)
- You're right, it is confusing and at moments contradictory within the text. To clarify, a chromatin is the uncondensed unorganized DNA that exists during interphase. A chromosome is a super condensed highly organized DNA that exists throughout mitosis and cytokinesis. A chromatid is one half of a mitotic chromosome. Now, a chromosome can contain ONE or TWO chromatids depending on the stage of mitosis. During prophase and metaphase the chromatids are bound together forming an "X"-like chromosome. During anaphase and after, the chromatids are separated and they equate a chromosomal unit with a "<" or ">"-like form. Therefore you have 92 chromosomes during the brief final periods of mitosis. --Spmoura (talk) 05:12, 24 January 2014 (UTC)
Lede as of April 2015
The lede is pretty lousy. Prime example:"In the case of archaea by homologs to eukaryotic histones, in the case of bacteria by histone-like proteins." Here is a hint: Capitalizing the first word of a phrase and ending the phrase with a period (full stop) does NOT magically create a (correct English) sentence. The above example also lamely says something about homologs (noun) in the prepositionary phrase "by homologs", I'd guess that these "homologs" actually have a name, and that anyone coming to this article needing information at this level (introductory) will NOT KNOW WTF a "eukaryotic histone" is. I also question the claim that histone homologs or histone-like proteins "pack" the chromosome. (The link to "histone-like proteins" should be removed until that stub contains useful information, as of now it does not).) The same blunder/confusion occurs in the lede of the Histone article. In order for a histone to "pack" or "package" DNA, it should be an (active) agent. Acting as a substrate on which the DNA arranges itself in a compact form is not "packing" it. (Many protein assemblies actively assist in various metabolic and reproductive functions, whereas the histone is simply a 'cradle' which provides the place for the DNA coil to compactly set.) Other examples of why I think this is poorly written and not very useful are:
1."A chromosome is a packaged and organized structure containing most of the DNA of a living organism." WRONG. The SET of chromosomes in a living organism contain "most of the DNA". (Except, is this right?)My point here is that one chromosome may or may not be "most of" a cell's DNA, and that many cells have a dozen or more chromosomes, and therefore there is no one which is "most of" the DNA).)
2."It is not usually found on its own..." Really?? Who wrote this?! You mean not found without surrounding molecules (such as water)?? What a useless thing to say. ANYTHING IN A CELL IS NOT "found on its own", by definition. Wow. I suppose the author meant "exists independently in solution". The sentence goes on, turning into a ramble about histones and transcription factors which are "usually" found with the chromosome except when they are not. More babble. I'm no microbiologist, but it might be useful to point out that in a metabolically active cell, a chromosome is (almost always?) being accessed for transcription at some locations and packed onto some histones at (most?) other locations. An analogy might be useful here (to say Amazon's web pages or to a restaurant's chairs (at any one time only some are being used, many are "packed" in close to the tables).
3. The rubbish about whether its visible or not should be removed from the lede and repositioned somewhere else; visibility is hardly important enough to merit the kind of treatment its given in the lede.(Might be useful to point out why most microphotographs show a chromosome in the classic figure-8 state).
4. The lede should answer the following: What?, why?, where?, and who and when?. Perhaps "how?" should be explained later in the article. What it is: it is the main way a cell's DNA is structured. Why: because this structure allows it to function as needed in the cell, including reproduction and transcription, while minimizing its 'footprint'. Where: depending on domain (eukaryote or not) its found in the nucleus (eukaryotes) or floating in the cytoplasm (Archaea and Bacteria). Who and when: although known as cell components by the mid-1800's, their function was first understood in the early 1900's by Boveri and Sutton (see Boveri-Sutton Theory).22.214.171.124 (talk) 13:36, 9 April 2015 (UTC)