Talk:Chromosome

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[edit] Chiasma-Chromosome

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

[edit] The term "metaphasic"

Why not use the more conventional term "metaphase chromosome"? JWSchmidt 15:58, 31 Mar 2004 (UTC)

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

[edit] Human Chromosomes

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? 85.101.173.125 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)

[edit] 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.

[edit] Chromosome Number 4 Inversion

Could anyone advise on furthur info on this subject.

I have looked a tWolfs Syndrome, but this is a shorten of one of the arms.

My son has this and I amlooking for more answers.

Peter

[edit] 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)

[edit] 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 [1]).
  • • I've split it out into Locus (genetics) --Arcadian 17:09, 5 October 2005 (UTC)
  • 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.

So we already have these somewhere, and if not, should we? -- John Fader (talk | contribs) 15:50, 23 Mar 2005 (UTC)

[edit] order

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)

[edit] 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.

[edit] Re Chiasma

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

[edit] For Idiots

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)

[edit] Just in case anyone wants it

Figure 1: 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.

The old chromosome image... - Zephyris _Talk 21:47, 25 November 2006 (UTC)

[edit] Recent edits

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)

Seems fine to me! there was a lot of relevant and useful info in the stuff which was removed - Zephyris _Talk 11:12, 4 December 2006 (UTC)

VANDALISM. Please revert to older versions!!!!