Talk:Twin

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What are the causes of identical twins and non identical twins? I dont know do you?

Someone please write a paragraph about criminality and penal code with regards to twins. Ex: if CCTV footage shows a person committing murder while lying in wait, and he/she is one of identical twins and they refuse to confess, do both of them get sent to the gas chamber? Issues like this are very popular in crime fiction stories and movies. Also, there was a recent news story about brazilian twins, who both sat in prison for drug trafficking, but one got released instead of the other due to tricking and bribe. He got caught and now both will have to serve some extra years for obstructing the way of justice.

It would be interesting to do some research and figure out how much of this stuff actually happens in real life. (I am reminded of a story arc on Without a Trace in which one identical twin tricks his brother into acftually confessing a crime.) The use of twins in mystery stories is worth talking about in and of itself. (Notice that I'm not volunteering.) -Aranel ("Sarah") 00:05, 14 July 2005 (UTC)

Contents 1 Identical twins not the same gender? 2 Foetus in foeto 3 Singleton 4 Congratulations, lady, but... 5 Half-identical Twins 6 Olsen twins? Who needs them? 7 Discpreancy between this entry and the entry on Conjoined twins 8 Every Other Generation Discrepensy 9 oral contraceptives 10 Non-sibling twins? 11 Predisposition for monozygotic twinning 12 Recent large additions 13 The removed section on twins in fiction 14 The Olsens 15 Polar body twins (identical-fraternal twins) 16 "Famous Twins" list 17 private language 18 discrepancy in describing twinning rates 19 duration of pregnancy 20 Maury??? 21 Ethnicity and twins 22 Need a better picture 23 Twins and Society 24 Semi-Identical

[edit] Identical twins not the same gender?

The article has this line:

Monozygotic twins are genetically identical unless there has been a mutation in development; they are only usually, but not necessarily, the same gender.

Could someone provide a refrence for this, it seems rather unbealievable, or seems like something that would require a very specific mutation in one of the twins, and thus exceedingly rare. If true, it needs more of an explination than the simple statment given. When such a thign happens are there other medical considerations? How rare is it? Is it even common enough to be called out in the article without saying that it is exceedingly rare? Dalf | Talk 18:22, 16 May 2005 (UTC)

well, although it is very rare, monozygotic twins may be of different genders when an egg containing the abnormal chromosome, xxy, splits into two. Then, one half of the egg is xx, a girl, and the other half is xy, a boy. Otherwise, they still share identical DNA, they just are of opposite genders.

Oops the next paragraph addresses this. Dalf | Talk 18:23, 16 May 2005 (UTC)

read Intersexual 4.250.198.126 19:00, 16 May 2005 (UTC)

I dramtically reduced the amount of text on identical twins not the same gender and removed the section header. It's not a relevant risk of having twins, and so its a nonsequiteur to spend an entire section and two paragraph on the phenomenon. From the sources I've seen, only 3 cases have ever been documented (not "3 in 100,000" or "3 in 1 million" or "3 in 2.5 billion" but just "3". Ever.) To put that into context, you have a greater chance of personally meeting and then going skydiving with conjoined twins than of having different-gendered monozygotic multiples. I do belatedly agree with Violetriga that the Intersexual article isn't directly on point -- I left that in in my initial edit to try to provide context for the description of the mono-multiple gendered process that I felt didn't belong here. I'd be open to putting in a wikilink to a different article that provides that context, but it really doesn't belong here. Any suggestions for where to link to? Nandesuka 10:48, 17 May 2005 (UTC)

Well, identical twin and identical twins redirect here: how about Mixed sex identical twins? -- ALoan (Talk) 11:41, 17 May 2005 (UTC)

That makes a lot of sense to me. We could even take the text I elided regarding XY / XO chromosomes and turn that into the stub of that article. Violetriga, is that OK with you? Do we have consensus? -- Nandesuka 14:02, 17 May 2005 (UTC)

Sorry about the belated response - for some reason I hadn't noticed this discussion. I think the information should certainly be somewhere and I'm not entirely sure that it is worthy of its own stub, hence my preference for inclusion here. If you want to try it and see how well it works then by all means go for it - it may work well. violet/riga (t) 09:49, 2 Jun 2005 (UTC)

I agree that this is rare, but XX/XY hermaphroditism is uncommon; if you superimpose monozygous twinning on that frequency you can get the potential frequency of this event. How relevant? I believe the article generally ok in this regard. It is a curiosity, but one that reminds us that biology is full of rules that can be broken.

"Although their traits and physical appearances are not exactly the same due to environmental conditions in both the womb and outside the womb, they do have the same DNA... Monozygotic twins are genetically identical (unless there has been a mutation in development) and they are the same gender. (On extremely rare occasions, an original XXY zygote may form monozygotic boy/girl twins by dropping the Y chromosome for one twin and the extra X chromosome for the other.)"

The above says that identical twins have the same DNA, but on rare occasions different chromosomes. Doesn't that contradict? Surely it should say that most are genetically identical, but not all? this seems to suggest that identical twins don't necessarily have the same DNA, and can in fact be "profoundly different". What's the truth? Are the genetic differences limited to a potential XXY chromosome as suggested above?

[edit] Foetus in foeto

"Doctors in Bangladesh say they have removed a long-dead foetus from the abdomen of a teenage boy who was complaining of stomach pains. [...] The condition is known as "foetus in foeto", or inclusion twin." (June 2005 BBC article) Google tests for either term (in quotes) yields less than 15 results. "Fetus in Feto" yields about 30 hits, some being non-english pages. Anybody know anything about this? Are the terms wrong? --Nectarflowed ^T 03:05, 27 Jun 2005 (UTC)

Yes, it's a real phenomenon. There are some researchers who would suggest that a much higher percentage of people than we realize (maybe even a majority) start out as a twin, but the other twin is soon absorbed. (But no, I can't cite references, and I don't know the actual term. There usually isn't going to be a recognizable trace of the non-surviving twin in the sibling's body, though.) -Aranel ("Sarah") 23:57, 13 July 2005 (UTC)

And, hey, this is already mentioned in the article. See parasitic twin (the extreme case) and vanishing twin. -Aranel ("Sarah") 23:58, 13 July 2005 (UTC)

[edit] Singleton

Are you sure this is the correct word? I have never heard it outside of Sex and the City. Trollderella 20:17, 17 October 2005 (UTC)

• Yes - that's the correct term. violet/riga (t) 21:32, 17 October 2005 (UTC)

It may have been an abdominal pregnancy that died "in abdomino" and then became a scarred fibrotic remnant. These cases are as rare as siamese twins. Often these pregnancies lead to horrid complications. Not related to twinning.

[edit] Congratulations, lady, but...

The image of the woman 'pregnant with twins' is totally out of context for this page. It simply doesn't contribute at all to the subject of the page. I feel a little bit sorry for the girl (and the twins aboard), but this simply isn't the place for that picture. Goodbye and good luck, you three! :) Kreachure 00:53, 4 November 2005 (UTC)

Erm, why does it not contribute? There's a long discussion of twin pregnancy issues on this page - it looks relevant to me. Trollderella 20:23, 4 November 2005 (UTC)

Because the article is primarily about twins, not future mothers of twin, and it smacks of vanity. For the record, I'd have no objection to that picture going on the pregnancy page. Nandesuka 13:44, 6 November 2005 (UTC)

I agree that it's not particularly relevant here. It's a picture of a pregnant woman. The caption says she's pregnant with twins, but that's not something you can know from a photograph. Friday (talk) 15:13, 6 November 2005 (UTC)

Well, fine, I'm not going to labor the point (ha ha!), but the article does devote significant space to the notion of being future mothers of twins. Trollderella 16:25, 7 November 2005 (UTC)

[edit] Half-identical Twins

There seems to be a twin phenomenon not listed on this page: Polar Body Twins (AKA half-identical twins). Appearently they occur when a single egg splits into two parts, both of which are subsequently fertilized. I guess it's just theory at this point (hard to prove with current genetic testing), but maybe it should be up here.

See the section above labeled "semi-identical twins." The phenomenon does not exist except in people's minds. An unfertilized zygote can not split by itself, and if it could it would not still be able to be fertilized. Nandesuka 13:50, 12 November 2005 (UTC)

(I was the first speaker) I did some more looking, and found some more info. Appearently all eggs split before fertilization, resulting in one strong gamete and another weaker one called a Polar Body which just degenerates. The theory is that sometimes, both the egg and the polar body survive, and become fertilized.--Tychomonger 22:32, 12 November 2005 (UTC)

You'll need to cite a reputable medical source for this. We looked into it sometime this past summer on this talk page and did not find any credible sources. Nandesuka 11:51, 16 November 2005 (UTC)

I have never seen any medical citation for this. In addition, if you have two eggs, there is no way you could distinguish this from fraternal twinning, unless you were compulsive enough to notice that fraternal twins differ for every single maternal allele. ~

[edit] Olsen twins? Who needs them?

Excuse me for being old-fashioned, but why do we need a publicity photo of some second-rate Hollywood celebs on what is otherwise a reasnably well written article. Delet the pic! --Hugh2414 17:50, 3 December 2005 (UTC)

I agree mainly because they look so much alike. If there's an image used as a prime example of fraternal twins, wouldn't a pair that can't easily be mistaken for identical twins be better? Coyotecoyote 11:19, 11 December 2005 (UTC)

[edit] Discpreancy between this entry and the entry on Conjoined twins

In this entry, under "Types of twins"/"Identical Twins" it states "Twinning after 12 days post-fertilization will typically result in conjoined twins." with a link to the entry on conjoined twins. However, in the beginning of the conjoined twins entry, it states "Contrary to popular belief, conjoined twins are not the result of an incomplete split of twin embryos; rather, the embryos become joined again after they have already split."

One of these entries is wrong, or this entry is incomplete, and needs a footnote to explain that after 12 days, twinning occurs but with a great possibility of the twins become joined.

The article on conjoined twins is egregiously wrong. I'll find appropriate sources, and update it. Nandesuka 00:52, 18 December 2005 (UTC)

Cool, thats good to know. Thanks!

[edit] Every Other Generation Discrepensy

Is there any proof on the so-called every other generation rule--you know the one that states that not your kids will have twins, but your grandkids will or may?--ChuckDizzle 16:54, 14 January 2006 (UTC)

No~

My mother was a twin, and I'm a twin. Totnesmartin 13:54, 9 December 2006 (UTC)

[edit] oral contraceptives

Removed the line that said dizygotic twins were more likely when conception is soon after the cessation of oral contraceptives

Anyone have a study for this? I know of one that said maybe it was more likely to lead to monozygotic, but it wasn't conclusive and it didn't have findings on dizygotic. - O^O

That section was added by User:Violetriga at 19:36, 12 September 2004. I have asked for a source. -- ALoan (Talk) 23:39, 19 April 2006 (UTC)

It comes from "Mayes' Midwifery - A Textbook for Midwives 12th Edition" ISBN 0-7020-1757-4. violet/riga (t) 18:34, 27 April 2006 (UTC)

[edit] Non-sibling twins?

There was an uncommon case a couple years ago--check it out http://taxa.epi.umn.edu/twinnews/twin_1_2.htm under "A New Type of Twinning" I think that should be included under unusual twinning.

[edit] Predisposition for monozygotic twinning

I have just tagged the following paragraph with {{fact}}:

Fewer than 20 families have been described with an inherited tendency towards monozygotic twinning (people in these families have nearly a 50% chance of delivering monozygotic twins). Some evidence suggests that the environment of the womb causes the zygote to split in most cases

This seems very interesting, and I would be really interested in seeing a reference. For now, none of the documents I have seen mention anything like that, so I noone finds a reference, I'll remove the quote above from the article in the future. Schutz 16:07, 19 April 2006 (UTC)

Good catch. I removed it. Nandesuka 16:43, 19 April 2006 (UTC)

Pity; I am still hoping this is correct and someone will come with a reference... I have not been able to find anything, despite a fair amount of time spent on Pubmed and specialised web sites. Anyone has any idea where to look (or which keyword to use) ? Schutz 22:50, 19 April 2006 (UTC)

That is a really old assertion - added by NuclearWinner (talk • contribs) at 04:58, 30 August 2003 with the comment "improved accuracy, added fun fax re rate of twinning". They made a few edits a few days ago, so it may be worth asking for a source (in fact I see Schutz has already asked). -- ALoan (Talk) 23:34, 19 April 2006 (UTC)

Sorry, I should have mentioned here that I searched for the edit already, so that you don't waste your time searching for it again (especially for an edit that is almost 3 years old...) Schutz 23:42, 19 April 2006 (UTC)

[edit] Recent large additions

The recent large additions to the article were by an anonymous editor and provided no sources. I'm not reverting them though because much of this article is unsourced anyway. The edits appear reputable to me although they are unverifiable without deeper knowledge of the field and links to sources. Please check these edits if you have an expert understanding of biology and can add sources for these additions. — Donama 09:22, 24 May 2006 (UTC)

[edit] The removed section on twins in fiction

==In fiction==

The theme of the confusion among twins or a character simulating being twins is a millenia-old resource of th ecomedy of errors. Plays featuring twins (real or simulated) include the Roman Menaechmi, Shakespeare's The Comedy of Errors, Dumas's The Iron Mask and Bollywood Gol Maal. Sometimes the twins are divided in a good one and the "evil twin". So that the audience differentiates them, each of the twins (often represented by the same actor) has different hairdos, the stereotypical goatee or clothes. Conversely, film child actors are often twins, since labor laws limit the time a child can work. By alternating the twins for the same character, the shooting speed can match that of adult actors.

---

Hello -- I am a twinless twin (my identical brother died at our premature birth). I totally missed any information on fate of surviving twins that necesarrily maintain very often unconscious bond with their deceased half ("lone twin syndrome"). The feelings of being utterly lonely and being only half of some lost whole is common to all surviving multiples. How can I correct this article -- to whom must I write suggestions and provide materials pls.?

Sincerely -- Algis Davidavicius (Shim Gong), shimgong@gmail.com.

[edit] The Olsens

I can't beleave Mary-Kate & Ashley Olsen are not identacal.(misspelled)--Cute 1 4 u 21:06, 17 July 2006 (UTC)

[edit] Polar body twins (identical-fraternal twins)

"Polar body or (identical-fraternal) twinning, is thought to occur when a single egg splits prior to fertilization and a separate sperm fertilizes each half. These twins share 75% of their DNA, and like fraternal twins, can be same gender or boy/girl."

As this section is refuted twice above on this talk page I am surprised to see it still in the article and unsourced. Please add proper sources to confirm this if you return this to the article. Rmhermen 16:27, 12 August 2006 (UTC)

[edit] "Famous Twins" list

This was just completely out of control, so I nuked it. Please remember that Wikipedia is not an indiscriminate collection of information. Nandesuka 03:15, 6 September 2006 (UTC)

Well nuked! There is already such a list at List of twins anyway. Gnusmas 08:19, 6 September 2006 (UTC)

[edit] private language

I noticed we have a stub about Idioglossia, which states that twins sometimes have their own secret language (e.g., Poto and Cabengo or June and Jennifer Gibbons). This would go under human twins, clearly, but right now the focus of the text seems to be entirely on biological aspects, not social ones. I'll try and add something in a little while just so the information's there to build on. Phoenix-forgotten 03:22, 20 September 2006 (UTC)

[edit] discrepancy in describing twinning rates

i've copied conflicting text from two paragraphs in this article. the issue is whether twinning occurs at a rate of 1:150 or 1:250 births. 68.237.196.135 15:20, 29 September 2006 (UTC)

Identical twins Identical twins occur when a single egg is fertilized to form one zygote (monozygotic) which then divides into two separate embryos. This is not considered to be a hereditary trait, but rather an anomaly that occurs in birthing at a rate of about 1:150 births worldwide

Nevertheless, the rate of identical twins remains at about 1 in 250 across the globe

[edit] duration of pregnancy

Where did the 34 to 36 weeks duration of twin pregnancy come from? I'm a mother of twins myself and I have never heard anything different than 37 weeks, and the first link below gives that as well (22 days early is 37 weeks). I've taken the liberty to change it to 37 weeks anyway. 195.96.121.74 21:07, 5 January 2007 (UTC)

[edit] Maury???

Under polar twins it says "There has been one case on Maury where the twins had different fathers but they were fraternal." What on earth does "Maury" mean? Is it a place (an island, maybe), or what? The sentence can probably be deleted as unsourced anecdote, whatever maury is! Gnusmas 20:53, 21 January 2007 (UTC)

It just may be a word that I do not know, but perhaps the "Maury" is referencing the American talk show Maury. That would be my guess.Ultatri 02:04, 13 February 2007 (UTC)

[edit] Ethnicity and twins

Did you know Nigerians have twins for every 22 births? And Inuit the lowest twin rate? Twins and race needs to be added.--HalaTruth(ሀላካሕ) 22:09, 22 January 2007 (UTC)

[edit] Need a better picture

That's a bad picture. It doesn't look like twins, just two kids in a tub. Identical twins would be the best for an image. Wujucokola 09:07, 1 March 2007 (UTC)

[edit] Twins and Society

I don't know about this section... it seems controversial and unsubstantiated. Being a twin myself, I can say that some of these notions are just false.

Polar twins reported: [1]

[edit] Semi-Identical

Im the one who changed the semi-identical section I added a reference but i don't know how to put the in article source, also can someone clean up that part since i did little more than edit what was already there, thx. also how do you post your name at the end? sorry im a Wiki n00b.

BBC news article on the (it claims) first reported semi-identical twins.

What is the difference of reproduction between normal twins and identical twins?