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More than just fraternal and identical?

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More than just fraternal and identical?

Post by moonbeam on Fri Jul 05, 2013 6:17 am

I had no idea that there were more types of twins beyond just the two common ones!  

Most people are familiar with Identical and Fraternal twins, but in reality, there are 7 different kinds of twins. They are: identical, fraternal, half-identical, mirror image twins, mixed chromosome twins, superfecundation, and superfetation. However, the reason most people are only familiar with identical and fraternal is because the other types are quite rare.

Half-identical twins happen in rare occasions when twins inherit the same genes from the mother, but different genes from the father. Mirror image twins are identical twins that develop mirror-image features (for example, one is right-handed and the other left-handed). Superfecundation is when the mother ovulates more than one egg in one cycle and has more than one partner during her fertile period. Superfetation is the development of a second fetus when one is already present in the uterus.


Source: http://www.omg-facts.com/Sex/There-Are-More-Than-2-Types-Of-Twins/42337

The article above doesn't say what "mixed chromosome" twins are (even though they mention it), so I did a bit more searching and found that

Mixed chromosome twins, also known as chimerism, is believed to occur if two separate sperm fertilize two separate eggs that fuse, producing individuals with different sets of chromosomes. Some have been identified that have more than one distinct red blood cell type and individuals who are both XX and XY (the sex chromosomes – XX being female and XY being male.) This phenomenon may be associated with fused placentas causing circulation intermixing. This is a very rare condition, which is more common in other mammals.

Source:  http://twinmother.com/different-types-of-twins/


A third article says there are TEN types of twins.  http://wiki.answers.com/Q/How_many_different_types_of_twins_are_there

I find this to be really fascinating..I'm probably the only one, though!
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Re: More than just fraternal and identical?

Post by boatlady on Fri Jul 05, 2013 8:59 am

Twins are interesting on all sorts of levels.
Like you, I was not aware of all the different types, and thanks for posting the links with the information.
I remember when training looking at material about identical twins separated at birth, whose life experiences throw such a lot of light on the nature/nurture debate and the development of personality.
I've also spoken to parents of twins who swear their babies develop communication between themselves at a very early age and appear to be able to coordinate their challenging behaviours so as to keep parents in a state of near panic for most of their waking hours. I've also met parents who swear their twins seem deliberately to alternate nap times so one is always awake and active, and mum (or dad) gets no rest.
In literature and myth, the notions of the doppelganger and the 'evil twin' provide much material for speculation on the nature of individuality and the personality.
My word, there's the material for several PhD's in there for anyone who wants to write them.
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Re: More than just fraternal and identical?

Post by oftenwrong on Fri Jul 05, 2013 11:34 am

Every recent scientific advance in the field of genetics points towards designer babies, particularly when infertility is the motivator, where the latest advance is to involve 3 humans in the production of an embryo. The only moderator is whether the general public will decide that eugenics is not a dirty word.
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Re: More than just fraternal and identical?

Post by moonbeam on Fri Jul 05, 2013 3:04 pm

My younger brothers are fraternal twins, actually. As far as my recollection goes, they didn't ever do any of the private language stuff, nor were their habits and personalities opposite. They were always close, of course, and still are.

Eugenics is a slippery slope. There is obviously some good to be had - if it could eradicate cancer and other major debilitating diseases and birth defects. I wouldn't want it to go to the level of having a "perfect" society though.

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Re: More than just fraternal and identical?

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