Identical boy/girl twins?

[CLHCO]

I refreshed my rusty twin knowledge after that last thread. I found an article that suggests identical boy/girl twins exist? And here my mother-in-law and I used to joke about the number of people who would ask if my twin brother and sister-in-law are identical.

 

http://8e.devbio.com/article.php?id=111

 

Obviously, they would be the rare exception to the rule though.

 

The whole process is fascinating.

[Tracey in TX]

Too tired to read the mentioned article. I have heard of bg id twins, but it is incredibly rare if it exists at all. That is disputed by many a physician. It certainly does defy all logic. I'm utterly fascinated by reproduction and its remarkable outcome.

Our id girls are mirror-twins. I know they are, but it's too bizarre sometimes to be believable--even by their mom :)

[CLHCO]

Too tired to read the mentioned article. I have heard of bg id twins, but it is incredibly rare if it exists at all. That is disputed by many a physician. It certainly does defy all logic. I'm utterly fascinated by reproduction and its remarkable outcome.

Our id girls are mirror-twins. I know they are, but it's too bizarre sometimes to be believable--even by their mom :)

 

Yes, I met a pair of mirror image before. Even the swirl of the back of their head was opposite. In my twin rabbit trail tonight I did learn that opposite handedness is not necessarily a sign of mirror image but things like that are. My girls are identical - not mirror image - but they are opposite in their ear dominance. The genes can do wacky things even with identicals. It gives me a whole new view of the cloning controversy. In reality, you don't really "clone" a human. Even a genetic match will be very different in the long run.

[RoughCollie]

I don't understand how b/g twins can ever be identical when their bodies are obviously different.

[CalicoKat]

Yes, I met a pair of mirror image before. Even the swirl of the back of their head was opposite. In my twin rabbit trail tonight I did learn that opposite handedness is not necessarily a sign of mirror image but things like that are. My girls are identical - not mirror image - but they are opposite in their ear dominance. The genes can do wacky things even with identicals. It gives me a whole new view of the cloning controversy. In reality, you don't really "clone" a human. Even a genetic match will be very different in the long run.

 

They do have the left/right hand thingy. Their birth marks are identical but on the opposite side of their bodies. Their personalities are opposite - outgoing and introvert. They wear their hair the same except their parts on opposite. And they hate each other, but they're also very loyal.

 

They've also got this weird twin thingy going on that even though they live distant they still do things the same. I can guarantee that if one twin calls me I'll be getting a call from the other twin shortly--even though they haven't spoken with each other! My dh thought I was making this up but after 15 yrs of marriage even he starts looking at the clock after one calls because it's usually within an hour.

 

It was weird growing up with them because ironically I was often mistaken as their "triplet" because I look so much like them too.

[Snickerdoodle]

:)

[CLHCO]

Here is an article I found on mirror image. It offers some interesting things on what it isn't but still acknowledges that, though they certainly exist, there isn't a good theory to why or how.

 

http://www.twinstuff.com/mirrors.htm

 

Like I said, my girls are not mirror image. They get along wonderfully, both are right handed, same head swirl, same baby strawberry marks when infants, etc. But they do have an opposite on ear dominance and leg dominance when you see how they lead in a gallop or ride scooters. I tend to think that comes from a trained behavior when young from them each lining up on a different side of me to hold hands, talk, be read to, etc. It was just the ear closest to me.

 

I agree that it doesn't make sense that boy/girl identicals exist. I guess it comes from an initial chromosomal abnormality that then manifests itself differently upon development? I admit I'm taking the article's word for it.

[Storm Bay]

I've NEVER heard of this, but I have heard of partially identical twins. This is a relatively new discovery with modern DNA work, so perhaps these idential bg twins are only partially identical. In these situations, only part of the DNA strand is identical, and it's caused controversy over the theory that no more than one sperm ever produces a viable life. I'd love to be able to cite the article, but it was in a science magazine read while putting in time at the library. As Dave Barry would say, I'm not making this up! (only I'm really not. And I haven't read Dave Barry in years.)

[Mrs. Readsalot]

I remember learning that identicals come from an egg that splits and that egg can only be either male or female. Makes sense to me.

[Amy in Orlando]

I've never heard of this - cool.

 

Cracks me up too. My twins are 14 and my mil still insists that they are "nocturnal."

[CLHCO]

I remember learning that identicals come from an egg that splits and that egg can only be either male or female. Makes sense to me.

I agree that this is what is normally the situation but I guess there are chromosome abnormalities or other issues with DNA transferring in from another egg that can cause some wacky things. I read recently that people with 2 different colored eyes are in this category as well. They essentially have some other DNA that was absorbed into them early on.

 

The more we learn the more we realize how little we know.

[Janet in WA]

Yes, I've read about that too. I agree -- fascinating.

[Pam "SFSOM" in TN]

Cracks me up too. My twins are 14 and my mil still insists that they are "nocturnal."

 

So THAT's why they cried at night when they were newborns! :D

[Barb_]

I don't understand how b/g twins can ever be identical when their bodies are obviously different.

 

Okay, the way I understand it from the article is this:

 

When an egg (X) is fertilized by a Y-chromosome sperm, you get a boy (XY). Likewise, an egg (X) fertilized by an X-chromosome sperm gives you a girl (XX). An XY zygote that splits would ordinarily give you male identical twins, but if by chance the split is confused, you can wind up with one child who is XYY (a boy with an extra Y-chromosome in his genetic makeup) and a girl who only has one X chromosome, inheriting only her mother's genetic material and not her father's (X0). So they are identical in the sense that they started out monozygotic, rather than from two eggs and two sperms, but they only inherited the identical genetic material from the mother...not the father. In fact, genetically she doesn't even have a father. Weird, huh?

 

Barb

[CLHCO]

Okay, the way I understand it from the article is this:

 

When an egg (X) is fertilized by a Y-chromosome sperm, you get a boy (XY). Likewise, an egg (X) fertilized by an X-chromosome sperm gives you a girl (XX). An XY zygote that splits would ordinarily give you male identical twins, but if by chance the split is confused, you can wind up with one child who is XYY (a boy with an extra Y-chromosome in his genetic makeup) and a girl who only has one X chromosome, inheriting only her mother's genetic material and not her father's (X0). So they are identical in the sense that they started out monozygotic, rather than from two eggs and two sperms, but they only inherited the identical genetic material from the mother...not the father. In fact, genetically she doesn't even have a father. Weird, huh?

 

Barb

Yes, that makes sense. She would basically be a clone of her monther then? The boy would be an XYY, which I remember reading puts him at high risk for higher aggression and other issues.

 

Hurts my head.

[Barb_]

Yes, that makes sense. She would basically be a clone of her monther then? The boy would be an XYY, which I remember reading puts him at high risk for higher aggression and other issues.

 

Hurts my head.

 

Hmm, not really a clone of her mother because every X-chromosome carries a different set of traits. Otherwise all girl children in the family would be clones of mom. But yeah, that's pretty much it. The article also mentions that the boy child could simply be XY and the extra Y-chromosome somehow vanishes. Since I'm not clear on how that would happen, I conveniently left it out :cool:

 

Barb

[Amy in Orlando]

So THAT's why they cried at night when they were newborns! :D

 

:eek:ROFL - yep. And that's why one has that "dark" hair and the other is fair. Honestly, she simply does not get it AT ALL. My poor twin boys have been trying to explain it to her for the past six years - they make charts, draw pictures, talk slowly ... All no go. They remain "nocturnal."

[Lolly]

I have a bit of trouble getting pg and staying that way, so we have very closely monitored pregnancies. The fertility specialist was only able to locate one corpus luteum which would mean that one egg was released. We expected to have identical twins. Of course, he could have missed a second corpus luteum, but he doesn't think so and seems quite sure that only one egg was released. We were quite surprised when our girls were born and had different blood types. The doc thinks that only one egg released, split, and both were fertilized by different sperm. It is extremely well documented to happen in other animals. It is just being explored as being possible in humans. My girls are nothing alike. (Some people would dispute this. Few people could tell them apart before they turned 9. How you can't tell the difference in a brunette and a blond (dark), I don't know.) If the doc is right, Dh's contribution was very different for each one!

[Tracey in TX]

My ID girls were tested at 2y/o. They are 99.997% likelihood identical. Clearly are mirror twins. left/right handed, opposite cowlicks, and--my favorite--lose teeth on opposite side of mouth. Giggles loses her tooth and several days later Darling Dash follows on opposite side. It's too doggone adorable!

[Storm Bay]

Hmm, not really a clone of her mother because every X-chromosome carries a different set of traits. Otherwise all girl children in the family would be clones of mom. But yeah, that's pretty much it. The article also mentions that the boy child could simply be XY and the extra Y-chromosome somehow vanishes. Since I'm not clear on how that would happen, I conveniently left it out :cool:

 

Barb

 

Well, most girls have an x from their dad, plus not all of a girl's characteristics are carried on that x chromosone. However, it's not really that simple because during meiosis (the process of double division that leads to ova and sperm) some genetic recombination occurs, which is why you can inherit traits from both side of your mother's family at once. ie the 50 percent of genes inherited from one parent can come from both sides of that parent.

 

However, new genetic decoding information is revealing some fascinating things. Also, the theory about how sometimes the egg doesn't always divide all the way and that's why you get conjoined twins is being re-examined. Many now believe that the eggs fully divide, but then touch at a critical stage and reattach. Where they reattach determines how the twins are connected (by the head, from the chest, etc).

[Brigitte]

I haven't read the article, but a PBS special on multiples a while back said that there is a theory that left handed singletons were mirror twins, but the right handed twin did not "make it" very early in the pregnancy and was reabsorbed. Interesting to me, since I am a lefty and so is my oldest sister.

[Janet in WA]

 

Many now believe that the eggs fully divide, but then touch at a critical stage and reattach. Where they reattach determines how the twins are connected (by the head, from the chest, etc).

Or a parasitic twin situation.

[3littlekeets]

Okay, I must admit, I'm a little green with envy. I would love to have identical twins. I have two lefty boys and one righty girl. Maybe I should try again:D.

 

But, all I know is that Mary Kate and Ashley are "nocturnal" twins, not identical. That was a shock to me, LOL. :eek:

[Storm Bay]

I haven't read the article, but a PBS special on multiples a while back said that there is a theory that left handed singletons were mirror twins, but the right handed twin did not "make it" very early in the pregnancy and was reabsorbed. Interesting to me, since I am a lefty and so is my oldest sister.

 

Interesting, as I have one dc who is a lefty. However, how about those of us with mixed dominance, or like my grandfather who was considered completely ambidextrous (I know some say that's impossible now)? Just a thought. Of course, there's no way to be sure.