When we are out, I always get asked if the girls are twins and that's almost always followed by whether or not they are identical. The following information comes from here.
■Monozygotic (MZ) multiples (can be twins or higher-order multiples) were created when one fertilized egg split to form two or more embryos.
■Dizygotic (DZ) or trizygotic (TZ) multiples were created when two or more eggs were fertilized.
■Triplets and higher-order multiples can be any combinations of monozygotic and di/trizygotic.
Monozygotic multiples are commonly known as “identical” and di/tri/quadzygotic are known as “fraternal.” Some people assume that because 2 kids are "identical" that they are the same in every way. This is not true. When an egg splits, the two new eggs go down their own genetic path. The DNA can change in very simple ways. Besides that, there are internal and external conditions that make the two new individuals exactly that, Individuals.
Did you know:
■that monozygotic twins have more variation in birth weight than dizygotic twins, but by age 10 monozygotic twins are closer in weight and height than dizygotic twins?
■there are more sets of female monozygotic twins than male sets, and more sets of female conjoined twins than male sets?
■for most cancers, the risk of getting cancer isn’t any higher even if your twin has it
■even though monozygotic multiples aren’t supposed to run in families, there are some cases where it seems to recur in families or to occur more often than expected in families with dizygotic multiples
■language delays and learning disabilities seem to be more common among multiples
■dizygotic twins may run in families and may be passed down by both men and women (with men they can pass the trait to overovulate to their daughters)
■there are mirror image twins where some traits are opposites (one is left-handed and one is right-handed, one has hair that parts on the left and one on the right, etc)
We have never had the girls tested but the pathology report from their birth proves that they are identical.
There is also a third rare form of twining! Many the term used by our Genetic's team is semi-identical, there are two theory's to this type of twining one is the egg is double fertilized and then splits, my team believe's that with my twins genetic breakdown my egg split prior to conecption which means my girls have identical maternal DNA but there paternal DNA is that of siblings they have more in common genetically than fraternal but less then full identical's.
ReplyDeleteThey have only found this rare form of twining when doing testing like we did since my twins looked identical at birth but since differ. They did 3 DNA test's to confirm what the first test showed.
So when people ask if they are identical or not I confuse them!
There's another type too, which occurs when a fertilized egg splits, but one of them loses some of the DNA. It's possible, in theory, to have a set of male/female identical twins. The missing DNA would cause Turner Syndrome in this case. I honestly don't know if that has been proven to have occurred or just speculated. I'm sure there are all sorts of other things that occur with twin DNA that science is just starting to uncover.
ReplyDeleteI love genetics stuff. I'll have to look into what you mention above for Thing1 and Thing2.
Yup Valerie that is another type!
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