Identical Boy Girl Twins?

by Laurel
(Winnipeg, Canada)

I have identical boy twins and was told the other day that identical boy twins are pretty rare but that the rarest type of identical twins are identical boy girl twins. Wasn't sure what to say to that one....

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Oct 25, 2013
Yes, it is possible
by: Anonymous

Remember that "identical" in this case has nothing to do with physical attributes such as a penis or vagina. Rather, it is determined through the DNA of this type of monozygotic twins. Yes, it is possible that a boy and girl be monozygotic twins by virtue of the above referenced posts regarding the extra or "dropped" y chromosome. The female twin is likely to have Turner's Syndrome which is a chromosomal condition that alters development in females. One major consequence is that this condition usually makes it impossible for the female twin to conceive a child because of an absence of ovarian function.

Oct 06, 2011
Rare but possible
by: Anonymous

Actually, there can be identical boy/girl twins if the sex gene of the embryo has an extra x chromosome (the fertilized egg would be an xxy) then when the egg splits one can have xx (girl) genes and one can have xy (boy) genes. Rare but possible.

Oct 06, 2010
Only 4 ever recorded cases
by: Anonymous

Boy/girl identicals are possible but so rare that there are only 4 ever recorded cases. It generally happens when after the cell splits, the girl (I think) loses the chromosone... Basically doesn't ever happen, but since it has...

Aug 18, 2010
by: Anonymous

I watched a video made by National Geographic called "Multiples in the Womb". You should watch it. B/G identicals are very rare but possible. The mother doesn't have the normal XX gene, she has an extra Y. So, she's XXY. The egg gets fertilized by a sperm carrying the X gene. When the egg splits, one half get the XX combo - a girl, and the other half somehow gets that extra Y gene to get XY - a boy. I know I probably sound crazy, and I don't know all the technical mumbo jumbo. I know I probably didn't explain it right. Look up "Multiples in the Womb" by National Geographic. It explains it on there.

Jul 05, 2010
by: Anonymous

where is the identical part of one having a vagina and one having a penis??

Jul 04, 2010
by: Anonymous

Actually, I just read on not an hour ago that idetical male and female twinsDo exist, but it didn't go into much detail.

Jun 17, 2010
by: stacey

Id say monoamniotic/monochorionic twins are the rarest identicals-no dividing membrane xx as mentioned before-you cant possibly have identical boy/girl doh!!

May 09, 2010
My tech said..
by: Anne

Most of those cases where they were identical boy/girl one was a hermaphrodite. So, something was really wrong..She looked into it, being an ultrasound tech and all..

May 05, 2010

A set of boy/girl twins can only be fraternal (dizygotic). Boy/girl twins can not be identical (monozygotic).

However, there have been a few reported cases of a genetic mutation in monozygotic male twins. For some reason, after the zygote splits, one twin loses a Y chromosome and develops as a female. The female twin would be afflicted with Turner Syndrome, characterized by short stature and lack of ovarian development. It's extremely rare; less than ten cases have been confirmed. Given the odds, it's safe to assume that 99.9% of all boy/girl twins are fraternal.

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