"Identical" twins

Question

What is the proper Spanish to be used to describe identical twins when one is female and one is male? gemelos identicos is for identical boys, gemelas identicas is for identical girls

Answer 1

Actually opposite sex identical twins are possible

1. Boy/Girl Identical (Monozygotic) Twins Identical (monozygotic) twins are always same gender because they form from a single zygote that contains either male (XY) or female (XX) sex chromosome. However, there have been a few reported cases of a genetic mutation in male twins where one twin loses an Y chromosome and develops as a female. The female twin would be afflicted with Turner's Syndrome, characterized by short stature and lack of ovarian development. Of course, another explanation for gender differences in identical twins is an identical twin who undergoes a sex change operation.

http://multiples.about.com/od/funfacts/tp/uniquetwins.htm

Answer 2

I'm no geneticist, but my understanding is that male and female twins can only be fraternal, because they come from two different eggs fertilized by two different sperm. That's how their genetic material is different, resulting in one boy and one girl. Identical twins happen when the egg splits; by that time the sex has already been determined by the single sperm that fertilized the original egg.

Answer 3

Aside from the incorrectness of the statement, in Spanish when there is a mix of males and females you default to male: gemelos identicos.

Answer 4

If one is female and the other is male they are definatley not identical twins.