twin: Definition, Synonyms from Answers.com
These "half-identical twins" are hypothesized to occur when an unfertilized
..... "Monozygotic twins discordant for sex". ...
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WikiAnswers - Since it is possible to have identical twins of ...
Cells and Genetics question: Since it is possible to have identical twins of
different genders could there be a nondisjunction in the sex chromosome?
wiki.answers.com/Q/ Since_it_is_possible_to_have_identical_twins_of_different_genders_could_there_...

What is the difference between fraternal and identical twins ...
Identical twins have the same genetic makeup because they are formed from the
same pair of gametes. They look alike and are the same sex. ...
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WikiAnswers - Can a boy and a girl take birth as identical twin
Science question: Can a boy and a girl take birth as identical twin? my question
is : monozygotic twins always have the same sex or they may be of different ...
wiki.answers.com/Q/ Can_a_boy_and_a_girl_take_birth_as_identical_twin

What are identical twins?: Information from Answers.com
The babies will be identical twins, which means they will have the same genes,
be of the same sex, and look amazingly alike. ...
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WikiAnswers - Can identical twins be different genders
Can identical twins be a different sex? Can siamese twins be different genders?
Do identical twins be different genders? What genders can make an identical ...
wiki.answers.com/Q/ Can_identical_twins_be_different_genders

identical twins: Definition from Answers.com
identical twins Monozygotic twins who share 100 percent of their genetic ... of
the same sex, identical genetic makeup, and closely similar appearance. ...
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WikiAnswers - Are identical twins developed from one egg or two
This is the traditional way that so-called identical twins are produced.
Identical twins are always the same sex. (I use the term 'so-called,' because
they ...
wiki.answers.com/Q/ Are_identical_twins_developed_from_one_egg_or_two

multiple birth: Information from Answers.com
In the one-egg, or identical, type of twinning, a single fertilized ovum divides
to form two complete organisms. Such twins are always of the same sex, ...
www.answers.com/topic/multiple-birth

WikiAnswers - Can boy and girl be identical twins
During development slight changes may occur but the sex always stays the same.
... So basically, identical twins start off as one cell that divides and ...
wiki.answers.com/Q/Can_boy_and_girl_be_identical_twins