Twin - Information from Answers.com
Monozygotic twins are genetically nearly identical and they are always the same
sex unless there has been a mutation during development. The children of ...
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Biology and sexual orientation - Information from Answers.com
They studied 289 pairs of identical twins (monozygotic or from ... for same-sex
attraction of only 7.7% for male identical twins and ...
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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 are ...
wiki.answers.com/Q/ Are_identical_twins_developed_from_one_egg_or_two

Can boy and girl be identical twins
During development slight changes may occur but the sex always stays the same
. Boy-girl twins are always two different cells meaning that they are not identical ...
wiki.answers.com/Q/Can_boy_and_girl_be_identical_twins

Why can't identical twins be of the opposite sex
Identical twins have to be the same sex because they both come from one egg.
This means that they have identical genetic material, and therefore identical ...
wiki.answers.com/Q/ Why_can't_identical_twins_be_of_the_opposite_sex

What are twins that dont look alike caled
Answer: Improve. Fraternal. They develop from separate ova and are not
genetically identical, so look different, can have different sex etc. Unlike "identical
twins.
wiki.answers.com/Q/ What_are_twins_that_dont_look_alike_caled

multiple pregnancy: Definition from Answers.com
They may be the same or different sex, occur twice as frequently as identical
twins, and have a mortality rate of 11.5 percent. Identical twins represent the ...
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How do twins develop
They may or may not have the same blood type, and may or may not be of the
same sex. Approximately 2/3 of twin pregnancies are fraternal twins. "Identical ...
wiki.answers.com/Q/How_do_twins_develop

Can you be pregnant with twins that were conceived at different times
For identical twins then the answer is no as the egg splits after being fertilized by
a single sperm. Thus the result is same sex identical twins. Fraternal twins ...
wiki.answers.com/Q/ Can_you_be_pregnant_with_twins_that_were_conceived_at_different_times