can identical twins be opposite sex?

Question

m any my friend are in an argument, and i know that identical twins cant be opposite sex because its fertilized by one sperm, and sperm are either xx, or xy. she claims its two different sperm in one egg, which wouldnt happen. whos right?

Answer 1

In over 99.9% of cases identical twins will be the same sex - they are what it says on the tin, identical. 1 egg, 1 sperm, 2 babies.



However, there is a very rare anomolie that occurs where you can get twins that have come from the same egg and sperm but are opposite sexes. There have been three recorded cases of this.



http://www.bellaonline.com/articles/art1291.asp



Quote;



'Although extremely rare, there are now documented cases of boy/girl identical twins.



... the phenomena could realistically take place ... with an egg being fertilized by one sperm, then dividing itself into two separate eggs, which is also the exact way identical same-gendered twins begin life.



However, in the case of boy/girl identical twins, those fertilized eggs initially both contain male DNA only.



We all learned in high school biology that male DNA have an X-chromosome and a Y-chromosome and it’s the Y-chromosome which makes him male and female DNA have two X-chromosomes. Well, in the case of mixed-gendered identical twins, which always begin male, the Y-chromosome disappears, and science has offered no explanation for it.



As a result of losing the Y-chromosome, the male twin becomes female with an XO DNA chromosome pairing. '



It is explained even better here:



http://www.bio-medicine.org/biology-definition/Twin/#Mixed_sex_identical_twins



Mixed sex identical twins



In extremely rare cases, identical twins have been born with opposite sexes (one male, one female). In these cases, identical twin boys are conceived, but, during the twinning process, one twin loses a Y chromosome (boys have chromosome type XY while girls have XX). Without a Y chromosome to trigger the production of male sex hormones , this fetus develops as a girl by default, but a girl with only one X chromosome (chromosome type XO). The co-twin is unaffected, and develops as a boy as normal.



As a result of her genetic abnormality, the girl will suffer from Turner syndrome, which is distinguishable by short stature, folds of skin at the neck, abnormal development of secondary sexual characteristics, and an intellectual deficit known as space-form blindness . Turner syndrome can occur in any birth (including singletons, fraternal female twins, or identical female twins), so an individual with Turner syndrome is not automatically a twin. Turner syndrome occurs in about 1 in 10,000 of all births, but cases of mixed sex identical twins are much rarer—only three cases have been documented.



All this aside, your friend is WRONG as 2 egg in one sperm would cause a miscarriage or Molar Pregnancy, not opposite sex twins. Identical twins have to have the same egg and sperm.



(There is one recorded exception where twins occured due to two sperm in one egg but they were only semi-identical)



http://news.softpedia.com/news/Shocking-Semi-Identical-Twins-One-is-Hermaphrodite-50415.shtml



.

Answer 2

1

Answer 3

One newer explanation of this phenomena, in addition to the one explained above, is that a single fertilized egg contains three rather than the customary two chromozomes through rare abnormality. This trio could consist of two X's and one Y chromosome. After the fertilized egg splits, one of the three chromosomes in each egg will unravel and disappear having no use in the egg's developing nucleus. In this particular case of different sex monozygotes, one egg will lose the Y and become female while the other will lose one of it's X chromosomes and become a male. These different sex monozygotes develop mostly normally and are the closest genetically that opposite sex twins can be containing about half of the identical original genetic material of their parents. However they will still be less homogenous than same sex monozygotes and aren't truly fraternal, but also not truly "identical".

Answer 4

Mixed Chromosome Twins

Answer 5

From what i know your friend is wrong, id bet money on it cuz im not wrong very often lol jk wit ya, ok there are fraternal twins and identical twins fraternal is two eggs in the female that are fertilized by two sperm cuz i don't see how its possible for one sperm two fertilize two eggs. Then there are identical twins scientifically known as mono-zygotic twins which is the result of one egg fertilized by one sperm that splits into two fetuses resulting in identical genetic makeup, in all but a few RARE chromosomal defect cases they are the opposite gender which has nothing to do with two different sperm in one egg in fact i think its impossible for two sperm to enter one egg cuz once the egg is breached it releases a chemical that makes the egg impenetrable by another sperm if my memory serves me right. (so in short basically all identical twins are the same gender boy/boy girl/girl or xx xy as you so aptly put it) ...any questions???

Answer 6

identical twins sex

Answer 7

RE:

can identical twins be opposite sex?

m any my friend are in an argument, and i know that identical twins cant be opposite sex because its fertilized by one sperm, and sperm are either xx, or xy. she claims its two different sperm in one egg, which wouldnt happen. whos right?

Answer 8

With zygotic twins were there are one male and one female, the female might only have one X chromosome often referred to as Turner Syndrome. But technically they would be identical twins but in reality, they will not look the same.

Answer 9

I guess the answer could be yes in one of those rare case scenarios but generally no. Like a previous poster said, even if they are labeled identical, if one has a penis and the other has a vagina, those two things are not identical now are they?



To another previous poster that said all fraternals are boy/girl....that is incorrect. Fraternal could be b/g, b/b, or g/g.

Answer 10

Identical twins are one sperm and one egg that splits. They have identical DNA and cannot be the opposite sex. It's not possible for two sperm to fertilize the same egg... it just can't happen.



Fraternal twins are two eggs and two sperm. They can be the same sex and look similar, or they can be a blonde, blue eyed boy and a brunette brown eyed girl... heck, they can technically have different fathers!

Answer 11

Identical Twins cannot be the opposite sex. That would make them fraternal because their genes would be different, obviously as one is XX and the other XY.



I found a website that may help answer your questions. On it, it states that twins occur in the following situations:



* Two eggs may be released at the same time and fertilised by separate sperm. These will result in non-identical or fraternal twins and can be of opposite sexes. They will look no more alike than any other siblings.



* One egg may become fertilised and will split into two within the next 2 weeks. These twins will be of the same sex and they will be genetically identical.



* Siamese twins are identical twins but the split occurs later, between 13 and 17 days.

Answer 12

Identical twins cannot be of the opposite sex. this is because, identical twins were from a single sperm and egg. Identical twins happened when there is 'default' in cell division during mitosis. so you're right.

Answer 13

Identical twins contain identical DNA. They are produced as a result of an egg (which has been fertilised by a single sperm) splitting in two. Therefore if they contain the same DNA they cannot be opposite sex. Now you can say "I told you so" :)

Answer 14

It's very rare, but YES, identical twins CAN be the opposite sex. Look it up.

Answer 15

well you are both got half right



egg cells can only be fertilized by one sperm

and its impossible to have 2 sperms fertilize 1 eggs because there would be 2 many chromozomes



most identical twins are same sex but 3-5 cases have been confirmed or opposite sex identicals

Answer 16

you are definitely correct. it is commenly thought that a boy and girl can be opposite sex, but it isn't true. I am a triplet and my brother and I aren't identical; we can't be.



maddie

Answer 17

NO. Identical twins are always same gender because they form from a single zygote that contains either male or female sex chromosomes. 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 Syndrome, characterized by short stature and lack of ovarian development.

Answer 18

You are right, they can't be opposite sex. One fertilized egg splits, into 2 babies that are genetically identical. Fraternal twins can be opposite sex but are not always.

Answer 19

They cannot be different sexes as they are IDENTICAL.



Identical twins occur when one egg is fertilized by one sperm and then the cell splits and creates two fetuses.



Non-identical twins (I forget what they're called) are created when two eggs are fertilized by two differetn sperm. They can be different sexes.

Answer 20

Only fraternal twins can be opposite sex. identical twins are called identical for a reason. If one was a boy and one was a girl they couldn't be labeled as identical now can they. Wow they aren't drinking are they?

Answer 21

sperm are either x or y all of the eggs are x. xx=female xy=male. no it is not possible. one sperm fertilizes one egg then the egg splits into two and grow(put very simply) and you have identical twins.. regular twins are just when two separate sperm fertilize two separate eggs(i.e. fraternal twins). therefore it is entirely possible that they will be different sex. but they are not identical. so if only one sperm fertilizes one egg it will either be xy or xx and when the egg splits to create identical twins they will be the same xx or xy depending on which chromosome entered the egg first. two sperm cannot fertilize the same egg. only one gets in. hope this settles your argument. lol.



EDIT: for everyone who says " yes in very rare occasions" no. they are not actually identical.

Answer 22

actually sperm are always xy, eggs are xx. you take one from the egg and one from the sperm. the egg always contributes an x,because that is all they have the sperm can contribute either x or y, which determines the gender of the fetus. . That being said, you are right, identical twins have to be the same gender, otherwise they are not genetically identical. they can still look an awful lot a like though.

Answer 23

you are right! identical twins share the same DNA, so therefore it would be impossible for identical twins to be boy/girl



fraternal twins is a different story

Answer 24

If they are not identical, they are not maternal. Meaning, if they have different parts, they are fraternal: NOT IDENTICAL. It makes perfect sense. Identical means identical. Maternal twins are basically clones of themselves because the egg divides into two. When twins are paternal, it means two eggs were dropped and both were fertilized. Maternal meaning coming from the female and paternal meaning coming from the male

Answer 25

You are correct. Even if some things are the same (hair color, eye color, skin tone, etc.) with a boy/girl twin combination, if they are not the same gender, they are not identical.

Answer 26

you are right! identical twins are called identical for a reason if a boy and a girl were identical that would be quite awkward

Answer 27

Nope they can't. Identical twins are when the egg divides sometime after ONE sperm has fertilized it. YOU WIN!! :P

Answer 28

Yes, Identical twins can be the opposite sex

Answer 29

Yes, in identical twins, the fertilized egg splits.

But the babies are still the same gender.

Fraternal is always opposite pairs because they are 2 different eggs.

Answer 30

well i was researching it myself and saw this site hopes it gives you the information that you are looking for

Answer 31

no they can't be

Answer 32

No.

Identical twins can not be opposite sex.

Answer 33

NOO!!!!



I am an identical twin.

Answer 34

your right

Answer 35

Technically yes but you and I both know you can't be Identical if one has a penis and the other, well you know....

Answer 36

yes,can be.

Answer 37

sure ive seen it before

Answer 38

its incredibly rare but it can happen