Yes. Conjoined twins are always identical (monozygotic) twins, and identical twins are always the same sex.There is a theoretical case where identical twins could be opposite genders, when the babies are female but in one of the females, a branch of one X chromosome breaks away; however, I don't believe this has ever been observed.
Identical twins are formed from a single fertilized egg that splits into two embryos. Because they share the same genetic material, identical twins are always the same sex. Opposite-sex twins are typically fraternal twins, formed from two separate eggs fertilized by two different sperm.
No. All identical twins are the same sex. Judith and Hamnet were opposite sexes, and so were fraternal twins.
They can be. While identical twins always have to be the same gender, fraternal twins usually are not. However this is not always the case. Identical twins occur because they inhabit the same egg. Fraternal twins because two eggs were fertilized at the same time. So fraternal twins could be the same gender, but usually they are of the opposite gender.
Yes.
No, monozygotic twins would be the same sex. Monozygotic twins come from one single fertilized egg, or zygote, which then splits to create two separate zygotes which will be genetically identical, or "identical twins", which will always be of the same gender.
fraternal twins have two different chromosomes
The DNA of identical twins and of clones is, apart from random, environmentally produced mutations, 100% identical. The only difference is that clones are produced on purpose through advanced bioengineering techniques while identical twins happen as an accident of nature. Identical twins are, in a sense, natural clones.
Twins are identical because they come from the same egg.
No. In order for them to be identical they needed to start off as the same cell and divide so at first their DNA is identical meaning they have the same sex. 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. The term for boy-girl twins is furturnal. You can however have boy-boy twins and girl-girl twins that are not identical and they are also called furternal. So basically, identical twins start off as one cell that divides and furternal are two individual cells. There is polar body twinning, that's when the egg splits before fertilization, and that can cause a male and a female. This is called semi identical twins or half twins. They share 75% of their genetic markers.
do identical or non identical twins share the same placenta
Identical twins form when an egg is released from the ovary and is fertilised by a sperm and then splits into two. They then form naturally. Non-identical twins form when two eggs are released from the ovary and then fertilised by a sperm. They also form naturally. Identical twins have to be of the same sex (two boys or two girls) because they have come from the same egg which contains the same DNA. Non-identical twins can be either boy and girl or of the same sex (two boys or two girls) because they came from two different eggs and so have two different sets of DNA.