fraternal twins can have separate fathers.
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.
Homozygous means "the same egg." That refers to identical twins. Identical twins are always the same gender since they have the same chromosomes.
Identical twins can share the same placenta during pregnancy, but it is not always the case. In some instances, identical twins may have separate placentas.
fraternal twins have two different chromosomes
Yes, they are twins. Being born on the same day to the same parents makes them twins, even if they are identical.
fraternal twins have two different chromosomes
no, sometimes one is taller
No, identical twins can be in the same or separate sacs. Identical twins form when a single fertilized egg splits into two embryos. Whether they share the same sac or have separate sacs is determined by when the split occurs during development.
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.
fraternal twins have two different chromosomes
Identical twins will have the same father, so a paternity test is done just like for any kid. With fraternal twins, it is possible, but very, very rare, to have different fathers for the babies.
Twins are identical because they come from the same egg.