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Fraternal twins make up the majority of twins and account for 90% of multiple pregnancies. Unlike identical twins, this kind of twinning results in babies that have different sex and look different. Read this in-depth information about how they are formed, how they differ from identical twins and answers to your other questions.
Fraternal twins are dizygotic. They developed from two sets of sperm and egg that produces two babies that can be both girls, boys, or a combination. Unlike identical twins, fraternal twins are more independent. They do not share the same placenta and develop a separate amniotic sac.
In a normal reproduction process, the sperm travels to meet the egg after sexual intercourse or in-vitro fertilization. If two eggs were released, two sperm will be able to fertilize the eggs that will eventually produce two genetically unique babies.
Twinning happens in several ways and produces higher order multiples depending on the number of eggs produced and the zygosity. This usually happens during hyperovulation, when a woman releases multiple eggs – mostly two.
In the case of fraternal twins, two zygotes are produced with a genetic background like that of any two siblings born at different times. The only difference is that twins are conceived at the same time.
No, they do not have the same DNA makeup as identical twins do. Just like any siblings, fraternal twins share about 50% of their DNA and half each of their parent’s DNA. Each twin gets half of the mom’s egg and the half from dad’s sperm.
Since fraternal twins do not share the same DNA, they also do not share the same chromosomes at the time of fertilization. However, they still share parts of their parents’ DNA so they may look alike, but not exactly identical.
Even twins that look alike can be distinguishable. Twins who were raised in the same home and were educated the same way, develop individual tastes and personalities.
Yes, they can be both boys or both girls. Unlike identical twins who share the same sex chromosomes from a single fertilized zygote, fraternal twins were produced by two separate zygotes that carry different sex chromosomes from their father.
Monozygotic twins or identical twins, however, are always the same gender. Doctors and health professionals usually identify if same-sex twins are identical or fraternal through other factors such as having shared placenta, chorion, and amniotic sac or through DNA testing. DNA testing is the surefire way to determine if twins are identical or fraternal.
Since conception happened for each egg, each egg carries the sex chromosome of the father. A girl has XX chromosomes while a boy has XY chromosomes. A boy-girl combination is the most common form of fraternal twins.
The chances of having fraternal twins are very much like with any kind of multiples. There are certain factors that increase the odds of a woman to conceive more than one baby at the same time.
Yes, they can be. The factors above influence a woman’s odds of conceiving twins or multiples. Hyperovulation can be genetic, but it can result in multiple pregnancies of two, three, four, and higher multiples. It just so happen that twins account for 90% of multiple pregnancies and having fraternal twins is more common than identical twins.
Like identical twins, fraternal twins start to bond in the womb. They learn how to share nutrients and start to reach out to each other as they grow and develop. However, unlike identical twins that share the same amniotic sac, chorion, and placenta, fraternal twins grow in separate amniotic sacs and have separate placentas. They cannot physically reach out to each other as identical twins do, but they can feel each other in the womb and give each other some nudge.
These are all the facts about how fraternal twins are formed and other information regarding their genetic makeup and development. Fraternal twins are remarkably amazing.
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