In This Article
In This Article
A DNA test can prove that two people are related and the degree to which they are related. To prove that two people are twins, they’d need to undergo a twin zygosity DNA test.
DNA stands for deoxyribonucleic acid. It carries genetic information, which is something each person shares with their ancestors.
DNA shows a link between more distant relatives, including:
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It depends on whether they are fraternal twins or identical twins.
Identical twins or monozygotic twins are two different people who grew from a single fertilized egg and one sperm.
Once the sperm reaches the egg, the fertilized egg splits into two identical cells, which eventually manifest in the same physical characteristics and nearly genetically identical people. As monozygotic twins grow, they are an exact match of one another and share the same DNA.1
This means that their genetic signature is almost if not an exact match. This is commonly observed in many DNA tests that cannot tell identical twins apart.2
Take note, however, that recent studies have also shown that the 99.9% figure can also fluctuate slightly (around an average of 5.2 mutations can distinguish them), given some possible genetic mutations the eggs go through.6
Fraternal twins, or dizygotic twins, are two separate eggs fertilized by two separate sperm. They are not identical, and aside from being in utero and born at the same time, they are biologically no closer than any other siblings.5
If twins are identical twins, DNA will show this. Identical twins' DNA profiles are identical. They look the same, they are the same sex, and they have the same DNA.
If they are fraternal or non-identical twins, their DNA sample will show only that they are siblings. Fraternal twins' DNA profiles are very similar—approximately 50%, although this figure fluctuates—but no more similar than siblings born separately.5
Not only can a twin DNA test help you determine your twin relationship, but it can also help an expectant mother determine if her twins are fraternal or identical while she is pregnant.
Sometimes, a woman releases two eggs instead of one, and both are fertilized. This means that different combinations of DNA occur when the cells start to multiply, leading to non-identical twins.
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Yes, you can get a DNA test to see if you're identical twins.
You can use a DNA profile or a twin zygosity test to determine if you're identical or fraternal twins.3 This will require comparing the DNA profile of each twin to the other and seeing if they're an exact match or not. Identical twins often share over 99.9% of their DNA since they grew from the same combination of chromosomes, and the egg split later on to make two copies.4
These tests are relatively accessible and will only take anywhere between five to seven business days (depending on the company; some may take additional business days or even fewer).
If you or anyone you know wants to undergo twin zygosity testing (whether it's for health reasons or just out of curiosity), here's how it works for most companies (some may vary):
Your results will reveal if you're identical twins or fraternal twins.
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Yes, you can. Several companies offer at-home twin tests and other relationship tests.
They'll send you a sample collection kit as well as their own instructions for sending it back, wait time, etc.
However, you need to keep in mind that at-home DNA testing is not considered a “legal test.”
It’s legal to take the test, and it can provide you with information. However, the results are not recognized by the court system. A legal test must be performed by a doctor and/or at a DNA testing clinic for the legal system to officially recognize.
If you’re interested in taking a DNA test for legal reasons, speak to an attorney or contact the court to determine what constitutes a legal test in your situation.
It depends on the company, but many companies and facilities start pricing at a baseline of $100.
Yes, but it is extremely rare. And in most cases, nobody will ever know that there are two different fathers.
If two different sperm fertilize two different eggs at approximately the same time, it can result in two babies that appear to be fraternal twins.
DNA testing would show them to be only half-siblings.
Twins are detectable very early in a pregnancy, even in the first trimester.
In the case of fraternal twins, there will always be two fertilized eggs, so it will be easy to detect them. When it comes to identical twins, they can't be detected until the egg splits, but this happens very early in the development process, so it shouldn't be too much of a surprise.
Twins can be classified as:
Di-di, mo-di, and mo-mo classifications are not always an indication as to whether twins are identical or fraternal.
Di-di twins, which are twins with their own separate inner and outer sacs and placentas, are detectable at week five of the pregnancy. Heartbeats might not be discoverable yet, but the sacs have formed and are visible.
It's a rare occurrence, but two placentas sometimes fuse into one, which makes it seem as if fraternal twins are identical. A DNA test would prove otherwise.
All fraternal and a third of all identical twins are di-di.
Mo-di twins aren’t detectable until after six weeks. These twins share a chorionic sac but different amniotic sacs. There is only one placenta in this type of pregnancy.
Mo-di twins share one placenta and one outer membrane, but each has its own inner membrane. This is the most common type of identical twins.
Mo-di twins are always identical.
Mo-mo twins also aren’t detectable until after six weeks. These twins share both chorionic and amniotic sacs.
Mo-mo twins share a single placenta and outer and inner membranes. This is a very rare occurrence and accounts for only about one percent of all identical twins.
Mo-mo twins are always identical.
If it is impossible to tell for sure during the pregnancy that twins are identical, DNA testing is performed after birth.
This can be done using a blood sample from the placenta(s) or by swabbing the cheek cells from each baby.
Samples can be taken from the comfort of your own home and sent to a lab for analysis.
There can be a number of reasons, some of them being curiosity, health reasons, and even looking into possibilities of organ transplant or blood transfusion, among other potential medical emergencies.
Twins can look much alike without being identical, the same as siblings born at different times. Confirming that twins are indeed identical can clear up any simple curiosity or even inform health decisions.
Another reason is so that twins can take part in scientific studies. Twin studies are still being explored, so their voluntary help could further the research. The test shows that the twins originally split from one egg, so identical twins are able to provide information based on their genetics.
Twin studies are very common, but participants must prove they are identical or fraternal before they are admitted into most studies.
It's important to know if you're pregnant with twins because they can come with more complications, like:
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