The twin DNA test is a genetic comparison to establish whether twins have an identical DNA profile or not.
This analysis is able to determine whether twin sisters or twin brothers are identical or fraternal twins.
Furthermore, the twinning test does not make it possible to define whether people are twins or simple brothers and sisters.
It is important to do this test knowing that the people are from the same multiple pregnancy.
The test can be done after birth with buccal samples only.
What is a Twin test?
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It is possible to do a DNA test for twins at home in a private setting. The order can be placed directly on the internet from your home in order to receive the sampling equipment at home.
Today, it is still impossible to obtain a DNA test in a pharmacy, only a laboratory with genetic analysis equipment and accredited by international standards can provide the result for a DNA test.
How to do a DNA test with twins?
The DNA test for twins can be carried out with:
- Saliva samples (sterile buccal swabs)
- Non-standard samples : Like hair, nails, toothbrush...
Be careful, you must follow the instructions and respect the conditions so that the samples provide enough genetic information for your test.
What type of sample is used for the test?
The Participants of the Twin test
Twins are brothers and sisters resulting from a multiple pregnancy, but it would be a mistake to assume that all twins are alike.
Doing a twin test between twins can confirm whether they share identical genetic profiles or not. Confirmation of this comparison can then establish whether they are identical twins or fraternal twins.
Identical twins are the result of a single fertilisation of an egg by a sperm.
The embryo, thus formed by this fertilization, then divides in two to generate two fetuses which entirely share the same genes.
So they are always of the same sex : two girls or two boys.
This is also called Identical or Monozygotic Twins.
The fraternal twins are the result of a separate double fertilization occurring around the same time.
Thus two separate eggs are fertilized by two different sperm and the fertilized eggs then develop separately in the same uterus.
In this construct, the twins are dizygotic, “fraternal twins ” so they are similar to all other siblings, meaning they only share half of their DNA.
Fraternal twins can be of the same or opposite sex and most often with dissimilar physical characteristics.
The twin test can be done with the DNA of two or more twins resulting from a multiple pregnancy. The DNA of the parents is not recommended nor taken into account since the comparison is done directly between the genetic profiles of twins.
It is not necessary to carry out a twin test between brothers and sisters since by deduction they are not from the same pregnancy, so they do not have identical genetic profiles.
Consent is the agreement you give to the laboratory to use your DNA for the purpose of doing genetic analysis. It is mandatory if you want to do a DNA test.
Consent can only be given explicitly by an adult and fully lucid person. This agreement must be written after having received information about the results of the test, by a contract or a consent form.
It is against the law to do a DNA test without the person's consent.
For minors, consent must be provided by one of the legal parents.
What is consent for a DNA test?
DNA Test Results
- 4 at 7 days using buccal swabs
This delay is calculated from the moment your samples arrive at the laboratory. Transport time is not taken into account.
What are the analysis times for a Twin test?
The authenticity and reliability of the twin DNA test depends on several factors:
- The quality of the samples
- Laboratory accreditation
How reliable are the results?
The quality of the DNA will depend on the samples taken and the storage of the samples. It is therefore important to follow the instructions of the laboratory in order to ensure that you receive results.
Accredited laboratories meet the requirements relating to the analysis process, management of resources and equipment, impartiality and confidentiality of information. For a Twinning test, the laboratory must have ISO 17025 accreditation.
The reliability of the result depends on the number of genes compared.
All the laboratories offer tests on an average of 15 to 22 genes (Loci STR) to make the comparison between the participants.
The twin test offers a 100% reliable negative result and a 99.9% reliable positive result.
The results are presented in the form of a table:
- Each column corresponding to a participant
- Each line has a gene from the profile
- The composition of the gene is represented by one or two numbers per person
Participants must have a similar full genetic profile to be considered identical twins.
If the match is perfect on all rows, the relationship is concluded, otherwise it is rejected.
How to read the results of a DNA test with Twins?
The choice of laboratory is a very important step when you want to do a twin test. You should know that each of the laboratories has specific services, so please choose the one that suits you depending on your situation.
You must choose a laboratory according to:
- Your family situation and available participants
- The confidence that the laboratory inspires through customer feedback
- The transparency of the company concerning its activity and your expectations
How to choose a reliable Laboratory?
Why do a DNA test between twins?
There are many reasons why twins or parents of twins want to do a DNA test for twins.
Curiosity : beyond physical traits and a similar character, the twinning test can be wanted for private and recreational purposes of curiosity to determine if siblings have a profile identical genetics.
Medical Necessity : It is important to know if the twins have and share genetic and hereditary diseases. In order to better protect yourself if symptoms appear.
It is also interesting to be able to know their compatibility if medical operations are to be expected, such as during a blood transfusion or a transplant. An identical twin is the ideal candidate to guarantee the success of a surgical intervention, because the risk of rejection of the transplanted organ is ruled out since they share the same antigens.
A medical error : whether during childbirth or by IVF, doing a twin test can thus confirm whether the two brothers or sisters are indeed from the same fertilization and therefore rule out the slightest medical error in the laboratory or at the maternity ward .
Doubt of paternity : the twin test does not make it possible to define the paternity of twins. On the other hand, if the twins are fraternal twins, it remains possible, but rare, that the paternity of the twins is double. In this case, it is much more reliable to do a paternity DNA test between the father and the children: Paternity Test .
Can we do the Twin test remotely?
Yes, you can take saliva samples remotely, before sending them back to the laboratory. In this case, each participant will receive their DNA kit to take the samples at home. Everything must be returned within 3 months of your order, as DNA on mouth swabs only have a shelf life of 3 months. The analysis begins when the laboratory receives all the samples.
How to do a Twin test in Pharmacy?
It is currently impossible to order a DNA test in pharmacies. Genetic analysis is offered by accredited laboratories that offer their services online or on site.
Can we do a Twin test between brothers and sisters?
It is technically possible for the laboratory to compare the DNA of siblings to determine whether the genetic profile is similar or not. But if you already know that the participants are not from the same multiple pregnancy, then the test will not help you. Because the twin test does not make it possible to determine a relationship.
If you are looking for a paternal bond between brothers and/or between sisters: Sibling Test
Frequently Asked Questions
You can do a DNA test even if the participants are geographically distant; even in different countries.
Several possibilities are realized depending on the availability of participants and the DNA test you want to do.
Remote DNA Test
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