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X Chromosome Test - Sisters

The X chromosome is one of the two sex determining chromosomes. Its peculiarity is that it is present in all people, but only women have a double X chromosome, each from one of the parents.

The  X chromosome DNA test consists of analysing the markers of this DNA, in order to define with great precision whether women share a paternal relationship. It thus allows a search for paternity without the DNA of the presumed father. 

What is a Chromosome X test?

X chromosome DNA Test

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You can do a DNA test to find out the parentage at home in a private setting. The order can be made directly on the internet from your home in order to receive the sampling equipment at home.

It often happens that the participants can be geographically distant, in this case the laboratories offer to send a genetic kit to each of the participants. 

Nevertheless, it is still impossible to get  a DNA test in a pharmacy , moreover only a laboratory with genetic analysis equipment and accredited by international standards can provide the result for a DNA test.  

How to do an X chromosome test?

Sibling DNA testing can be done 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 was used for the test?

X Chromosome Test Participants

X chromosome test - relation link

In a paternal line, each child inherits from his father, a perfectly identical and relatively unchanged over the generations, sex chromosome .


In this context, all women from the same biological father share this gene in common.

In girls who have a double X chromosome, one of the X chromosomes comes from the mother and the other X chromosome is inherited from the father who himself inherited it from his own mother.


As this chromosome remains practically unchanged from generation to generation, genetic analysis makes it possible to verify whether two sisters come from the same biological father, even in the absence of their presumed father. 

By deduction, when a father transmits the  X chromosome to his daughter, he himself inherited it from his biological mother. Thus it is possible to define a paternity with the DNA of the biological grandmother of the presumed father.

Who can take part in this parentage test?

- An X chromosome test can be performed between the paternal grandmother and her granddaughter

X chromosome Test - grandmother
X chromosome test - grandchild


- Two or more sisters can participate in the  test

- Sisters may or may not share the same biological mother (half-sister)

- The biological mother must participate under certain conditions 

X chromosome test - sisters
x chromosome test - halfsisters

1. The two sisters have the same biological mother:


When the sisters share the same mother, it is essential that the mother also participates in the parentage test to obtain reliable and accurate results. Because this will allow the laboratory to isolate the maternal genes and thus focus on the X chromosomes that comes from the father. 

If you are in doubt about parenthood between siblings or when it is not possible to provide a maternal sample, it is best to do a sibling test .

2. The two sisters do not have the same biological mother (half-sister):

When sisters do not share the same mother, it is not necessary to provide DNA from the biological mother, only recommended. The results will still remain very reliable, because the X chromosome from the father will be more easily detectable and compared between the half-sisters.

3. X chromosome test between grandmother and granddaughter:

A granddaughter and her paternal grandmother can take an X chromosome test to verify parentage to that paternal family line. The grandmother will have transmitted an X chromosome to her son, who will in turn have transmitted it to his daughter. This comparison gives a reliable and precise answer on the paternity of the granddaughter, even in the absence of her biological father. 

The conditions concerning the analysis of the X chromosome: 

No, it is not possible to do this test with cousins or other family members. The transmission of the X chromosome occurs randomly between children from the same biological mother. Thus it is possible that the X chromosome of a brother is not the same as his sister. It is then the same for transmission to uncles, aunts or cousins of the family. 

Can we do an X chromosome test with cousins?

Consent is the agreement you give to the laboratory to use your DNA for the purpose of carrying out a genetic analysis. It is mandatory if you wish to take a sibling test. Consent can only be given explicitly by an adult and fully lucid person. This agreement must be drafted after having received information about the outcomes of the test, through 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?

X Chromosome Results

- 5 to 7 days using buccal swabs for all participants

- 10 days minimum if one of the participants uses non-standard samples


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 test between sisters? 

The results are presented in the form of a table:

- Each  column  corresponding to a participant

- Each line has a gene

- The composition of the gene is represented by one or two digits per participant 

How to read the results of the genetic analysis?

The reliability and authenticity of the X chromosome test depends on several factors:

- The quality of the samples

- Laboratory accreditation

- The choice of the test according to the family situation

How reliable are the results?

The quality of the DNA will depend on the collection and 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 an X chromosome 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. Depending on your situation, you have the possibility to ask the laboratory for an extended comparison of the number of loci. The extended comparison improves the precision and therefore the reliability of the results. 

Genetic Laboratory

The choice of laboratory is a very important step when you want to do an X-chromosome DNA test. You should choose the lab based 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?

Maternal line research

The mitochondrial DNA test allows anyone to compare this specific DNA from the biological mother in order to determine a common maternal line. 

Paternal line research

The analysis of the Y chromosome makes it possible to define whether the grandfather and the grandson come from the same paternal line. By deduction if they are biologically related.

How can I do a DNA test?


DNA testing is done by comparing the genetic profiles of two or more people. Alone, it is not possible to define a relationship or find out who his father is, for example. You must do the test with family members, if you do not have any, you must first find potential people likely to be.


Follow our guide to discover the possibilities of   research, paternity   or   maternity research .


How can I do a DNA test with a deceased person?


The complexity of the situation poses a serious technical and administrative problem. As a general rule, the consent of the person concerned must be obtained beforehand and explicitly, without this no identification by genetic fingerprints can be carried out after death, but certain countries authorize it.  The second problem is the collection of samples from a deceased person, which remains a delicate operation. Exhumation is still possible under legal procedures, but the samples may not provide enough genetic information. It is therefore possible to use non-standard samples for a private test.


What type of sample can I use?


Laboratories always recommend using saliva as the primary sample. It is the easiest to provide and contains enough genetic information to perform all tests. But if your situation does not allow you to use it, you can use other types of so-called non-standard samples such as hair, nails, blood...


Non-standard samples always represent an additional cost to your order and have a degree of success which can vary according to several factors (conservation, date and method of sampling, type of sample, etc.) We offer a list and advice on the use of  non-standard samples .


Does the reliability of my test depend on my samples?


No, the reliability does not depend on the type of sample you use or the collection method. If you have results, your samples provided enough genetic information for the test.

On the other hand, if your samples are not viable for the test or do not contain enough genetic information, the laboratory will warn you and ask you to send back other samples in order to continue the analysis. In this case, the laboratory invoices the new analysis, it is in this sense that it is important to choose the starting sample carefully.


Can we test from different addresses?


Yes, labs always offer an option to send you multiple kits if participants are unable to test together. This can also be done even if the participants are in different countries.


Can we come to the lab for a test?


Generally no, the companies that offer you online tests are commercial companies that work in partnership with the laboratories to relocate all the logistics of the procedures and the customer service. This allows the laboratory to concentrate solely on the work of analysis and thus it is very rare that they provide a place open to the public. In addition, the requested sample collection does not require the intervention of a professional.


How can I be sure that the samples belong to the person concerned?


If you do a non-legal test and you doubt the origin of the samples, you will never be able to know from the DNA profile alone whether the person who put their name on the form is the same person who provided the samples.

In this case, you must organise yourself beforehand and put a doctor in your confidence so that he can guarantee the authenticity of the samples and can verify the identity of the participants.

Under no circumstances should the participant be in contact with the samples. The kit must be sent to the doctor who must return it to the laboratory.


Can a DNA test be reimbursed by social security?


No, DNA tests are not considered a medical act and reimbursed by social security, but some complementary health insurances offer it.

Therefore, pay attention to the offers of free DNA tests on the internet offering to go through the reimbursement of social security.


Can the consumption of medication or drugs have an impact on a DNA test?


No, no substance can alter a person's DNA. But the samples you send to the lab can be contaminated or degraded by many environmental factors. Take care to keep them in paper envelopes, avoid handling them with your fingers, and above all do not use a plastic bag.

Frequently Asked Questions

Relationship DNA testing compares the genetic profiles of two or more people to determine a common biological heritage. In general, the test highlights the similarities and differences that make up your genetic fingerprint and evaluates your match rate in order to give you results corresponding to your search for a relationship.

Under no circumstances can this study be established without comparing different individuals , because your DNA is unique and does not contain the genetic profiles of your family, but only its heritage.

Do you want to remove any doubt about your biological origin or that of a loved one? But  you don't   know which test is best suited to your situation? Follow our guide !! On  we provide you with guidance on the tests currently available by putting you in the position of a search for paternity or maternity . Go for it ! It's simple and free and it will allow you to already have solid information before contacting the laboratory.

Which DNA test to choose?

The DNA Relationship Test

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