What
Sort of Tests are Available?
1.
Paternity Tests
2. Maternity
Test
3. Twin Test
4. Relationship Test
5. Identity Profiling
6. DNA Banking
Information
on DNA and Identity Tests
1.
DNA and Chromosomes
2. DNA Identity Tests
3.
Accuracy of the Tests
4.
Example 1
5.
Example 2
6.
The At Home Kit How
is a Test Performed?
1. Sample
Registration
2. DNA Extraction
3. DNA Markers
4. DNA Analysis
5. Statistical Analysis
6. The Test Report
Privacy
and Law
1. Privacy
2. Legal requirements
What Sort of Tests are Available?
1. Paternity Tests
The most evident and common application of a paternity test is to
determine whether an alleged father is in fact the biological father
of a child. This information could be helpful for a number of reasons:
-
For
peace of mind when a man wants to confirm that a child
is his own
-
In
custody or visitation disputes when a man wants to confirm
his relationship to the child
-
To
assist a woman seeking child support from a man who denies
he is
the biological father of the child
Two
main types of paternity tests are generally offered:
As
long as the correct procedure is followed for sample collection
there should
be no difference in the accuracy
and validity of the
results obtained by either
of these two.
The main difference between
the two tests lies in the admissibility
of the results as evidence in the Courts of
Law. The requirements for a
Legal paternity test to be
officially recognised in Court
vary between countries, but in general there
must be an independent
third person, usually a lawyer or a court-appointed
expert, who can testify that
each of the samples tested
in the laboratory
really originated from the corresponding donor,
and who can provide evidence
that at no point could the
samples have been switched
or contaminated. The necessary involvement
of a third person and the additional
procedural steps that need
to be employed,
both by the legal representative and by the
laboratory, naturally make
the Legal paternity test more
expensive. It is also usually
necessary for the individuals choosing the
Legal test to travel
to the office or facility of the legal representative
for the test to be performed.
Sample
collection
for
the
Curiosity
paternity
test
can
generally
be carried out at home by the donors themselves.
The
procedure
is easy to understand and can be performed
by
practically
anybody.
In a few words, the choice between a Curiosity
and a Legal paternity test depends on the intention
of using the results as evidence
in a legal dispute. If chances of this are
low, then the Curiosity test offers equally
valid results with more convenience and at
a lower price.
Difference |
Curiosity
Test |
Legal
Test |
Admissible
in Court |
No |
Yes |
At
Home Test Possible |
Yes |
No |
Identification
Necessary |
No |
Yes |
Consent
Necessary |
Consent necessary from all persons tested, and one of
the legal parents if the child is a minor |
Consent necessary from all persons tested, and both legal
parents of the child |
Price
of the Test |
340 € (incl. 50 € for kit) |
640 € (incl. consultation) |
Reliability |
Very high |
Very high |
Turnover time |
3 Weeks |
3 Weeks |
2.
Maternity Test
Maternity tests are similarly employed to determine the relationship
between a woman and a particular child. The test may be useful
in cases of an abducted or abandoned child.
Other applications of paternity and maternity tests
include:
-
Identification of the biological
parents of an adopted child
-
Matching of the respective
biological parents to newborns who may have been accidentally
switched
at birth
-
Confirmation
of parentage of children conceived through alternative
reproduction technologies such as in vitro
fertilization
3.
Twin Test
A Twin Test determines if twins are identical or not. Identical
twins share all of their genes and therefore have identical genetic
profiles. Non-identical twins share a quarter of their
genes on average, just like a brother and sister, and therefore
their genetic profiles do not match perfectly. Genetic profiles
do not change with time, so the tests may be applied to identify
identical twins at any time throughout their lives.
Twin tests might be performed for several reasons:
-
Curiosity
Testing: Parents of twins and twins themselves may wish to
know whether
they are identical or non-identical
-
Medical
Necessity: In medical situations requiring blood transfusions
and organ transplantation, an identical
twin can help save
the second twin’s life. Knowing whether a
twin is identical or not beforehand is thus beneficial
for timely action in
these occurrences
-
Medical Research: Twin studies have provided valuable information
to the research community. Twin studies help to examine
the contribution of environmental and genetic factors
in the
study of ageing,
the study of genetic diseases.
4.
Relationship Test
The
DNA relationship test is similar to the paternity test
but may be applied in a broader sense to test familial
relationships. Applications of this test include:
-
Confirmation
of relationships between reunited family members in case
of adoption
-
Determination
of parentage or grand-parentage for insurance or inheritance
rights claims
-
Proving
kinship to a citizen in order to substantiate claims
for immigration status qualification
5. Identity Profiling
A
DNA identity profile allows the unique identification of
a person. It may also be used as a basis for the identification
of the person’s biological relations. Once a person’s
DNA profile is generated it can be placed in safe storage
for possible future use, often in conjunction with the person’s
will. This can be used whenever the need may arise for possible
future identification or verification of the person or the
person's relatives. Possible uses include the identification
of remains following accidental death and investigation of
inheritance claims by alleged relatives.
We strongly encourage the client to authenticate the DNA Identity Profile through
the use of a third party witness during the sampling phase. Such validation will
ensure that the chain of custody is complete, and will facilitate the use of
the results in a potential Court case or other legal requirements.
GENDIA will send you a report detailing your unique 16 marker profile. It is
recommended that the results are notarized and stored in a secure location or
deposited with your legal advisor.
6. DNA Banking
It
is also possible for a person to store his/her DNA for safekeeping
instead of the DNA identity profile. This DNA can be used whenever
the need may arise for possible future identification or verification
of the person or the person's relatives. Possible uses include
the identification of remains following accidental death and
investigation of inheritance claims by alleged relatives.
We strongly encourage the client to authenticate the DNA through the use of a
third party witness during the sampling phase. Such validation will ensure that
the chain of custody is complete, and will facilitate the use of the results
in a potential Court case or other legal requirements.
GENDIA will send you a sample of your DNA. It is recommended that the DNA is
deposited with your legal advisor, and that this gets notarized.
Information
on
DNA
and
Identity
Tests
1.
DNA
and Chromosomes
Hereditary material called DNA (deoxyribonucleic acid)
is the genetic blueprint of life. It determines the specific
characteristics of each individual. Except for identical twins,
every person's DNA is unique. Consequently, a unique genetic
profile can be created from a person's DNA. This DNA profile
forms the basis of identity tests.
DNA is a long threadlike molecule found in almost all cells
of the human body. An individual's genetic makeup is coded
within the DNA in several functional units called genes. The
entire DNA content of practically all cells is located in 46
chromosomes. These are complex molecular structures consisting
of a long DNA strand.
The 46 chromosomes are grouped into 23 pairs, of which 22
pairs are homologous, meaning that the paired chromosomes are
of the same size and appearance and store information related
to the same inherited traits. The 23rd pair comprises the sex
chromosomes (X or Y) that are important for sex determination
(a man has 1 X and 1 Y chromosome, whereas a woman has 2 X
chromosomes). Each set of 23 chromosomes is inherited from
one biological parent. Thus, every individual has two genetic
complements in their DNA, one complement inherited from the
biological mother and the other from the biological father.
This fact forms the foundation on which DNA paternity testing
is based, since it allows the biological relationship between
a child and an alleged father to be validated or excluded by
a comparison of their DNA.
2.
DNA Identity Tests
In the previous section it was established that by comparing
the DNA of a child and an alleged father, it is possible
to investigate their biological relationship.
In practice, only certain regions in the DNA, called microsatellite
markers or loci, need to be compared to establish biological
paternity. Microsatellite
markers are short fragments of DNA in which the same DNA
sequence is repeated several times. Since an individual has
two genetic complements of DNA, there
are actually two copies of each marker present, one inherited
from each of the biological parents.
Depending on the laboratory, generally between 6 and 16 microsatellite markers
are analysed for determination of paternity. The microsatellite markers used
are standard markers recommended by specialised organisations such as the European
Network of Forensic Science (ENFSI), the Iberoamerican Working Group on DNA
Analysis (GITAD), and Interpol. An important property of these markers is that
the number of DNA sequence repetitions (or frequency) is highly variable within
the general population but strongly conserved from parent to child. As a result,
the frequency of one complement of each of the child's markers matches that
of one complement of the biological mother, whereas the frequency of the other
complement matches that of one complement of the biological father (see
Example 1).
The set of frequencies of the analysed markers constitutes the genetic profile
of a tested individual. A standard paternity test determines the genetic profiles
of the mother, the child and the alleged father. By comparing the three profiles
it is possible to identify the marker in each complementary pair that the child
inherited from the biological mother. By elimination, the remaining half of
the genetic profile was inherited from the biological father. By comparing
this part of the child's genetic profile with the profile of the alleged father,
the Paternity Test determines whether the alleged father is the biological
father or not. A match between the two profiles indicates that the alleged
father is the real biological father (Example 1). On
the other hand, if the profile of the alleged father does not match that of
the child, he is excluded from paternity (Example 2).
3. Accuracy of a Paternity Test
Since it is so specific, DNA paternity testing is a very powerful form of testing.
In a test including samples from the mother, child and alleged father, the
probability of paternity is 99.9% or greater when an alleged father's DNA profile
matches that of the child for all the genetic markers. On the other hand, an
alleged father is 100% excluded from paternity if there is a mismatch between
the profiles of the child and alleged father for three or more genetic markers.
When only a child and alleged father are tested (i.e. a motherless test), the
information provided by the mother's DNA profile is unavailable. Nonetheless,
when there is a perfect match between the DNA profiles of the child and alleged
father, the probability of paternity is generally in excess of 99.9%. A mismatch
in the two DNA profiles for three or more genetic markers implies with 100%
certainty that the alleged father is not the child's biological father.
The accuracy of the test increases with the number of genetic markers included
in the DNA profile. Thus, the result of a test that uses a 16-marker profile
is likely to be more conclusive than one using a 6- or 13-marker profile. It
is therefore important to select a paternity test that uses an adequate number
of markers, especially when only the child and alleged father are tested.
Since family members are more likely to have similar genetic profiles, when
two alleged fathers are related the probability of paternity may be lower than
in standard tests. In such cases it is always best to test both alleged fathers,
since the one who is not the biological father can be excluded with certainty.
If the two alleged fathers are identical twins it is not possible to identify
the biological father, since identical twins have identical DNA profiles.
The reason that it is not possible to determine biological paternity with 100%
certainty is that there is always a very small possibility that the profile
of the alleged father matches that of the child purely by chance. The likelihood
of this happening is generally well below 0.001% (or 1 in 100000) and it depends
to a large extent on the ethnic origin of the individuals involved. The certainty
of biological paternity generally increases with the number of genetic markers
analysed.
4. Example 1
Case 1: The figure shows the result for one
microsatellite marker from a paternity test that includes samples
from the mother (top row), the child (middle row), and the alleged
father (bottom row). In this example, the maternal marker that
has been passed to the child is number 6. This means that the
other marker present for the child (number 7) must have been
inherited from the father. In this case the alleged father matches
the child, since one of his markers is indeed number 7. This
procedure is repeated for all microsatellite markers used in
the test.
5. Example 2
Case 2: The figure shows the result for one
microsatellite marker from a paternity test that includes samples
from the mother (top row), the child (middle row), and the alleged
father (bottom row). In this case the maternal markers are 29
and 30. This implies that the child has inherited 29 from the
mother and the 31.2 complement must have been inherited from
the biological father. Since the alleged father does not possess
this marker it is unlikely that he is the biological father.
In practice this mismatch between the child and alleged father's
DNA must be present in at least three markers to exclude paternity
with certainty.
6.
The At Home Kit
Saliva samples (also called oral
swabs, mouth swabs, or buccal swabs)
For the personal paternity test and the twin test it is possible to use
the special AT HOME KIT from GENDIA. This kit uses saliva as the source of DNA.
The
procedure to obtain a saliva sample is simple and painless, and therefore this
kit is commonly used.
It is recommended NOT
to eat or drink at least one hour before a saliva sample is
taken. Use a separate envelope and swab
for each person. Please complete the information (name, date
of birth, and identification: father/mother/child) on the
envelop before taking the samples.
Take care not to touch the
broad end of the swab, and to use a new sterile oral swab for
each donor. Take the swab out
of the plastic without touching the broad end, and throw away
the plastic.
A sample is taken
by gently rubbing the broad side of the swab 10 times against
both cheeks, under the tongue and behind
the lips, each time for 3 seconds. The swab is then put into
the correct envelop without closing the envelope. Do NOT use
the plastic to put the swab in.
Finally, put the small envelops in a larger
envelop and send this to the GENDIA
laboratory in Antwerp.
Whole
blood samples
The second type of blood sample commonly used
is the whole blood sample. Due to its invasive nature, this method
of sampling requires the service of somebody specially trained and
qualified to draw blood. The sample consists of about 3ml of blood
that is drawn by means of a syringe and deposited in a special container
(called an EDTA tube). The tube contains anti-coagulant and other
chemicals that ensure the DNA contained in the blood is preserved
for the necessary period of time. It is important that the samples
are kept at room temperature.
Tips for successful whole blood sampling
-
It is important to make sure that the sample is correctly labelled
with the name or code number of the donor.
-
For safety purposes and to avoid contamination of the sample,
a new syringe must
be used for each donor.
-
Inform the laboratory
if any of the donors
has recently had
a blood transfusion
or bone marrow
transplant.
-
Samples must be
kept at room
temperature. (Never freeze blood
since this compromises
the quality of
the
DNA!)
How
is a Test Performed?
1. Sample Registration
In case of curiosity testing the samples are usually taken
at home with the at home kit and sent to the GENDIA lab.
In case of legal paternity tests, the samples are usually
taken by a GENDIA physician.
As soon as the samples reach the GENDIA lab they are registered
in the lab's database. Here, data such as the case number
and the date of sample receipt are recorded.
The case number allows the unique identification of a sample
while keeping the donor anonymous to the laboratory personnel.
Once results are obtained, the person in charge matches
the identification numbers back to the sample donors in
order to issue the test report.
2.
DNA Extraction
The saliva or blood samples received by the laboratory contain
the genetic material that is analysed in the paternity test.
The genetic material is called DNA (Deoxyribo Nucleic Acid)
and it is found in the centre (or nucleus) of the cells in
the sample.
Before the DNA can be analysed it must first be extracted and
purified from the other components in the sample.
The first step of the DNA extraction process is to break up
(or lyse) the cells so that the DNA inside is released. This
is achieved by adding a special solution to degrade certain
components of the cell, leaving the DNA floating freely. The
DNA is then dissolved in a liquid and is ready for the next
step of the paternity test.
3.
DNA Markers
Only specific small sections of a person's DNA need to be analysed
in order to perform an identity test. These sections are referred
to as DNA markers. These DNA markers vary between different
persons, and a combination of different DNA markers therefore
constitutes a person’s unique genetic profile. The more
DNA markers are used, the more unique the genetic profile becomes.
Most labs analyse 6 to 16 markers. GENDIA analyses 16 markers.
4. DNA Analysis
Once the DNA markers have been amplified, they are placed
into an instrument called an automatic DNA analyser,
which separates the markers by size. The size information
is measured by means of a laser, fed into a computer,
and analysed with a special software program.
The detection result is displayed in graphic form on
the computer, as show in Example 1 and Example 2. Each
DNA marker appears as two peaks, one from the father,
and one from the mother.
5. Statistical Analysis
Once results from all samples for all the DNA markers have
been collected, they are inputted into a statistical software
program for interpretation. If a given marker does not match
between a child and alleged father, it is likely that the latter
is not the real biological father. For each additional non-matching
there is an increase in the probability that the alleged father
is not the biological father. In fact, if three or more markers
do not match, it is practically impossible that the alleged
father is the real biological father.
On the other hand, a match in the frequencies between an alleged
father and a child for a given marker may occur for two reasons.
It may either be that the alleged father is the real biological
father. However it could also be that the two donors happen
to have identical markers purely by chance. The larger the
number of matching markers between a child and an alleged father,
the higher the likelihood that the latter is the biological
father. If more than 10 markers show a match between child
and alleged father it is practically certain that the latter
is the biological father.
The probability of paternity is defined as a percentage. If
an alleged father is not the biological father, the paternity
test generates a probability of paternity of 0%. If the alleged
father is the biological father, the test usually generates
a probability of paternity on the order of 99.9% or more.
6. The Test Report
The final step in the laboratory procedure for a test
is to issue a report and dispatch it to the person
requesting the
test.
The report includes the following components:
-
A listing of the samples, including
identification information
-
A
description of the method used to perform the test
-
A
presentation and interpretation of the results
-
A
signature of the person responsible for issuing the results
Privacy
and Law
1.
Privacy
All samples are solely used to perform the tests you indicate
on the submission form.
The test report is only sent to the person indicated on the
submission form.
2.
Legal Requirements
For all tests written consent is necessary from all persons
whose DNA is analysed, but not from minors.
There are special regulations for paternity tests:
1. Legal paternity tests
For the legal paternity test it is necessary that all parties
whose sample is tested (child, alleged father and mother) provide
a signed
consent (on the GENDIA submission form).
When the test involves a minor (< 18 years), additional
consent from the legal father and mother (or legal guardian)
is necessary (Art. 7 of the Belgian privacy Law). If there
is written consent from the legal father from a minor but not
from the legal mother , you can order a personal (curiosity)
test.
2. Personal (curiosity) paternity test
For the Personal (curiosity) paternity test it is necessary
that all parties whose sample is tested (child, alleged father
and
eventually
mother) provide a signed consent (on the GENDIA submission form).
When the test involves a minor (< 18 years), additional consent
from at least one of the legal parents (or legal guardian)
is necessary (Art. 7 of the Belgian privacy Law).
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