The most common DNA testing used in practical genetics

1. DNA testiNg
NohA L. ibrAhim

2. Prenatal Paternity Test
• Chorionic Villus Sampling (CVS)
The CVS procedure is performed during the 10th
and 13th week of pregnancy. This procedure
involves the removal of a small amount of
placental tissue for testing.
• Amniocentitis
The Amniocentitis procedure is performed during
the 14th and 24th week of pregnancy. Guided
by ultrasound, the OB-GYN will use a long
needle to collect Amnio fluid samples through
the abdomen.

3. Prenatal Paternity Test
• Prenatal DNA paternity testing produces
conclusive results with 0% probability of
paternity if the alleged father is not biologically
related to the child or with greater than 99.9%
probability of paternity if the alleged father is the
biological father of the tested child.

4. Paternity DNA Test
• DNA paternity testing determines the biological
father-child relationship between a man and a
child. Every individual’s DNA or genetic
fingerprint is unique except for identical twins.
• The DNA paternity test compares the DNA
fingerprints between the tested man and child to
determine if the child inherits half of his/her DNA
from the alleged father.
• Mother’s participation is optional although her
participation helps to exclude half of the child’s
DNA fingerprint inherited from her, making the
data analysis easier.

5. Maternity DNA Test
• DNA maternity testing determines the biological
mother-child relationship.
• Applications for Maternity DNA Test
1. Immigration DNA Test
2. Adoption
3. Surrogacy

6. Grandparentage DNA Test
• Grandparetnage DNA testing determines if an
individual (or a couple) and a child are
biologically related as grandparent(s) and
grandchild. It is often used to determine paternity
indirectly in cases where the alleged father is
deceased or unavailable for testing.
• Since we all inherit half of our DNA from our
biological father and half from our biological
mother, we inherit a quarter of our DNA from
each of our biological grandparents.

7. Siblingship DNA Test
• In the siblingship DNA test, two individuals are
tested to determine whether they share one or
both of their biological parents.
• Full siblings share both of their biological parents
and half siblings share one of their biological
parents.

8. Other DNA Tests
• Y-STR DNA Test
This DNA test determines if two males are paternally
related. The Y-Chromosome is passed from father to son
relatively unchanged through many generations. Males
sharing the same male ancestor have the same or very
similar Y-STR DNA profile.
• mt DNA Test
This DNA test determines if two individuals are maternally
related. The mtDNA is passed from mother to children
relatively unchanged through many generations.
Individuals sharing the same female ancestor have the
same or very similar mtDNA sequences.

9. Other DNA Tests
• Twin Zygosity DNA Test
The twin zygosity DNA test is used to determine if twins are
identical or fraternal. Every person’s DNA is unique
except for identical twins. If the twins share the exact
same DNA profiles, they are identical. If they don’t share
the exact same DNA profiles, they are fraternal.
This DNA test is used for personal curiosity or to help solve
health problems when a twin needs an organ or tissue
donor. The identical twin is a perfect choice as a donor in
these medical circumstances.

10. Other DNA Tests
• Avuncular DNA Test
The avuncular (aunt/uncle) DNA test is used to
determine relatedness between a child and
his/her uncle/aunt when the biological parent
that links the relationship is deceased or
unavailable for testing. Participation of the child’s
other parent is strongly encouraged for more
conclusive results.

11. Genetic Reconstruction DNA Test
• A genetic (family) reconstruction DNA test determines
biological family ties between a child and her paternal or
maternal relatives when the alleged parent is deceased
or unavailable for testing. It is typically used as an
indirect way to determine paternity or maternity.
• In the genetic reconstruction DNA test, the child’s DNA
profile is compared with the DNA profiles of at least two
of the alleged parent’s close relatives. Since everyone
inherits half of the genetic materials (DNA) from the
biological father and half from the biological mother,
close relatives share a significant portion of their DNA
profiles.

12. Forensic DNA Test
• The forensic DNA testing technology has been
applied to identify suspects and victims in violent
crimes, and discover identities of victims of
natural or plotted disasters.
• By analyzing and comparing reference samples
and biological materials such as blood, tissues,
and finger nails left behind at a crime scene,
forensic DNA scientists are able to link suspects
and victims to a specific crime.

13. DNA Typing and Banking
• DNA typing and banking services provide individuals with
their DNA profile and preserve their DNA specimen for
future genetic testing when needed. Each individual’s
DNA profile (or genetic fingerprint) is a permanent
means of identification.
• Universal Genetics provides DNA banking service to
store DNA in a medically secure facility that maintains
the viability of DNA for future testing. The preserved
DNA can be used for genetic disease diagnosis,
ancestral lineage or paternity testing to solve legal issues
such as inheritance claims when the tested party is no
longer available for testing.

14. DNA Test Results Interpretation
• It is routinely test 16 genetic markers that are
known for being highly differential between
individuals. A DNA paternity test compares the
sizes of these markers between an alleged
father and a child.
• Each DNA marker contains two alleles, one
inherited from the biological mother and the
other from the biological father. The DNA test
finds out whether there is at least one match out
of the two alleles on the same marker from the
alleged parent’s and child’s DNA.

15. DNA Test Results Interpretation
DNA Marker Mother Child Alleged Father
D21S11 28, 30 28, 31 29, 31
D7S820 9, 10 10, 11 11, 12
TH01 14, 15 14, 16 15, 16
D13S317 7, 8 7, 9 8, 9
D19S433 14, 16.2 14, 15 15, 17

16. DNA Test Results Interpretation
• The partial results indicate that the child and the alleged
father’s DNA match among these five markers.
• Each marker is assigned with a Paternity Index (PI),
which is a statistical measure of how powerfully a match
at a particular marker indicates paternity.
• The PI of each marker is multiplied with each other to
generate the Combined Paternity Index (CPI), which
indicates the overall probability of an individual being the
biological father of the tested child relative to any
random man from the entire population of the same
race.
• The CPI is then converted into a Probability of Paternity
showing the degree of relatedness between the alleged