Proving genetic relationships requires a DNA or parental test and there are a number of different tests available. In this article, Dr Nigel Chatwin provides some background on DNA testing and discusses the options available to patients.
What is parental testing?
Parental testing, or more commonly called paternity testing, is based on comparing the DNA profile of a child with the profile of the presumed parent (usually the father). The child carries both the genetic profile of the mother and the father. The laboratory will search for similar patterns of the child’s genes with either parent. The test can conclude with almost one hundred percent certainty if a person is the genetic parent.
When is DNA profiling used?
In most cases, this test is used to prove the genetic relationship of the alleged father, and is therefore commonly called a paternity test. DNA profiling is also used in genealogy DNA, forensic science and genetic research.
When was it developed?
The DNA profiling technique, or genetic fingerprinting, was first reported in 1984 by Sir Alec Jeffreys at the University of Leicester in England and was published in the journal, Nature . He was later awarded the Nobel price for his research. At the same time, a new process to amplify segments of DNA almost indefinitely, called Polymerase Chain Reaction or PCR, was developed by Francis Mullis (1993 Nobel Prize Laureate) with Cetus Corporation .
How does it work?
DNA profiling mimics the biological process of DNA replication, but confines it to specific DNA sequences of interest. This process revolutionised the genetic research, forensics science and parental profiling .
The genetic profiling starts with taking a DNA sample, from either as a swab from the mouth, blood or other fluids or tissues from the individual. The DNA sample or ‘loci’ is then amplified by PCR. The amplified genetic segments are separated and identified by a process called electrophoresis.
In parental screening, specific DNA segments or loci are compared with the presumed parent loci. If they match, the test confirms the genetic link between the child and presumed parent.
The types of tests available 
Chain of custody parental DNA testing
This process helps ensure that the results will be legally defensible in court, should the individuals ever need their results for legal purposes (such as obtaining child support).
The chain of custody process satisfies legal requirements by proving the following:
The DNA samples were collected by a neutral third party - someone who has no personal interest in the outcome of the test. This neutral third party is normally a doctor or nurse.
The tested parties were positively identified at the time of sample collection. To be positively identified, a tested individual must present a government-issued photo ID and be thumb printed.
The collected DNA samples were made tamper-resistant. The samples are tamper-taped at the collection site and are posted to our laboratory in secure packaging. Upon arrival at the laboratory, the samples are carefully inspected for any evidence of tampering.
When attending a DNA sample collection appointment, the patient will be required:
To present government-issued photo identification
To present identification (such as a birth certificate) for any tested minors for whom the have parental responsibility
To complete a Client Identification and Consent Form. If the patient has parental responsibility for a tested minor, they will be asked to complete a consent form for the child as well
To be thumb printed and/or photographed.
Peace of mind paternity testing
Peace of mind parental testing is used to satisfy personal curiosity about the paternity of a child. The results from this test are not legally defensible, and therefore cannot be used for legal purposes.
Non-invasive prenatal genetic testing
Non-invasive prenatal genetic testing incorporates DNA technology by preserving and analysing the foetus DNA that is found within the mother's bloodstream. The test is highly accurate and results are available within eight working days. The test is simple, only requiring a blood sample from the mother and presumed father.
This early test is available from the ninth week of pregnancy onwards. This test requires modern and sophisticated genetic technology, which only a very specialised centres can provide.
Other genetic tests
Ancestry test - find out about your DNA genealogy going back thousands of years
Siblingship testing from DNA - helps two individuals verify whether they are full or half siblings
Twin zygosity DNA testing - determines whether twin siblings are identical twins or fraternal twins
Y-chromosome DNA - determines whether two or more males are biologically related through their father's side of the family
Mitochondrial DNA - a type of DNA that is found in the mitochondria of every human living cell which produces the energy for each cell. Mitochondrial DNA is passed from a mother to her children, making it useful for tracing individuals’ maternal lineage. Both male and female direct descent inherit mtDNA from their mother, but only females can pass their mtDNA to their children.
-  Jeffreys A.J., Wilson V., Thein S.W. (1984). "Hypervariable 'minisatellite' regions in human DNA". Nature 314: 67–73
-  The effects of business practices, licensing, and intellectual property on development and dissemination of the polymerase chain reaction: case study
- Joe Fore 1, Ilse R Wiechers 1 2 and Robert Cook-Deegan 1
- Journal of Biomedical Discovery and Collaboration 2006, 1:7 doi:10.1186/1747-5333-1-7
-  DNA Profiling, Wikipedia
-  DNA Diagnostic Centre UK