DNA paternity testing: Why it is not possible for women to tell who fathers their children — Expert

There are several erroneous conceptions about paternity and paternity testing especially in developing nations of the world. In this interview by VERA ONANA, Dr Tolulope Adewole, who is the Executive Director, PathCare Nigeria Limited, Lagos, and a Consultant Chemical Pathologist and Metabolic Physician, debunks the general misconceptions surrounding DNA testing in Nigeria, among other issues.

Recently, there was a case in a Customary court where a lady slept with four men but couldn’t say for sure who impregnated her. However, there is a general notion that only a mother knows who the father of her child is? Can we ascertain the veracity of that claim in this situation?

Medically, yes, we can. Parental testing is the use of genetic fingerprinting to determine whether two individuals have a biological parent–child relationship. A paternity test establishes genetic proof whether a man is the biological father of an individual, while a maternity test establishes whether a woman is the biological mother of an individual. This has become more relevant in recent times due to increased rate of divorce, immigration, mutual distrust, loss of family cohesiveness, Western infiltration of the African society and social benefits.

Is it possible for a woman to be able to tell explicitly who got her pregnant based on calculations from period of intercourse?

No

If a mother’s knowledge would suffice, what then is the need for paternity tests?

There is a need for genetic testing, once there is intercourse with multiple partners, to avoid ambiguity. In fact, there was a court case in the US in 2015, where a man was ordered to pay child support for just one twin after DNA test revealed that the other baby was fathered by someone else. This can happen when a woman has sexual intercourse with two men in the same menstrual cycle and the two eggs are fertilized separately by each man.

What exactly is a paternity test and when is it required?

The DNA of an individual is the same in each and every somatic cell. Sexual reproduction brings the DNA of both parents together randomly to create a unique combination of genetic material in a new cell. It is unique for the person. This genetic material is known as the nuclear genome of the individual. When you compare the DNA sequence of two individuals, it can show whether one of them was derived from the other. There are about 16 parameters used in the DNA sequence and the match must be more than 15 to give a 99.99 per cent acceptability. In testing the paternity of a male child, comparison of the Y chromosome can be used. This is done using the PCR (Polymerase Chain Reaction); analysing STR (Standard Tandem Repeat) and VNTR (Variable Number Tandem Repeat); repeated denaturation, hybridization and extension. This produces exponential copies of the DNA of interest and it is achieved by using oligonucleotide primers and thermostable DNA polymerase.

We have heard tales of irregularities in test results. Can you explain the reason for that?

Irregularities on DNA match are seldom reported from a standard laboratory, except from a non-qualified institution without the necessary quality and standards, and subject to human manipulations.

How accurate is a paternity test?

Very accurate. There are about 16 parameters used in the DNA sequence and the match must be more than 15 to give a 99.99% acceptability. So it’s an accurate process.

How long will it take to get a paternity test result?

Within two weeks.

Can a paternity test be done before the child is born?

Yes, it can be done. It can be done pre-natal or post-natal. In pre-natal paternity test, samples include chorionic villus sampling, amniocentesis and maternal blood for SNP Microarray, which is usually done from nine weeks’ gestational age and the use of fetal cell in maternal blood stream (Cell fine DNA)

Is there an optimal age at which the test can be carried out? Can it be done on a day-old baby? How long will a parent have to wait to ascertain a child’s paternity, if in doubt?

We usually say one month so the maternal blood in the child circulation is out. Maternal blood for SNP Microarray (which is usually done from nine weeks’ gestational age and the use of fetal cell in maternal blood stream.

Asides from blood samples, what other samples can laboratory scientists collect for paternity tests?

Apart from blood samples, the following types can also be used for paternity tests: buccal swabs, chorionic villus sample, amniocentesis, cord blood, hair, forensic samples, combs and chewing gum.

What DNA testing options exist if the person in question is deceased, missing, or unavailable?

HLA typing, polymerase chain reaction(PCR), Restriction Fragment Length Polymorphism and SNP Microarray.

How can DNA testing help protect or challenge wills and estates?

It ensures only the true heirs get the estate.

Are there different types of DNA Paternity Tests?

Not different types, but different methods, as outlined above.

What are the greatest challenges an organisation like yours faces in this country?

The major problem is usually legal, court impediment, having monozygotic twins, chimeras, cost and the lack of obvious paternity legislation in Nigeria.

I understand that sometimes, you send blood samples to South Africa for analysis. What is the reason that?

The skills and volume to engage such an investment is not available within Nigeria. However, we are making frantic efforts with our partners to start with acquiring the necessary skill sets and also to have the volume needed for such huge investment. Also, it is very important for people to set their estates in order so as to prevent unnecessary court cases before they die.
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4 aspects of DNA paternity tests you should know about

Is DNA testing the best way of proving biological relationships?

There is no more accurate way of determining the paternity or maternity of a child than comparing the DNA of the child with prospective parents. Previous analysis of blood groups might prove that a particular person was not the parent, but not that they were. DNA screening can prove with 100 per cent certainty that a person is not the parent, and 99.9 per cent+ that they are.

What’s the difference between a paternity test done at home and a legal test?

The test itself is the same in each case. It is ensuring the identity of the person being tested that is the difference. At-Home paternity tests are also known as ‘Curiosity Tests’ and ‘Peace of Mind Tests’, and for that, you can order a kit online and have it posted to you. You collect your own samples yourself.

To do that, you take an oral swab from inside your cheek or that of the person being tested, and send it off for testing. Your kit will include labels and consent documentation, and instructions together with terms and conditions.

With a Legal DNA Paternity Test, however, the samples must be collected by a third party such as a nurse or GP, who will verify the identity of the person being tested. The testing is carried out in the same way, but these steps are essential so that legal proof of the identity of the person providing the sample is established.

How can I choose the best test laboratory?

There are accreditations provided to testing laboratories, so to make sure you are choosing a good laboratory, look that it conforms to the country’s standard. There is no other way to ensure that you will get high quality results. You should also be sure that a full DNA profile is provided for all 21 loci analyzed, and that you are given the statistical probability of paternity. It is not enough just to report Yes or No.

Can I have a paternity test done without a sample from the mother?

A paternity test is designed to identify the father, and this can be done without a sample from the mother. However, in some cases, particularly where gene mutation has occurred, better accuracy can be achieved if a sample from the mother is available. This can often be done at no extra charge, although you may require the consent of at least one recognised parent, so make sure that you have that authority if you are not including the mother.

What samples can be used for the DNA testing?

Any body tissue or fluid that contains DNA such as blood, semen, hair and saliva on, for example, tissues or cigarette butts can be used for DNA testing. The preferred source is the saliva and cells from the inner check obtained from buccal swabs, but if the suspected parent is unwilling to provide a sample, other sources of DNA can be used.

Additional information from easy-dna.com