How DNA will tell if Happy is Jannie

Is Happy Sindane and Jannie Botha the same person? Blood tests are being done to determine whether this may be true. In South Africa the latest technology is available and paternity tests using DNA are done with great accuracy.

High accuracy rate of paternity tests
So, how accurate are these paternity tests really? Is it really possible to say with 100 percent accuracy that that a specific man or woman is a specific child's father or mother? And is it really possible to say with 100% accuracy that a certain man is not the father of a specific child? Absolutely yes. With the help of the right tests, scientists can provide an accurate answer.

According to Professor Ernette du Toit, head of the Western Cape Tissue-immunology Laboratory at Groote Schuur Hospital, the real father or mother can be identified very accurately, as can the falsely-accused supposed father.

With the help of accurate DNA tests, the real father or mother can be identified, and no falsely-accused man will have to pay for the wild oats sown by the real father.

Who wants to know about paternity?
Paternity may be questioned in many cases. In many cases the courts require these tests when there is a question mark over the paternity of a child in a maintenance case. The aim of these tests is to determine paternity or to rule out a candidate as the possible father of a child. In some cases a man wants to know whether he is indeed the father of the child, or he wants to prove that he has been falsely named as such.

Or in this case, DNA will be used to determine if Happy is indeed Jannie or not.

Health24 asked Professor Du Toit en Veronica Borrill (chief medical technologist) exactly how these tests are conducted.

Blood tests
Blood is taken from the mother, the baby and the supposed father according to a specific procedure, so that there could be no doubt that the blood is indeed that of the three people involved. It is double-checked that the tubes are correctly marked.

Three possible tests can be done on the blood or tissue samples to determine or rule out paternity.

The HLA antigens are compared, the DNA (and specifically eight different short tandem repeats) is compared, and the blood groups can also be compared. Two of the three tests can deliver a very accurate result regarding the paternity of the child, and can determine both whether someone is indeed the father of the child, or can rule him out as the possible father.

The principles of all three tests are the same:
A baby gets half of its antigens from its mother and the other half from its father. If the baby has antigens that could not have come from the father, the man in question cannot be the baby's father.

What is being compared?
The HLA-(Human Leukocyte Antigen)-locus on the white blood cells of the htree people are compared. The HLA-locus is the place on the leukocyte (white blood cells) onto which specific antigens bind.

Die HLA-A-locus carries A-antigens, the B-locus carries B-antigens and the C-locus C-antigens. In every population group specific antigens are found at a certain frequency.

It is furthermore kept in mind that a baby may possess certain antigens because a certain percentage of people in specific population groups have these antigens. The probability that a specific man is the father of the child, is determined according to a probability index. If two or more of the antigens of the child correspond with those of the father, the chances are very high indeed that that is the father of the child. If the child has no antigens that correspond with those of the father, the chances are zero that he is the father of the child.

The DNA test
Eight different short tandem repeats in the DNA are compared. The repetitions appear in pairs. The baby gets half of his pair from his mother and the other half from his father. If the baby has two or more repetitions which the father doesn’t have, there is no chance that the father can be the father. If half of the baby’s repetitions correspond with eight of the mother’s and the other eight with the man’s, the chances are 99.88% or greater that the man is the father.

Blood groups
Blood groups, together with the DNA test or the HLA test, are used to determine paternity.

If a baby has genetic material which does not come from the father in two of the loci in two different tests, the chance is 100% that the man is not the father.

The test of blood groups is the simplest method but the chance of exclusion is only 50%. The mother’s, baby’s and father’s blood groups are compared according to the ABO blood groups as well as according to the Rhesus factor, the MNS, Kel and Duffy-groupings.

Why are blood groups alone not so accurate?
If a mother belongs to blood group A, she can have two A-antigens or an A and O-antigen. If the father belongs to blood group O, he can only have two O antigens. The baby can therefore be either A (an A from the mother and an O from the father) or O (an O from the mother and O from the father). If the baby is AB, one knows that there is something fishy because how does one explain where the B comes from?

Paternity tests for mother, baby and father cost approximately R2 000. The most accurate paternity tests are HLA and DNA, or DNA alone, but then far more than only eight tandem orders.


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