By Dr Parker, Chartered Biologist and Member of the Institute of Biology

Earlier this year, the president of Paraguay – Fernando Lugo – announced that he fathered a child whilst he was a catholic priest before he was elected to lead his country.

There are now further claims that he has fathered many more children, but while he has accepted that he is the father of at least one child, he may now need to turn to DNA fingerprinting to determine if he is the biological father to these new claims.

DNA fingerprinting, however, is not as accurate as once thought. Depending on the actual technique used and laboratory protocols, DNA mistyping can occur. You may be surprised, but all laboratory-based processes are prone to errors, and laboratory error rates can range from 0- 25%.

DNA fingerprinting is no exception. The main difference between DNA testing laboratories and other laboratories, such as medical labs, is that they do not reveal error rate for individual DNA laboratories or release any information concerning the precise details of DNA typing processes to you. An example of a possible error within a DNA testing laboratory can be shown below using the scenario of John and Maria.

John had a casual relationship with Maria and this resulted in a child – James. The DNA fingerprint at one genetic site may look like this. Every child receives half of its DNA material from the father and the other half from the mother. James has two DNA bands, one band matches with that of the father (John) and the other band matches with that of the mother. If this is repeated over several sites on the DNA molecule, and the results are similar then John is the father.

If Maria was engaged in another relationship, with a person named Paul, at approximately the same time as John, then the DNA fingerprint could be like that. Thus, if this was repeated over several sites, then it becomes very difficult to assign the true biological father between John and Paul.

James’ DNA band matches with both John and Paul, even though Paul’s DNA band is fainter. Thus assigning the biological father could be attributed to a simple error or possibly be abused. Further tests are required to distinguish the true biological father of James. DNA laboratories do not often repeat their DNA tests to establish reliability of results because of economic factors. This problem of DNA mistyping is not confined only to fathers; sometimes it can occur for mothers as well.

During the 1990s, when DNA fingerprinting was first used to settle paternity issues in the UK, this led to a number of suicides and protests concerning the DNA typing and financial arrangements, which was unnecessary because the technology was in its infancy and had technological faults of which some exist today.

Like many of us, we all make mistakes throughout our lives, including that of President Lugo, who has acknowledged that he is the father of the child William, whose mother is Viviana Carrillo. However, he should be very cautious to other claims that he fathered other children, but also to DNA fingerprinting techniques, because there are errors in this technology.

Dr Parker has just written a book titled 'Errors, Systematic Errors & DNA', published by Parkers Press. For further information, go to www.drpdna.com.