Amelogenin Sex Gene Analysis in Paternity DNA Testing

08 Jul 2017

DNA paternity testing is just one of the many available relationship tests. The rapid growth of DNA testing is fuelled by the great success and reliability of such tests.  Biological links between people can be established accurately only through the scientific means available through these tests.

DNA paternity tests identify specific genetic markers on the DNA samples of the alleged father, the child and often the mother. The genetic markers are compared between the individuals involved and a statistical probability of paternity is calculated. The number of genetic markers taken by the better laboratories will be 21. However, out of these 21 markers, one is the amelogenin gene and is not taken as a marker for comparison between the DNA profiles of individuals involved.

 How is Sex Determined?

Chromosomes determine the sex of an individual. A male individual will have a pair of XY chromosomes with the Y-chromosome specifically determining maleness. On the other hand, females will have a pair of XX chromosomes. The amelogenin gene is found on both the X and the Y chromosome. Size differences in the amelogenin gene on the X chromosome and Y chromosome is used to differentiate the sex of the DNA samples provided.

 Why test this Amelogenin Gene?

There are a several reasons for testing this gene which shall hereunder be explained.

In standard DNA tests, for example a DNA paternity test, the testing of this gene is a quality control measure that ensures correct samples are being processed and that results are reliable. Sometimes clients might put the wrong swabs into an envelope, this can be done by mistake or sometimes clients do it deliberately, hoping to alter the results. In forensic DNA tests the analysis of the amelogenin sex  gene is also useful as any remains found that are beyond recognition can be identified as belonging to a male or a female by testing this gene through samples of bone or other tissues remains. In some cases, there can be a mix of DNA samples on a crime scene and investigators will want to determine of what gender these DNA samples are.

Finally, in infidelity DNA testing scientists will also test for this gene to know whether DNA stains sent for testing belong to a male or female.

Problems when Testing the Amelogenin Sex Gene

In very few and far between cases, analysis of the amelogenin sex gene can generate false results. In such cases, male DNA samples appear to be female.  What happens from a genetic perspective is that there is no amelogenin gene present on the Y-chromosome; a phenomenon known as deletion. The gene will only be present on the X-chromosome and therefore, samples submitted in a DNA paternity test for a male may appear to be female. The incident rate of this deletion is however miniscule and happens in about 0.001% of DNA analyses.