A Guide to Maternity DNA Testing

Guide to Maternity DNA Testing

During a DNA Maternity Test, we analyse different genetic locations on the DNA molecule. A person possesses two (of many possible) alleles at each location. We identify each of these alleles with a number. Inheritance of Alleles comes from the biological parents at conception. One comes from the mother and one from the father.
 
First, we lay out the DNA profiles of the biological parents. Then, we analyse the child’s DNA profile with the mother’s at each location. In turn, one of the child’s alleles (numbers) will match up with a number from the alleged mother’s sample. Next, if these alleles match at all locations analysed, we include a person as the biological mother of the child. This is because it proves they have passed these genetic markers to the child at conception.
 
Inconsistencies (locations where there is NO match) will exclude a person as a biological mother. This is because it is only possible to pass on to your offspring the alleles which you have in your own DNA profile.

Maternity DNA Testing Accuracy

>99.9999 probability obtained for inclusion as a biological parent.
 
This result means that a person is at least 1 million times more likely to be the biological parent of the child tested. This is in comparison to an unrelated individual from the same ethnic group. The percentage probability reported will differ between cases. This is because the calculation depends on the alleles that are shared between the test participants.
 
0% probability obtained when excluded as a biological parent.
 
This result means that there is 0% chance that the person tested is the biological parent of the child.

Inconclusive Results

If we deem your DNA test result as INCONCLUSIVE, it will be due to one or more of the following reasons:
 
Related Alleged Mothers
 
If a close relationship exists between potential mothers e.g. sisters, we will need a sample from all potential mothers. If this advice is not followed, it may only be possible to exclude a person as the biological mother. An inclusion may be dependent on ruling out the second related. This is due to the fact that close relatives have more DNA in common than unrelated individuals.
 
Low Maternity Index
 
The frequency of alleles (numbers) differs within each given ethnic group. Also geographical population plays a part. For instance, some alleles are very common, some very rare. As an example, what id the alleles that match between a child and an alleged mother are ALL very common to their origins? This could lower the ‘Maternity Index’ and the evidence of the result. If this is the case, and even if there is a full match, we will deem the result as INCONCLUSIVE. As a result, we must include either the father’s sample or we can analyse further points on the DNA molecule. This could incur an extra fee but may mean we can issue a conclusive test result.

Genetic Mutations

Although mutations occur at random along the DNA molecule, it is rare to find them within the region of DNA that we analyse. The types of DNA mutation referred to here are not harmful. But they will change the form of an allele in some way. In turn, it will change the number that identifies the allele. The number now assigned to the related location will form part of that person’s DNA profile. Yet the number will no longer match the corresponding inherited allele of the biological parent. We will determine whether the inconsistency is due to mutation or whether it is a mismatch.
 
We will use the number of inconsistencies found and the remaining DNA evidence provided by the test to reach a conclusion. If we need further evidence, then we will report the test as ‘Inconclusive’. In short, because mutations are so rare, we would not class many inconsistencies between DNA profiles as a mutation.