Paternity For Life

Paternity For Life

Understanding Your Results

At Paternity For Life, we understand that for many clients, this will be the first time they have undertaken DNA testing. Please contact us if you have any questions regarding your results, or wish to know more about your results.

Understanding the Paternity DNA Test Report

We each have 2 copies of 22 chromosomes in our body. When an embryo is made, one chromosome is passed on from the mother and the other from the father. Then there are the sex chromosomes, either XX for a girl or XY for a boy. This then gives 46 chromosomes in the embryo.

To establish paternity, we look for markers at specific places on these chromosomes in the child, and then we look for matching markers in the mother and the alleged father. The markers will have a number which relates to the size of the marker. We look for matches, and call these Matching Alleles. As half of the child’s DNA will have come from the mother, the other match will come from the biological father. If the profile does not match, the tested man can be excluded as the biological father of the child.

We test 25 special markers and use matches between the markers from the child and the alleged father to determine whether that tested man is excluded or not excluded as being the father. To be the biological father, there must be a match with 25 markers.

There are two possible outcomes in a DNA paternity test.

Exclusion – THE PERSON TESTED IS NOT THE BIOLOGICAL PARENT. A report which states a paternity exclusion will show a minimum of 2 or more of the numbers in the Matching Allele column that are left blank. When an exclusion is indicated, the probability of parentage is 0%.


Paternity Inclusion – THE PERSON TESTED IS ACCEPTED AS THE BIOLOGICAL PARENT and the report says NOT EXCLUDED. The Probability of Paternity number shows the number of individuals in the population that would have to be tested who may have a profile the same as the tested person


We also calculate a Probability of Paternity. This is the percentage likelihood that a man is an identical match to the alleles of the child. This means there is a very high (greater than 99.9999%) chance of the alleged father being the father. It is never possible to prove 100% that a man is definitely the biological father of a child, as there is always a chance, however remote, that another man in the population may have DNA types which match that child.

Understanding the Extended Relationship Testing Report

Unlike Paternity or Maternity testing, Extended Relationship Testing cannot give a conclusive result of whether or not a relationship exists between the persons being tested. This is because Extended Relationship tests involve comparing less direct relationships than that of a parent and child. A child will inherit 50% of their DNA from each parent, allowing for a conclusive result to be given in the case of Paternity of Maternity. Extended family members, such as aunts, uncles and grandparents will share a lower percentage of DNA with nieces, nephews or grandchildren.

Instead, the results will show the likelihood of a relationship between the tested persons.

  • A likelihood ratio less than 1 – a relationship is unlikely to exist.\
  • A likelihood ratio greater than 1 – It is likely that a relationship exists. The greater the number above one, the greater the likelihood the persons tested are related.

Paternity For Life advises that the results may be inconclusive for an Extended Relationship test. This is not due to laboratory error, but due to the difficulty in comparing individuals in extended relationships. The more degree of separation between two individuals, the less DNA is shared between the two and the harder it is for our extensively validated tests to distinguish two related individuals from the general population and therefore is more likely to produce an inconclusive result. Paternity For Life does not recommend this testing in cases of more than 3 degrees of separation.

**Please note: No testing costs will be refunded in the case of an inconclusive results.

A possible mutation was observed in my child, do I need to be concerned?

Short tandem repeats (STRs), are short tandemly repeated DNA sequences that involve a repetitive unit of 1-6 base pairs. STRs are found throughout the human genome, accounting for about 3% of the entire genome.[1] Most STRs are found in the noncoding regions, while only about 8% locate in the coding regions.[2]

The short tandem repeats (STRs) used in our genetic analysis to determine parentage are in noncoding regions of the DNA. Noncoding DNA does not provide instructions for making proteins. 

STRs are used for paternity testing as they are highly polymorphic (variable) amongst people and can be used to discriminate between unrelated individuals, however, have a higher mutation rate than other regions of DNA, such as the coding regions. In STRs, as with any genetic region, a change (or mutation) can occur in the DNA causing genetic variation. Changes (or mutations) in STRs in noncoding regions are not expected to cause disease. 

When conducting parentage testing the child’s DNA is matched to the alleged parent as the child will inherit one allele from each biological parent. A direct match between the biological parent and child should be found at each locus tested. Where a direct match is not observed, the locus is assessed for a possible mutation. Inherited changes (mutations) from a true biological parent usually show an increase or decrease of one repeat unit. In this case an assumption of a probable mutation between the alleged father and child is made and used in the calculation of the probability of paternity. In such cases a comment will be made on the report regarding the assumption made of a probable mutation. 

  1. Fan, H. and J. Y. Chu (2007). “A brief review of short tandem repeat mutation.” Genomics Proteomics Bioinformatics 5(1): 7-14.
  2. Ellegren, H. (2000). “Heterogeneous mutation processes in human microsatellite DNA sequences.” Nat Genet 24(4): 400-402.

Counselling Options

DNA testing can be a highly emotional process for everyone involved. In some cases, people will have a relationship confirmed which can help to eliminate thoughts of uncertainty surrounding relationships. In other cases, the results may show that a person who you believed was related to you is not related to you in a biological way. The results from DNA testing provide conclusive evidence of a biological relationship and may not always reflect the established cultural relationships between you and the persons being tested.

These results can directly impact the persons being tested, but may also affect other family members and friends of the individuals tested. Results may be life-changing and some people may find it difficult to understand how the family structure will change following DNA testing. Paternity For Life recommends that all persons involved in DNA testing seek counselling both prior to testing and after receiving results.

Children involved in DNA testing should have the testing explained to them and why it is being done. Counselling is recommended before testing is done, as it can be important in maintaining an ongoing relationship with the child. Further counselling is also recommended if the result of a paternity test is unexpected, or believed to have had an emotional impact on the child. Counselling by someone outside the family is sometimes easier for the child rather than discussing the issues with the immediate family members.

Paternity cases before the Family Law court will have counselling options available to them. For cases not before the court, counselling assistance can be accessed at the following sites:



Paternity DNA Testing Lab

Site Design, SEO, SEM and Management by Optimised