Relationship testing

DNA Labs can test for biological relationship for the following circumstances.

Sibship

DNA testing methods can provide information about relationships within a family. An analysis of whether two people (regardless of sex) are full or half siblings can be done. However, unlike paternity testing, which provides very conclusive results, sibship analyses are not as conclusive. If two people are full siblings, mathematically we expect them to share 50% of the genetic markers we test. If two people are half siblings, then 25% of their genes will be common. This principle then allows us to determine statistically the chance that they would share the DNA if they are siblings, compared to if they are unrelated (ie. if they matched by chance - population frequency). It is not possible to determine with 100% certainty whether or not two people are siblings.

Female Relationship Testing - (X Chromosome Testing)

Females inherit two X chromosomes, one from their mother and one from their father. Males have a single X chromosome and a single Y chromosome. Mothers will randomly assign one of their two X chromosomes to each of their children. All the daughters of a man will share his only X chromosome. Extracted DNA samples are analysed at variable or polymorphic sites and compared to distinguish the origin of each X chromosome.

Male Relationship Testing - (Y Chromosome Testing)

Females inherit two X chromosomes, one from their mother and one from their father. Males have a single X chromosome and a single Y chromosome. The inheritance of the Y chromosome is strictly from male to male and will be shared by all male members of a common male predecessor, provided a male line is in place. This testing can be used to establish if two men share the same father. It should be noted that this testing does not distinguish brothers from paternal cousins or sons from grandsons etc.

Extracted DNA samples are analysed at polymorphic sites and compared to distinguish whether the individuals share a paternal line. For this to be true they need to match at each locus.

Mitochondrial testing

This type of testing is used in cases where two potential siblings, male or female, wish to know if they share the same mother.