Y Chromosome DNA Tests
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Test Details
This test is used for establishing whether 2 or more individuals belong to the same paternal line. Women cannot be tested directly as they do not possess a Y Chromosome.
The price includes:
2 Individuals (Males Only)
The cost of the test also includes: Sample collection, all reports and correspondence.
Additional test participants should be charged at the rate specified.
The Y Chromosome Test Explained
A chromosome is basically DNA that is coiled up very tightly. The X and Y chromosomes determine the sex of an individual. Women have two X chromosomes and men have one X and one Y.
At conception a female child randomly receives a copy of either of her mother’s X chromosomes and she also receives a copy the X chromosome belonging to her father.
A male child also randomly receives a copy of either of his mothers X chromosome but this time receives a copy of the one and only Y chromosome possessed by his biological father.
Due to this, the Y chromosome is passed on intact to any male offspring, therefore the Y chromosome passed on by a biological father to his son is exactly the same (except for random mutation) as the Y chromosome he received from his father. He in turn received it from his father and so on. In addition, the Y chromosome of biological brothers, paternal uncles and male cousins will also be identical.
The test analyses 12 genetic locations on the DNA strand. The allele (alternating form of DNA) at each location is identified by a number. Males that are linked by a paternal line should produce a DNA Profile (list of numbers) that match at all the locations tested.
Test Limitations - Mutations
Mutations occur randomly along the DNA molecule. It is extremely rare to see these mutations in the region of DNA analysed during a DNA test, however it is possible.
When a mutation does occur, it will cause a mismatch between the test participants.
One inconsistency in a Y Chromosome Analysis Test will be deemed as a mutation, when all of the other locations match exactly.
Two inconsistencies will be classed as an INCONCLUSIVE result. This is extremely rare.
Three or more inconsistencies will be deemed a negative result i.e. the males do not come from the same paternal line.
Existence of other potential paternal relationships
Examples of when the test should be used:
When all participants in a test are Male, this test may provide more information than the Sibling or Grandparentage analysis.
Case 1: Two men who believe they may share the same father, when the potential father is not available for testing.
Case 2: Grandparent analysis, where a male child wants to establish who his biological father is, by testing his PATERNAL grandparents (i.e. the parents of his biological father) This test would then compare the childs Y chromosome with the Y chromosome of his potential grandfather.
Case 3: A female wants to prove a biological relationship to a living male. e.g. she believes the male to be her uncle’s (father’s brother) son. Females cannot be a DNA source in these tests because they do not possess a Y-chromosome. However, if the female has a brother or other closely related male (from the paternal line), the potential cousins Y Chromosome can be analysed against theirs. In this way, the female can still benefit from a Y-chromosome study.
Case 4: Y chromosome analysis can also be used to assist families that emigrated from one country to another during the past 300 years. Over the years the trail of paper proofs becomes more difficult to find or they no longer exist. This test can prove a biological link between families.
What does the test NOT show?
The test result will not give a conclusion on the nature of a paternal relationship if the Y chromosomes match OR give a reason for a mismatch. It can only tell the clients if their Y Chromosomes match and thus whether a paternal lineage exists between the two individuals.
Clients should be made fully aware of the limitations of the test before proceeding.
For Example:
-
Case 1 - a negative result means they do not have the
same father. However, the result will not say who the
biological father of each test participant is. A
positive result will demonstrate that the two men have a
common paternal line, but it will not conclude that this
is their biological father. This is because the
potential father’s brother, father, uncle etc,
all share the same Y Chromosome. It is not within the
parameter of the test to rule individuals out.
Therefore, in both scenarios, it will be for the Client to decide what the result means to them taking into account the facts and circumstances surrounding the test. -
Case 2 - a positive result will demonstrate that the two
men have a common paternal line, but it will not
conclude that they are grandfather and grandchild. A
negative result means the paternal line does not exist
– however, the test cannot show where the paternal
line was broken i.e. it cannot prove that the alleged
father was actually fathered by the grandfather being
tested.
Therefore, in both scenarios, it will again be for the client to decide what the result means to them taking into account the facts and circumstances surrounding the test.
When should the test not be used?
- If women are involved in the test e.g. A sibling test for a potential brother and sister. Women do not possess Y chromosomes!
- When other paternal links would make the result unclear. e.g. If a test participant was trying to establish who his biological father was by testing a potential paternal grandfather, but the man being tested could either be a grandfather or second uncle to the child in question. This would occur if the potential fathers in a case were paternal cousins! (i.e Second Uncle = Brother of the potential grandfather. Second potential father is son of second uncle, so cousin of first potential father. ALL these individuals would have identical Y - Chromosomes)
In scenarios such as this – a Y Chromosome analysis will not provide the client with any information.