Y–STR Male Lineage DNA Testing

Question

My father died never knowing who his biological father was. His birth certificate has no father mentioned and whenever we speak to his mother who is still alive, she will not reveal any information.

He has a brother in another country who is considered a half-brother, but he may be his paternal brother however I was wondering....

If we were able to get both my DNA and my uncle's DNA sent together to a lab, would Y–STR male lineage DNA testing be able to test with high certainty whether my father and my uncle shared the same father?

Also would getting my uncle to send DNA samples half way across the world pose problems with shipping whilst maintaining viability of a reliable test?

Answer 1

Yes, a Y-DNA STR test would be the ideal test for testing whether two people share the same paternal lineage. I would suggest taking a test with a high number of STR markers (e.g. 67 markers) to be sure of a match. You would expect a person and their uncle to match at a very high number of markers (probably 67/67).

For your uncle to be tested, you would need to have the kit sent directly to his address, and returned to the testing company. People all around the world use testing companies on other continents, so it will not be a problem to ship the test kit over long distances. Typically a test will involve swabbing cells from the inside of your cheek, and then being placed in fluid to prevent bacterial growth and maintain viability while being shipped.

Answer 2

Yes, it will tell you with high certainty. The Y-STR chromosomes used as markers tend to show about 1 mutation (across all markers) every 5-6 generations. So a 100% match generally implies a common ancestor within 5-6 generations, 1 marker off implies a common ancestor within 10-12 generations, and so on.

However, the previous comment regarding using higher numbers of markers is significant - a 12 for 12 marker match probably doesn't mean that there's a common ancestor, just that a test with a higher marker count is needed.

As to long-range viablility, DNA is a remarkably stable molecule (life on Earth pretty much depends on that). Remember that crime labs have done useful (if not exhaustive) DNA tests on samples decades old, and prehistoric mammmoth DNA has survived frozen for over ten thousands years.