Did you know Y-DNA STR testing is useful for forensic, relationship and genealogy testing?
Detecting recent changes in your Y-DNA
You’ve always been proud of your rather unusual last name. One day, another man with the last name Quigley sits beside you on the plane, and you are intrigued. A long conversation during the flight reveals that both of your great-great grandfathers immigrated to North America from Northern Europe. You both agree that you might be related. At the end of the journey you exchange contact information and go your separate ways. Even a couple of weeks later, you are still wondering, “Could I be related to this other Quigley?” There is a simple test that can solve this puzzle and it’s known as a Y-DNA STR marker test. It helps individuals to track their paternal lineage, and find close and distance relatives on their paternal line.
DNA paternal ancestry testing involves examining markers on the Y-chromosome (Y-DNA). Geneticists examine two types of markers found in the Y-DNA. One test detects extremely slow changing markers called SNPs (single nucleotide polymorphisms). The drawback of Y-DNA SNP tests is that it can only provide information on an individual’s ancient ancestry, but it will not provide any information regarding more recent ancestral events.
For two males wishing to determine whether they share the same recent paternal lineage, a different group of markers known as STRs (short tandem repeats) must be used. STR markers are small DNA sequences, 2 to 13 nucleotides in length, which are repeated many times in a row. STR markers have a much faster mutation rate compared to SNPs. This rapid mutation rate is useful for tracing more recent ancestry, such as searching for males with common paternal ancestors within the past 500 years.
We each inherit 22 autosomal chromosomes and one sex chromosome (X or Y) from each of our parents. Both men and women inherit an X-chromosome from their mothers. Daughters inherit a second X-chromosome from their father, and sons inherit a Y-chromosome from their father. This means, STRs on the Y-chromosome are passed down strictly from father to son, and can be used to trace the paternal lineage. Maternal ancestry can also be traced through a different analysis of mitochondrial DNA.
Surnames are passed down from father to son in many societies. Therefore, Y-STRs tests are the best choice when trying to determine kinship between people with the same last name (such as the two Quigleys), or searching for relatives who descended from the same paternal line. Comparing the Y-STR profiles of any two individuals determines if they descended from the same forefather. It also indicates approximately how many generations ago any two men shared the same paternal ancestor, based on the “time to most recent common ancestor” (TMRCA) calculation.
The TMRCA value is based on the mutation rates of STR markers, the number of STR markers compared, and the number of matching STR markers. So with just a simple mouth swab and Y-STR test, the two Quigleys can quickly determine if they descended from the same forefather. Also, if they are choose to use existing ancestry databases, they will be able to search for individuals from around the world who have also descended from the same paternal lineage.
Whether you were adopted with no information about your biological parents, or someone wishing to research your family history, Y-STR testing is a good starting point to trace your paternal ancestry. Once you find your first few matches, you can use those matches as a lead to investigate further. If you are the family genealogist you can use Y-STR tests for confirming family legends, solving family mysteries, and searching for new family links. The Y-STR marker profiles of many notable figures in history have also been determined. Hence, if you just want to know whether you are linked to famous men (like Thomas Jefferson, Genghis Khan, or King Ramesses III), Y-STR tests can find those links.
Y-STR marker testing is not only useful for genealogy, but is also used in solving relationship questions and forensics. While both paternity testing and forensic analysis rely on STR markers on the autosomal chromosomes, there are special circumstances when STR markers on the Y-chromosome become useful. In the case of unknown paternity of a male child where the assumed father is deceased, Y-STR testing from living paternal line descendants can be used to provide evidence of kinship. In forensics, Y-STR marker testing is used when dealing with mixed samples. Because females do not have a Y chromosome, all contaminating female DNA can be excluded from the tests. Y-STR marker testing was used to help solve the Boston Strangler case 50 years after the crime was committed.
The Y chromosome may be the third smallest chromosome, but over a hundred Y-STR markers can be tested that are useful for paternal lineage analysis. The one caveat is that only men can take this test, as only men have a Y-Chromosome. Females wishing to investigate their direct paternal lineage must test the Y-DNA of a direct paternal line relative, such as a brother, father, uncle or cousin. Whether you choose to take the Y-STR test to answer relationship questions, search for paternal relatives, or investigate matches to famous people in history, Y-STR markers are the one of the fundamental genetic markers for beginning the investigation of your paternal lineage.