Y-DNA STR Marker Test
Common uses for Y-DNA STR Marker Testing:
1. To supplement the results a relationship test, such as a sibling test, grandparentage test, uncle test, or cousin test
While DNA parentage tests (paternity test and maternity test) can always provide an absolutely conclusive result regarding parentage, other relationship tests types are not as discriminating as the DNA parentage tests. DNA Sibling tests, Grandparentage tests, Aunt/Uncle tests and Cousin tests are usually only ordered when the parents are not available for testing and there is no other choice but to test other relatives. If a kinship test is performed and the result is not conclusive enough, Y-DNA STR testing can be considered as a supplemental test type for the kinship test. All males who have descended from the same paternal lineage will have the same Y-DNA STR profile. If two males do not have the same Y-DNA STR profile, it would conclusively confirm that they are not related along their direct male line.
Here are some examples of situations where a Y-DNA STR marker test may assist in supplementing a relationship test:
a) To check the relationship between a grandson and a grandfather
If a Grandfather test between an alleged grandfather and an alleged grandson does not provide a conclusive result, testing the Y-DNA of both individuals to see if it matches can provide further confirmation. If the alleged grandfather and grandson have completely different Y-DNA STR profiles, it will conclusively confirm that the alleged grandchild is not the true biological grandchild of the grandfather.
b) To check whether two brothers have the same father
If a sibling test between two alleged brothers does not provide a conclusive result, additional Y-DNA STR testing can be performed. If the two brothers do not have the same Y-DNA STR profile, it will conclusively confirm that they do not share the same biological father.
c) To check whether male cousins have the same paternal grandfather (to see if their fathers are brothers)
If a cousin test between two male cousins who allegedly have fathers who are brothers does not provide a conclusive result, additional Y-DNA STR testing can be performred. If the two male cousins do not have the same Y-DNA STR profile, it will conclusively confirm that their biologial fathers are not brothers.
d) To check whether an alleged uncle (brother of alleged father) is the biological uncle of a nephew
If an uncle test performed between an uncle (brother of alleged father) and an alleged nephew does not provide a conclusive result, additional Y-DNA STR testing can be performed. If the alleged uncle and nephew do not have the same Y-DNA STR profile, it will conclusively confirm that the uncle’s biological brother is not the true biological father of the child.
2. To check whether two male individuals have descended from the same paternal line, even if they are not immediate family members
Males who have descended from the same paternal line will have the same Y-DNA profile, even if they are not immediate family members. Any two males can be tested and compared to see if they possibly descended from the same paternal line. If the test shows that two males have different Y-DNA profiles, it would conclusively prove that they definitely are not from the same paternal line. Since the inheritance pattern of Y-DNA is the same as the pattern in which the surname is passed down from father to son, individuals wishing to see if two males with the same surname are related on their paternal line can also compare their Y-DNA STR markers.