Y Chromosome
Y chromosome DNA (Y DNA) is inherited along the paternal line, from father to son only (females have no ‘Y’ chromosome). This kind of DNA testing can be used to determine the relatedness of males only.
Y DNA testing ‘decodes’ a list of markers in a sample of DNA. These markers are then compared to other samples to determine relatedness. The greater the number of markers tested, the more accurate the results will be, particularly when revealing relatedness that goes back more than one generation in genealogy.
In the event the potential father is unavailable for paternity testing or is deceased, a male child can submit a DNA sample to be tested against samples from male relatives of the potential father – an uncle (his father's brother) or any other male from the potential father’s male line.
Y-chromosome testing is sometimes used to establish relatedness between siblings if both children are male, to determine whether they have the same father.