 However, DNA tests are equally important for the two sexes (see genealogical DNA test).Because surnames are passed down from father to son in many cultures ("patrilineal"), and Y-chromosomes (Y-DNA) are passed from father to son with a predictable rate of mutation, people with the same surname can use genealogical DNA testing to determine if they share a common ancestor within recent history.When two males share a surname, a test of their Y-chromosome markers will determine either that they are not related, or that they are related.