Millions of people across the globe claim Irish ancestry. While everyone is a little bit Irish on St. Patrick’s Day, a growing number of people are interested in testing their DNA to determine just how much of a particular ethnicity comprises what makes him or her unique. Thanks to an array of DNA-testing companies, just about anyone with some disposable income can have a vial of their saliva tested to determine their ancestry. Before one starts toasting to St. Patrick, he or she should understand that these tests are not foolproof. Keep in mind that DNA tests use genetic markers that indicate variations in DNA that one or several ethnic groups may possess. Not all companies test for the same number of genetic markers. User error, namely a saliva sample that is compromised, can also affect results. While many of these tests can provide a general range of a person’s ancestry, they are not 100 percent accurate. As long as testers realize there is a margin for error and seek DNA for fun and curiosity, rather than to prove or disprove a country of origin, the results can be entertaining.