Joe Hart gives a brief tutorial on what DNA testing can and can’t do in helping to track down people you’re related to. He says that Y Chromosome testing works on the direct male line over centuries. He reports Autosomal Chromosome testing is the most popular, dealing with attributes like what you look like, and also somewhat useful in tracing female lines. Its drawback is it only goes back about six generations. According to Joe, Mitochondrial DNA testing has some value in tracing female lines, but is third in utility for genealogical research.