Genealogists make use of three types of DNA tests, all of which have their strengths and limitations. Autosomal These popular tests test the autosomes (i.e. not the sex chromosomes) meaning that in any given individual this DNA is effectively an equal blend of each parent. As the amount of DNA from any given line decreases with each successive generation, it is unlikely to show relationships beyond around five or six generations. However, this can be used to our advantage to give an indication of how closely (or distantly!) a match is related. The test is not gender dependent. Y-DNA This tests the Y-chromosome which means that it can only be taken by biological males. The Y-chromosome is passed intact from father to son, with occasional copying errors occurring. For this reason, it can detect male-line (i.e. patrilineal) relatives from very early times, and as surnames often follow the male line, it can be used to identify related branches within a particular surname. Mitochondrial DNA is passed from a mother to all her children, male and female. It is not passed on by fathers, so can be used to identify matrilineal relationships. It mutates extremely slowly, meaning that even perfect matches can be based on a common ancestor who lived a millenium or more ago. It is useful if you wish to determine geographic origin of your maternal line or to confirm/deny maternal lineages. Males with patrilineal Gudgeon origins are encouraged to take a Y-DNA test and funding may be available in some cases.