As more people have their DNA tested and as the results databases grow, you will have an increasingly better chance of connecting with your birth father by genetic means. While it is true that you are unable to trace your father's identity through his Y-DNA (the traditional male paternity signature) because a female does not inherit it, do not despair: There is another method. Autosomal DNA testing looks at the 22 pairs of chromosomes that do not determine gender. This can be very useful in identifying relationships within five generations of yourself, without being limited to only maternal ancestors.
It is true that your results will be most useful if your biological father or one of his close relatives (preferably his brothers or sisters or his first cousins) also had genetic data registered with the DNA testing company you use. Companies like23andMe (through DNA Relatives) and Family Tree DNA (through Family Finder), as well asAncestry.com and Genographic, can compare the data from these autosomes for shared segments. You should take tests with each of these companies as their databases are proprietary -- that is, they are not shared or overlapping.
The closer the genetic relationship you have with a person in one of these databases, the more identical segments of DNA you will share. And these companies even determine, through the lengths of these segments, if you have a brother or sister in the databases or, indeed, if you descend from a parent. But we stress that this is a very long shot.
According to the 23andMe website, "DNA Relatives uses the length and number of these identical segments to predict the relationship between people." If your birth father himself has contributed his DNA results, you will be able to tell [if] he is your father. A 30 percent to 40 percent match with someone probably indicates that the person is your half-sibling. 23andMe and Family Finder both display predicted relationships between you and the people whose DNA aligns with yours to some degree. This means that by submitting your DNA results, you would be casting a net and hoping that a relative on your father's side has contributed DNA as well. Should you find any such people, you can contact them through the company you have both joined.