  The younger Mr. Hill was quickly able to learn who his
biological mother was. But cracking the identity of his birth
father -- shrouded in coverups, lies and false trails -- took 26
years. In the end, Mr. Hill solved the mystery with the help of
sophisticated DNA-based genealogy tests.  For most people who
practice it, genetic genealogy is a hobby. But as the tests grow
more powerful, people are starting to unearth family secrets.
Many offspring of sperm-donor fathers are using Internet-based
DNA searches to locate their so-called biodads. Others hope to
identify unknown family members by connecting DNA profiles with
last names.  In men, the Y chromosome is passed on from
generation to generation, from father to son. So, usually, are
last names. Accordingly, men with a close Y-chromosome match are
more likely to have the same last name. A handful of Web-based
businesses now offer DNA searches for male adoptees. Genetic
searches along female lines are possible, but less effective, in
part because many women