No you're not only giving them your DNA. You're minimally giving them your e-mail, first name, last name, credit card info and I assume home address. That is all someone needs to do damage because it's all in the same database. Farming fingerprints and trying to match them to banking information would be a ridiculous waste of resources and no hacker would do that.
Ancestry uses your DNA sample to collect information about your family history in a single profile. That profile now becomes a one-stop shop to steal lots of information about you.