Dear Dr. SerVaas: We are trying to put together a family tree of my husband's family and have come to a standstill because, we believe, the family name was changed some 175 years ago. Our question is: Can DNA testing possibly be done on someone over 100 years after his or her death?

Jill Jackson

Dear Reader: We understand that the ability to conduct DNA testing is determined by the condition of the tissue sample and not its age.

DNA is found in almost every cell of the body except the red blood cell. As a result, testing can be performed on bone and teeth fragments and may be possible on bodies hundreds of years old.