Rachael's doing the one thing she said she would never do on the show -- DNA testing to find out "who's your daddy?" But there's a twist -- the tests are being done on a few furry, four-legged friends! Vet Dr. Ernie Ward explains, "We now have tests for dogs that can determine who their mom, dad, even grandparents were -- it's very interesting!" In addition to determining any medical issues your dog might be prone to based on its lineage, the DNA testing helps answer the top two questions mixed-breed pet owners usually have: "What is it made up of?" and "How big is it going it get?"

Joining Dr. Ernie and Rachael to find out what kind of dog she has is award-winning actress Bernadette Peters, who has adopted two dogs from New York City shelters -- a pit bull named Stella and her 9-year-old Kramer. "We don't know what he is," she says. "I think Kramer's breeds are: the ears, Briard; some of the shape of the body and the tail are German Shepherd; and he has a thick undercoat, so he could have some Chow." Bernadette also wonders if Kramer is part of a breed that's susceptible to tumors, as Kramer had to have an eye removed due to cancer.

Bernadette tries the Wisdom Panel Mixed Breed Analysis Kit, which uses a simple blood test to determine Kramer's pedigree. So, who is the dog's daddy? Bernadette is shocked by the results. "Kramer is about 50 percent Golden Retriever," Dr. Ernie reveals, "and about 25 percent Chow Chow, and 25 percent was mixed beyond what we could tell. So one parent was a Golden Retriever, and one grandparent with a Chow." Dr. Ernie explains that cancer is the number one cause of death among Golden Retrievers, so it was a good thing Kramer's eye tumor was removed, but that Bernadette still needs to be on the alert.

Doggie DNA testing is also important for people who are looking to adopt a dog. Dr. Ernie explains, "If you're going into a shelter [to pick out a dog] -- based on your lifestyle, where you live, children and so forth, it's almost impossible [to find an exact match for you]. You go through and you look at these dogs and you wonder, is it going to be big? Is it going to be aggressive? Is it going to be docile? If we could have a test that would say, look, this has the predisposition for these behaviors or traits, traits that would really help with the selection process." Watch the video above to see what happens when one of Rachael's staffers -- who adopted a shelter dog during the filming of the segment -- learns the makeup of her dog Archie.