In a holiday commercial, Dr. Seuss’s the Grinch receives a 23andMe DNA kit as a gift and logs on to the company’s website to check out his results. He learns he’s genetically likely to move around more than average during sleep and that liking salty snacks is in his DNA. The commercial ends with a voice-over: “This holiday season, give the gift of a DNA kit from 23andMe.com.”

The commercial seems to be aimed at parents and their children. It’s not the first time 23andMe has used popular cartoon characters to market its tests. Last year, it launched an ad campaign around the movie “Despicable Me” and its yellow minions.

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Greely says if kids are really interested in learning about their genealogy, parents should take the tests instead. “You get a better resolution of the ancestry the higher up the family tree you go. You get more details from the parents than you will from the kids and more details still from the grandparents,” he says.

Hank Greely, a bioethicist and director of the Stanford Center for Law and the Biosciences, says he also worries about children misunderstanding health reports. Greely remembers getting a skin test for tuberculosis as a child. The nurse told him his test results were negative. “I was a kid and I thought ‘negative’ meant bad. I thought I was dying of this thing called TB,” he says.