A few years ago, Angela Evans decided she wanted to test the DNA of her 10-year-old daughter and 7-year-old son. She was interested in knowing whether they had a mutation of the MTHFR gene, as she does. The mutation is linked to a number of disorders — women with the mutation may have a higher risk of having babies with defects like spina bifida — and Ms. Evans wanted to make life changes for her children based on the results.

When doctors told her they didn’t think there was a medical need to test her children, she decided to use 23andMe, the direct-to-customer genetic testing company.

To use 23andMe’s services, the user simply sends in a saliva sample. Within five weeks the company returns the results, without the mediation of a doctor or genetic counselor.

Along with finding out that both her children had a mutation of the MTHFR gene, she also received 23andMe’s analysis of her children’s genetic susceptibility to a number of adult-onset diseases, including Parkinson’s. Ms. Evans shared the results with her children, family members and friends.