A couple comes into your genetic counseling practice with a question about the chance a future child of theirs might have a genetic disease. Three or four men in the woman's family, including her father, had a condition that might be genetic. Although her father is still alive, she has had little contact with him for much of her life and cannot describe or name the condition. Her partner is a healthy man whose family has no history indicating the presence of a genetic condition. To provide more information about this possible genetic condition for the couple, what is the first step you recommend?