The Rosie project by Graeme Simsion

Don Tillman sets up a project designed to find him the perfect wife. His starts off with a questionnaire that has to be adjusted a little as he goes along, especially once he meets Rosie. Rosie is everything he's not looking for in a wife, but she ends up his friend as he helps her try and find her biological father. Of course it helps that he is a Professor of Genetics so know a things or two about DNA and how to obtain it.