Can mental illnesses such as autism and schizophrenia be passed on to children?

My fiance and I both of family members who suffer from these ailments, my sister has autism, and her mother has schizophrenia. When we decide to have children of our own, is their a higher chance that they might suffer from these conditions? Also, is my soon to be wife at risk of becoming schizophrenic [...] http://bit.ly/n5muQD