She describes this all extremely well. For diseases that are caused by autosomal genes, dominant means that a mutation in one copy of the gene causes symptoms or signs of the disorder. A relatively common autosomal dominant disorder is Neurofibromatosis. In recessive disorders, both copies of the gene must have mutations before there are symptoms. Parents are silent carriers because just one normal copy of the gene is enough to get by without symptoms.
Cystic fibrosis is an example of an autosomal recessive disorder.
For disorders caused by genes on the X chromosome, it gets more complicated. In this disorder, most women with a mutation in one copy of the gene are just fine. Thinking back to XCI, it makes sense. In Hemophilia A, the causative gene directs the production of a protein called Factor VIII that is required for clotting. If the woman has random XCI, then half of her cells are making normal Factor VIII and half her cells are making a protein that does not work properly.