In the gene therapy trials for SCIDS, what DNA was added to the patients’ cells? Could this same procedure be used to treat a dominant disease – why or why not?  What are some other options?

"Severe combined immunodeficiency" (SCID) is an X-linked disorder of the immune system that occurs almost exclusively in males. 
It is generally known as "bubble boy disease" because affected children have no functional immune system and are forced to remain in sterile environments to avoid infections. SCID is a recessive condition.

The cause of SCID-X1 is loss-of-function mutation of a gene called IL2-RG, which encodes a protein (gamma chain) that supports the development of several different kinds of cells in the immune system.

Gene therapy of such recessive disorders involves obtaining immune system precursor cells from the bone marrows of the patient and then infected these cells with recombinant retroviruses that contain a wild-type (normal) copy of IL2-RG. Patients administered the altered cells recovered immune system function and were able to resist infection.

Gene therapy for the recessive disorder is a process in which a normal gene was transferred into the defective white blood cells