In the Form of Gene Therapy Used Successfully for Severe

Multiple Choice

In the form of gene therapy used successfully for severe combined immunodeficiency syndrome, SCID-X1, how is the genetic engineering of human cells achieved?

A) by injecting engineered viruses into the patient's bloodstream
B) by injecting engineered viruses into the patient's bone marrow
C) by treating a relative's cultured bone marrow cells with genetically engineered viruses and then injecting these cells into the patient's bone marrow
D) by isolating the patient's bone marrow cells, infecting them with genetically engineered viruses, and injecting them back into the patient's bone marrow