Question

1.When comparing ex vivo and in vivo gene therapy techniques, which of the following statements is true?

A. Ex vivo therapy only relies on bacterial plasmids as vectors, whereas in vivo therapy only relies on viral vectors.

B. During ex vivo therapy, the gene is transcribed (but not translated), whereas with in vivo therapy, the gene is both transcribed and translated.

C. In vivo therapy typically involves the injection of a new gene directly into an individual, whereas ex vivo therapy involves the introduction of a gene into cells first.

D. In vivo therapy involves vectors that do not harbor a promoter, whereas ex vivo vectors always have a promoter region.

2.When performing in vitro mutagenesis, a vector is used that may contain a positive marker (e.g., a gene for resistance against the antibiotic neomycin) and a negative marker, such as the thymidine kinase gene. Cells that carry the latter will die when exposed to a drug called ganciclovir. If a researcher exposed stem cells to a targeting vector with these two markers, and subsequently treated them with neomycin and then ganciclovir, which would be true of the surviving cells?

A. Any surviving cells will have been correctly targeted (i.e., the gene of interest will have been removed).

B. Half of the surviving cells will still contain the gene targeted for inactivation, whereas in the remaining half this gene will have been removed.

C. Any surviving cells will not carry either the positive or negative markers.

D. Any surviving cells will still contain the original, targeted gene (i.e., these cells could not be used to generate knockout mice).

Answer 1

1. The option C is correct. The in Vivo gene therapy uses a new gene, with correct sequence to treat the disease caused by mutated form of it. It's just that in Vivo gene therapy is done in the body of patient while ex Vivo gene therapy is done in the cells grown outside of body. Both of these therapies make use of viral vectors which have active promoters and the genes is transcribed and translated.

2. The cells survived with these two treatments. Neomycin resistance is there in these cells. But the cells are sensitive to other drugs too. Therefore option A is suitable for their fate.