Why is insertional inactivation of an essential gene not likely to be an important risk in retroviral-mediated gene therapies?

Question

Quizplus · Accepted Answer

The likelihood of a retroviral vector inserting into and inactivating an essential gene in a significant number of cells is very low, making it an unlikely risk for gene therapy. Retroviruses integrate randomly into the genome, and the human genome is large, so the chance of multiple insertions into the same essential gene across many cells is small.

Why Is Insertional Inactivation of an Essential Gene Not Likely