YOUR GOAL: You are studying how a particular gene, named Insom, might play a role in insomnia. You want to study mice with this gene turned off. To knockout the Insom gene you will A) replace it with a mutated, inactive copy of Insom. B) destroy the mouse DNA with chemotherapy. C) radiate the DNA, hoping for mutations. D) kill the mouse and examine its DNA.

I believe its answer A

Explanation:

because so many mouse genes are similar to human genes, geneticists can generate knockout mice in which the mouse counterpart of a human gene of interest is deleted or disrupted.  geneticists use the term to refer to a mouse that has been genetically engineered such that at least one of its genes is functionally inactivated (i.e. the inactivated gene is "knocked out")