To Study Gene Function, Scientists Use Various Methods to Disrupt

To study gene function, scientists use various methods to disrupt the sequence of the gene.In some cases, this is not possible and conditional knockouts must be used instead.Which of the following statements about the Cre-Lox system for creating conditional knockouts is TRUE?

A) Conditional knockouts can be produced because the gene of interest is flanked by LoxP sites only in the cell type of interest.
B) Conditional knockouts can be produced by expressing the Cre recombinase gene only in the cell type of interest.
C) The gene of interest is not expressed in the cell type of interest in a conditional mutant because Cre recombinase acts to inhibit RNA polymerase when it binds to the LoxP site.
D) Nontarget tissues do not have the Cre recombinase gene, and thus do not produce Cre recombinase.