複選題25. Gene targeting technologies have many applications, including (A) inactivation of a gene locus by targeting gene disruption. (B) replacing a wild type allele of a gene at one chromosome with a desirable mutant allele. (C) to fuse a green fluorescent protein DNA sequence in frame after a gene of interest. The expression of resulting GFP fusion protein could be used to study how the gene of interest is regulated in vivo. (D) to express Cre recombinase in a tissue specific manner by inserting Cre recombinase coding sequence downstream to a tissue specific enhancer sequence in genome (E) none of above