Which of the Following Is the Best Procedure in Order

Multiple Choice

Which of the following is the best procedure in order to position a gene in an expression vector downstream from a promoter (i.e.,perform directional cloning) ?

A) Use a vector with 2 sites for the same restriction endonuclease.
B) Treat the gene with DNase I.
C) Restrict both the gene and the plasmid with 1 restriction endonuclease,and then screen all colonies for those that express the gene.
D) Restrict each end of the DNA fragment (gene) with a different restriction endonuclease,and do likewise for the plasmid.