Assume that you are trying to insert a gene into a plasmid. Someone gives you a preparation of genomic DNA that has been cut with restriction enzymes X. The gene you wish to insert has sites on both ends for cutting by restriction enzyme Y. You have a plasmid with a single site for Y, . but not for X. Your strategy should be to a.insert the fragments cut with restriction enzyme X directly into the plasmid without cutting the plasmid. b.cut the plasmid with restriction enzyme X and insert the fragments cut with restriction enzyme Y into the plasmid. c.cut the DNA again with restriction enzyme Y and insert these fragments into the plasmid cut with the same enzyme. d.cut the plasmid twice with restriction enzyme Y and ligate the two fragments onto the ends of the DNA fragments e.cut with restriction enzyme X. cut the plasmid with restriction enzyme X and then insert the gene into the plasmid.

Plasmid may be defined as the extra chromosomal DNA present in bacteria that can replicate independently of the chromosomal DNA. Plasmid can be inserted from bacteria to another bacteria.

The restriction enzymes are used to cut the plasmid and the insertion of the desired gene into the plasmid to obtain the desired product. The plasmid do not have insertion site for X as shown in the question. This can be overcome if the DNA is cut again with Y enzyme as this will create the common site for plasmid and the DNA fragments that contains the portion of X gene can be inserted into plasmid.

Thus, the correct answer is option (c).