Final answer:
To clone a gene, restriction enzymes must target specific sites within the plasmid that typically lie within selective marker genes. The resulting sticky or blunt ends permit foreign DNA to anneal to the plasmid, and DNA ligase secures the fragments, creating a recombinant DNA molecule that can be further studied.
Step-by-step explanation:
To clone a copy of a gene, the restriction enzymes must cut at a specific location called a restriction site within the plasmid that is not crucial for its replication. When working with recombinant DNA technology, these enzymes generate sticky ends or blunt ends on both the plasmid vector and the foreign DNA to be inserted, ensuring they can anneal to one another. Following this, the enzyme DNA ligase is employed to 'glue' the annealed fragments together, thereby creating a recombinant DNA molecule that includes the gene of interest.
Typically, the restriction site is positioned within a gene that is used as a selective marker, such as the lacZ gene, which is necessary for metabolizing lactose. If the insertion of foreign DNA disrupts this marker gene, it provides a convenient method for identifying cells that have successfully incorporated the gene of interest. This method is pivotal in genomic libraries where various clones can be screened to find and further analyze the one containing the desired gene from the original organism's genome.