The steps are as follows:The desired gene is isolated by 'cutting' it out using a restriction enzyme. The same restriction enzyme is then used to 'cut' a vector (plasmid or virus). These can either be left as sticky ends (having exposed unpaired bases) or blunt ends (no unpaired bases exposed).If a process is used that has sticky ends, the ends of the desired gene and vector are complementary.
The isolated genes are incubated with the vectors. If the vectors take up the gene, complementary base pairing takes place. Using DNA ligase ensures the sealing of these bonds which form a phosphodiester link.This isolated genes can also have antibiotic marker genes inserted which can be used to identify the vectors that have taken up the gene.The process forms a recombinant DNA molecule