An adapter in genetic engineering is a short, chemically synthesized, double strandedDNA molecule which is used to link the ends of two other DNA molecules. It may be used to add sticky ends to cDNA allowing it to be ligated into the plasmid much more efficiently. Adapters are synthesized such that they have sticky end at one end and blunt end at the other. Two adapters could base pair to each other to form dimers. Adapters are used to link the ends of two DNA molecules that have different sequences at their ends. A conversion adapter is used to join a DNA insert cut with one Restriction enzyme, say EcoRl, with a vector opened with another enzyme, Bam Hl. This adapter can be used to convert the cohesive end produced by Bam Hl to one produced by Eco Rl or vice versa. One of its application is ligating cDNA into a plasmid or other vectors instead of using Terminal deoxynucleotide Transferase enzyme to add poly A to the cDNA fragment.