Sticky (cohesive or staggered) ends are hanging ends produced by the restriction enzymes in which the terminal portion has a stretch of unpaired nucleotides, and the strands are not of the same length. The terminals can easily pair up with the complementary strand. For example the sticky ends produced by EcoRI enzyme is given below
These sticky ends are important for genetic engineering to develop recombinant DNA. To make a recombinant DNA plasmid, a restriction enzyme is used to cut both the plasmid and the sticky ends are produced. These sticky ends are ligated to form recombinant DNA. One example of recombinant DNA is creating a plasmid that has ampicillin resistance.