Shortened PCR cycles in a conventional thermal cycler.

step. The presence of Vent DNA polymerase and PCR products other than the intended DNA linker, however, did not seem to interfere with subsequent reactions because ligations using both gel-purified and unpurified PCR products yielded a similar number of transformants. Eight transformants were tested, all of which contained the PCR product as an insert. The yield was considered to have high efficiency, in contrast to the low numbers of transformants obtained by ligase-free cloning approaches (4). Sticky-end PCR generates PCR products as DNA linkers that are ready to clone into vectors bearing compatible sites. Because the method involves only one round of PCR and eliminates time-consuming treatments of the PCR products, such as restriction digestion, it greatly reduces the cloning time. Sticky-end PCR can also accommodate the special needs of certain cases, such as the presence of internal restriction sites in the PCR product.