Alternatively, a number of new methods of target amplification have been proposed. Strand displacement amplification (SDA) is an isothermal nucleic acid amplification method. Primer contains a restriction site is annealed to template. Amplification primers are then annealed to 5' adjacent sequences (form a nick) and start amplification at a fixed temperature. Newly synthesized DNA are nicked by a restriction enzyme, polymerase starts amplification again, displacing the newly synthesized strands. 109 copies of DNA can be made in one reaction.This method is based on the ability of DNA polymerase to extend an oligodeox yribonucleotide primer, which is specifically hybridized to a single-stranded DNA template.