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.