Multiple displacement amplification
The Multiple Displacement Amplification (MDA ) and Isothermal multiple displacement amplification ( IMDA ) is a method of propagation of small amounts of DNA as starting material. Compared to the polymerase chain reaction, this method is particularly suitable for the growth of long DNA sequences (more than 2,000 to 100,000 base pairs). Another advantage is that it is the case of mixtures of DNA by this type of amplification without distortion (English bias) are, that is, that no individual DNA sequences are preferred or other mixtures at a disadvantage.
Because of these properties, this method is particularly suitable for the propagation of eg highly complex mixtures of genomic DNA. The starting material ( for example, the DNA of a few hundred cells) rich few nanograms, which is propagated about 1000 to 10,000 units by the MDA.
The MDA is carried out in comparison with the polymerase chain reaction at a constant temperature. First, the double stranded template DNA is separated by denaturation into single strands. Subsequently, the Phi29 DNA polymerase and a mixture of deoxynucleotides is added. The phi29 DNA polymerase binds to the single strands of DNA, and then establishes the second complementary strand. The complementary strand is per second from about 25 to 50 bases with an error rate of 1 error to 3 x 106, this increases bases. In comparison, a conventional PCR with Taq polymerase is expected at a rate from 1000 to 2000 bases per minute and an error rate of 1 error on 2 × 103 bases.