Effect of phi29 polymerase-based multiple strand displacement whole genome amplification on the proportion in DNA mixtures

Multiple displacement amplification (MDA), an isothermal whole genome amplification method, has been applied extensively for its long amplification products and low bias. Because of preferential amplification and allelic drop-out with MDA when dealing with low template DNA (< 100 pg), it hasn't been used in forensic science. On the other hand, the MDA was reported that it could enlarge the proportion of minor contributor's alleles in a mixture. To evaluate the application of MDA in DNA mixture issues, we used a new commercial MDA kit, made different mixture ratios from 1:5 to 1:40, and then compared the mixture proportion and locus dropout rate of minor contributor DNA between PCR-STR with MDA and PCR-STR without MDA. Meanwhile, we evaluated the reproducibility of PCR-STR with MDA in different ratios. The results showed improvements of locus drop-out rate in PCR-STR with MDA. Reproducible and complete minor contributor's alleles in different mixture ratios showed a fine reproducibility of MDA method. These results suggest that MDA might be an auxiliary method for dealing with forensic mixture issues.