Objective To establish a simple and rapid new method for DNA extraction of FTA bloodstain samples.Methods Genomic DNA was extracted from FTA bloodstains of 1.2mm diameter by FTA-DNA direct extraction and FTA routine method respectively,and their genotypes were analyzed using ABI IdentifilerTM kit in 10?l and 25?l of reaction volume respectively.Results For 25?l of reaction volume,all DNA extracted by two different methods was successfully genotyped.For 10?l of reaction volume,however,the typing success rate of DNA extracted by FTA routine method was significantly lower than those by FTA-DNA direct extraction procedure.Using FTA routine method,the value of RFU ranged from 100 to 2000,and the peak imbalance result from preferential amplification of the smaller allele was a common phenomenon.Moreover,allelic dropout occurred in approximately nineteen percent of samples,and this was not obviously improved even if performed by automatic DNA workstation.However,using FTA-DNA direct extraction procedure,the typing results were similar to those in 25?l of reaction volume,and better results can be obtained using automatic DNA workstation.Conclusion The FTA-DNA direct extraction method is simple and rapid,and can be used to automatic establishment of DNA database with FTA bloodstains.

Objective To explore the effectiveness of whole genome amplification technology in DNA typing of trace samples.Methods Simulated trace samples which contain 1～20 cells were prepared by micromanipulation.Whole genome amplification was added before conventional PCR-STR typing step,to compare the effectiveness of PEP and MDA in DNA typing of trace samples from four aspects i.e.allele imbalance,allele drop-out,locus drop-out and pseudo allele (which contains the stutter peak).Results Amplification efficiency of MDA was higher than PEP method,but allele drop-out and pseudo allele were more frequently detected.Correct DNA typing rate of PEP is higher than MDA method,however,advantaged amplification of small fiagments DNA is more obvious.Conclusion MDA method is not suitable for the current STR typing.When the absolute amount of trace samples is quite small,we couldconsider using the PEP method to enhancethe sample quantity to meet the requirement of repeat testing.At the same time it could encounterthe failure of the large DNA fragments.