The Identification Of Five MiniSTR Loci Composite Amplification System

Background and objective：Short tandem repeat sequence (STR), which are widely exist ineukaryotic genomes tandem repeat sequence of DNA, also calledmicrosatellite DNA or simple repeated sequences. Its core sequence for2-6bp repeat units. They have many characteristics. Including Wide distribution,short clips, easy detection, genetic information,, much of Geneticinformation, the high of Genetic polymorphisms。AS is One of the mostimportant second generation of genetic markers,They have been widely usedin the forensic evidence domain, and they are the the most commonly usedand most effective means in individual identification. Especially，STRcomposite amplification kits(profilerPlus, Identifiler, powerPlexl6) and themultiple fluorescent detecting technology are widely used, make STRclassification technology are applied to a new level. At present，conventional STR composite amplification kits mainly includes13core sitesof CODIS (combined DNA index system) system and some autosomal STRsites,such as D2S1338, D19S433, PentaD,PentaE. the length of most of theSTR loci are more than200BP even to500BP. In the complex environment, especially in damp, high temperature, ultraviolet rays, exposure to the sun,bacteria, acid and other environmental factors will damage the DNA inbiological material, lead to rupture double chain and short the length of DNAmolecules. To this kind of degradative biological material,utilizeconventional STR classification technology，it is easy to lead to failure. It isseverely limits the use of STR classification technology in marginala anddegradative biological materials we can not get some important informationfrom these biological materials and go against these cases quickly detected.In order to make up for the defects of STR detection technology, in the basisof original STR technology, Bulter etc redesigned primers, maded thepositive and reversed primers for as possible to move to the core of repeatsequences, to reduce the length of the amplified pieces, while maintainingthe original STR sites genetic polymorphisms and STR typing. in2003,thetechnology was officially named miniSTR technology. Since then, manyscholars in different countries began to study miniSTR. in2006,ABcompany developed the first minifiler commodity kit, but it only includedeight miniSTR loci, Due to the small number loci,it had some defectst inindividual identification。Therefore, we screen five different miniSTR loci,to set up a new composite amplification system and kit. To improve the rateof effective STR typing in marginala and degradative biological materialsand reach the purposes of individual identification.Methods： On the bases of establishment of5Mini STR loci compositeamplification system and allelic ladder of Han people in Chongqing. weRefer to the guidelines worked by the United States DNA analysistechnology working group (TWGDAM), we research this multiplefluorescence composite amplification system for sensitivity, accuracy,genetic stability, species specificity, tissue specific, different extractionmethod to affect the results of classification, degradative model, corruptiveorganization and so on. To evaluate the applicative value of this multiplefluorescence composite amplification system in the forensic field.Results：In this composite amplification system, the sensitivity of template DNAis25pg. It has higher species specificity and tissue specificity. In thissystem,24cases were tested and analyzed, wo found that this system caneffectively used in individual identification and parentage testing. Comparedthe results of polyacrylamide gel electrophoresis，we found that both resultsare completely coincident. Compared the results of different extractionmethods for the same DNA samples, we found that the different extractionmethods had no effect on the results of DNA typing. Through to the researchof degradative model and the corruptive ganization, we found that thissystem for degradative material has good amplification effect, It Can be usedfor those degradative material that failure of DNA tying by routine STRcommodity kits. Conclusions：This multiplex system of5miniSTR loci that we builded has higheraccuracy of DNA typing、Genetic stability、sensitivity、species specificityand tissue specificity，It has no effect on the results of DNA typing fordifferent methods to extract DNA samples,For marginala and biologicalmaterial, our multiplex system of5miniSTR loci has higher successful ratethan routine STR commodity kits. It is suitable for individual identificationand paternity identification, Particularly for Marginala and degradativematerial. Our work will effectively promote the development of domesticminiSTR commodity kits.