Objective: To produce standard allelic ladders for four STR loci(D7S817, D10S1432, D10S1213 and D18S865) by recombined plasmids and use them in the research of genetic polymorphism.
Methods: After being amplified by PCR, different STR allelic fragments were isolated from the polyacryramide gel. The STR allelic fragments were eluted into distilled water and reamplified by PCR to obtain purified allelic fragments. Next, the purified allelic fragments were subcloned individually into the PUC plasmid vectors, and the size and structure of the inserts were confirmed by the analysis of their DNA sequences. Then we transfected the PUC plasmid vectors into E. coli DH5 alpha cells, worked on selective culture, and finally, mixed the alleles of the four STR loci respectively.
Results: The standard allelic ladders for four new loci (D7S817, D10S1432, D10S1213 and D18S865) were obtained, with which the genetic polymorphisms of four new loci in Chinese Hans and Dongxiang ethnic groups were studied.
Conclusion: The standard STR allelic ladders acquired by this method are of high value in forensic practice, and they are applicable to the analysis of genetic polymorphism.