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Objective To analyze and discuss four methods of calculating likelihood ratio of DNA mixture. Methods In the case with CNAS-T0757 proficiency testing in 2013, the likelihood ratios were calculated and compared among four methods, including unrestricted combinatorial method, Clayton’s method, p2 principle method, and recommendations fromISFG . Results The likelihood ratios were maximumby Clayton’s method and recommendations fromISFG , followed by result of the unrestricted combinational method. The minimu mlikelihood ratio was obtained by p2 principle. Conclusion The unrestricted combi-national method could give furthest consideration to both information preservation and appraiser protection.
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Objective Establish and evaluate the method of number of alleles identical by state in full sib test.Methods Sib pair group and unrelated individual pair group were genotyped in 13 STR loci,statistical calculation was carried out.Results Through analysis by discriminant function the posterior probability of membership in each group and error of the posterior probability was obtained.The discriminant function in sib group is L sib =-27.087 03+3.202 32S(S:number of alleles identical by state);The discriminant function in unrelated individual group is:L unrelated =-7.495 63+1.685 09S.The average error of the posterior probability in sib and unrelated pair group is 0.026 5.Conclusion When the number of alleles identical by state is more than 17 or less than 8,posterior probability of a full sib or unrelated individuals is more than 0.998 0 or 0.999 4,respectively.The method based on the number of alleles identical by state in full sib test is credible in identifying sib pair relationship.
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Objective To investigate the influence of case environment, extracting position and method on STR typing of nail DNA. Method Decayed body nails were selected from cases. Nails nuclear DNA were extracted from different positions, digestion system and time. After phenol/chloroform extracting and PCR reaction, the STR typing had been studied. Results Nail samples from middle and root positions offer satisfactory results. Conclusion The nail is a useful sample for forensic cases.
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Objective To study the DNA extraction and its typing in cigarette butts. Method Chelex 100 extraction method was used to extract DNA of 170 cigarette butts, STR loci were typed after PCR amplification by Profiler Plus kit. Results 21 cigarette butts from one volunteer have no results, the others were all obtained typing results. The samples which were added a little tobacco have no results. Sometimes DNA in sponge contacted with mouth was typed. The small fragment loci were typed in cigarette butts which had been reserved for six months. Conclusion Cigarette butt can be typed by DNA analysis, which is useful in forensic identification.
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Rhesus monkey (Macaca mulatta)ABO blood typing was carried out by agglutination test with anti human sera, and monoclonal antibodies against A and B blood group antigcus Blood Samples of 113 monkeys were tested. The results showed that there wete no human like A and B agglutinins and anti-A and anti-B agglutnins on the surface of the red blood cells and in the sera of monkeys. How ever human like blood group substances were found in monkey's galiva lemonsliated by agglutination inhibition test. The ABO phenotype frequoncies of Rhesus monkey were as follows: A-17. 70 %;B-52,21 %;AW-20, 36% and O-9. 73 % which of ther from foreign reports.