ABSTRACT
Objective To explore the mutation types and disciplines of STR commonly used in forensic in gynecologic and breast cancerand investigate the application of microdissection in forensic practice involving tumor tissue. Methods DNA of tumor tissues, adjacent normal tissues and peripheral blood from 62 patients with breast cancer, 62 patients with gynecologic cancer and 10 patients with benign gynecologic tumor were amplified by PowerPlex 21 System kit and Argus X-12 kit. Capillary electrophoresis of PCR products was carried out on an ABI 3130 Genetic Analyzer to obtain genotypes. Some tumor tissues with STR variation were microdissected. Results The genotype of peripheral blood in cancer patient was consistent with that of corresponding normal tissue. 4 types of STR variations were found in 46.77% gynecologic cancer tissues, compared with that in benign tumor tissues and breast cancer, the difference of STR variation was significant(P<0.01,P=0.009). The genotype of stromal cells separated by microdissection was consistent with that of corresponding adjacent normal tissue. Conclusion The STR loci detected in the study with poor stability are not suitable for forensic cases involving gynecologic cancer tissues. The genotype of stromal cells separated accurately from tumor tissues by microdissection could represent the normal DNA genotype of the individual with cancer. Microdissection is an effective solution in forensic cases with tumor tissues.
ABSTRACT
Objective The purpose of this study was to detect the degradation degree of long-term formalin fixed tissue and to compare the detection rate of STR with SNP. Methods DNA was extracted from 24 formalin-fixed tissues stored at -20 ℃ for five years, and the concentration and degradation index of DNA was quantified with Quantifiler? Trio DNA Kit. A 55-SNP multiplex SNaPshot assay and PowerPlex? 21 system were used to amplify SNP and STR loci, respectively. Results The results showed that the degradation indexes of 24 specimens were ranged from 1~8. The SNP genotypes of the 24 specimens were completely consistent with the non-degraded DNA from the same individuals and the successful genotyping rate was 100%. However, 33 allele dropouts were observed with STR genotyping in 8 samples, of which the degradation index was higher than 2.6, and the fragment size of the 75.8% allele was longer than 300bp. The likelihood ratio based on 16 typable STR loci in the sample was close to that onthe basis of 54 SNPs. However, likelihood ratio based on more than 17 STR loci was over that accord to 54 SNPs. There was a negative correlation between the fragment size of STR and the allele detection rate, and a negative correlation also observed between the degradation index of samples and the allele detection rate except for two samples with mild degradation. Conclusion This study validated that the long-term formalin-fixed tissues were susceptible to degradation, and the SNP was more suitable for detecting these tissues than STR typing system. However more SNP loci are needed to test in order to increase the discrimination power.
ABSTRACT
<p><b>OBJECTIVE</b>To investigate genetic polymorphisms of 12 X chromosome short tandem repeat (X-STR) loci in ethnic Hebei Han population using an Investigator Argus X-12 amplification kit.</p><p><b>METHODS</b>DNA was extracted for 198 unrelated individuals (96 males and 102 females) and amplified with a fluorescence labeled multiplex PCR system. PCR products were separated and genotyped with capillary array electrophoresis.</p><p><b>RESULTS</b>Only DXS10103 and DXS10101 showed significant linkage disequilibrium at the 12 X-STR loci. One hundred and forty-eight alleles, including 22 off-ladder (OL) alleles, were observed at the 12 X-STR loci in the population. The heterozygosity and polymorphic information content (PIC) were 0.5074-0.9143 and 0.4377-0.9079, respectively. The power of discrimination (PD) was 0.5074-0.9143 in males and 0.6876-0.9863 in females. The mean exclusion chance was 0.4377-0.9079 in the trios cases and 0.2984-0.8373 in the duo cases, respectively.</p><p><b>CONCLUSION</b>The Investigator Argus X12 amplification system is highly polymorphic in ethnic Han population from Hebei and is useful for personal identification and paternity testing.</p>