Data for Y-chromosome haplotypes defined by 17 STRs (AmpFLSTR Yfiler) in two Tunisian Berber communities

The 17 Y-chromosomal short tandem repeats (STRs) included in the AmpFLSTR Yfiler PCR Amplification Kit (AB Applied Biosystems) (DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS385, DYS437, DYS438, DYS439, DYS448, DYS456, DYS458, DYS635 and GATA H4) were typed in two Berber communities, a small village (Takrouna) and a town (Sejenane), from North Tunisia. As expected, diversity was higher in the town, even when compared with a pool of three small Berber communities, probably due to the combination of different founder effects and genetic drifts operating in the small villages.     

Results of the GEP-ISFG collaborative study on two Y-STRs tetraplexes: GEPY I (DYS461, GATA C4, DYS437 and DYS438) and GEPY II (DYS460, GATA A10, GATA H4 and DYS439)

A collaborative exercise was carried out by the Spanish and Portuguese ISFG Working Group (GEP-ISFG) in order to evaluate the performance of two Y-chromosome STR PCR tetraplexes, which include the loci DYS461, GATA C4, DYS437 and DYS438 (GEPY I), and DYS460, GATA A10, GATA H4 and DYS439 (GEPY II). The participating laboratories were asked to type three samples for the eight markers, using a specific amplification protocol. In addition, two control samples, with known haplotypes, were provided. The results obtained by the 13 different participating laboratories were identical, except for two laboratories that failed to type correctly the same two samples for GATA C4. By sequence analyses, two different GATA C4 allele structures were found. One control sample (allele 21) and two questioned samples (allele 22, correctly typed by all the laboratories, and allele 25) presented the following repeat structure: (TCTA)4(TGTA)2(TCTA)2(TGTA)2(TCTA)n, but different from the one found for allele 26 in one sample included in this exercise, as well as in the second control sample (allele 23), namely (TCTA)4(TGTA)2(TCTA)2(TGTA)2(TCTA)2(TGTA)2(TCTA)n. The collaborative exercise results proved that both Y-tetraplexes produce good amplification results, with the advantage of being efficiently typed using different separation and detection methodologies. However, since GATA C4 repeat presents a complex structure, with alleles differing in sequence structure, efficient denaturing conditions should be followed in order to avoid typing errors due to sizing problems.     

Population data for six X-chromosome STR loci in a Rio de Janeiro (Brazil) sample: Usefulness in forensic casework

This study presents data for the X-chromosome STR loci DXS7133, DXS7424, DXS8378, DXS6807, DXS7423 and DXS8377. In order to establish a database, unrelated individuals (males and females) from Rio de Janeiro were typed for the above loci. No significant differences were observed between allele frequencies in male and female samples (non-differentiation exact P values ≥ 0.156). Hardy-Weinberg equilibrium was tested in the female sample and no significant deviations were found. All six markers have shown to be highly polymorphic in our sample with gene diversities varying between 0.6797 for DXS7133, and 0.9260 for DXS8377. Pairwise linkage disequilibrium analysis did not allow discharging a possible association between DXS7133 and DXS7424 alleles in Rio de Janeiro population. Parameters of forensic interest, like PD_M, PD_F, Het_obs, Het_exp, were calculated for each locus. The high discrimination power estimated in both males and females, as well as mean exclusion chance in father/daughter duos and in father/mother/daughter trios, demonstrates the usefulness of these six markers in forensic investigation.     

Y-chromosomal STR haplotypes in a Gypsy population from Portugal

We analyzed 17 Y-chromosomal STR loci in a population sample of 126 unrelated Portuguese Gypsies. Fifty three different haplotypes were found, three represented with considerable high frequencies (≥8.7%). The percentage of unique haplotypes (71.2%) was rather low as well as haplotype diversity (94.37%). In the comparison with available Portuguese population data and with those from other Gypsy and general population samples from Bulgaria, Lithuania and Spain, our sample showed significant differences in comparison with the general population data from Portugal, Spain and Bulgaria. Significant differences were observed with Bulgarian Gypsies, but not with the Spanish or Lithuanian groups. The Gypsy populations from Portugal, Spain and Bulgaria were found to be more closely related to each other than with the general population from their own countries.     

Mismatch distribution analysis of Y-STR haplotypes as a tool for the evaluation of identity-by-state proportions and significance of matches--the European picture

We suggest the use of the mismatch distribution methodology as an easy way to estimate the distance between all pairs of haplotypes present in a sample. This approach allows the evaluation of the proportion of pairs of Y-STR haplotypes that are prone to become identical by state (IBS), in one generation, by recurrent mutation, a statistic of major importance in the forensic field. The mismatch approach presents some advantages alternatively to the empirical one, since it is not necessary to have simultaneous information on STRs and SNPs, and it allows the evaluation of IBS also within-haplogroups. The estimation of IBS at an European scale showed that there is a high population substructuring for this parameter, increasing from southern-central European countries towards west and north, in accordance to what was found for Y-biallelic markers. This result seems to imply a more careful use of large databases for matching evaluation, even in the absence of population structure for general Y-STR diversity. Furthermore, mismatch distribution can be used to measure the distance between a particular haplotype and all the haplotypes in a sample. When applied to the most frequent haplotypes in Europe it revealed that the opportunity for IBS is not directly related to the frequency of a haplotype, but highly dependent on the proportion of neighbouring haplotypes--so, that reporting on the haplotype frequency for evaluating the significance of a match can be misleading.     

Pros and cons in the use of SNPs in forensic kinship investigation: a comparative analysis with STRs

Recent advances in single nucleotide polymorphisms (SNPs) research have raised the possibility that these markers could replace the forensically established short tandem repeats (STRs). In this work, we compare STRs and SNPs applicability for kinship investigation in terms of expected informative content and probability of occurrence of "difficult cases" (when isolated Mendelian incompatibilities between alleged father and child are found). Since SNPs have a much lower mutation rate than STRs, these difficulties were expected to occur less frequently if SNPs were used instead of STRs. The purpose of this paper is to make some simulations allowing the estimation of how often such difficult cases are expected to occur using both types of markers and how serious can be their impact in routine work. Our results demonstrate that a battery based exclusively on SNPs matching the informative power of current STR kits would be prone, if applied to routine paternity investigation, to the occurrence of cases where the statistical evidence would be inconclusive. We infer that the introduction of a SNP based strategy, as a substitute to the now classical STR approach poses statistical problems that must be carefully evaluated.     

STR allelic frequencies for an African population sample (Equatorial Guinea) using AmpFlSTR Identifiler and Powerplex 16 kits

We present allele frequencies and forensic parameters for 17 STRs included in the AmpFlSTR Identifiler (CSF1PO, D2S1338, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D19S433, D21S11, FGA, TH01, TPO and VWA) and Powerplex 16 System (CSF1PO, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D21S11, FGA, Penta D, Penta E, TH01, TPO and VWA) in a sample of 134 unrelated individuals from Equatorial Guinea located in Western Africa, between Cameroon and Gabon. Hardy-Weinberg equilibrium was tested for each locus and the sample was compared with five African databases: Promega's and AB Applied Biosystems African-Americans and samples from Mozambique, from Cabinda (Angola) and Guinea-Bissau.     

Population data on 15 autosomal STRs in a sample from East Timor

Allele frequencies for the fifteen STRs included in the AmpF/STR Identifiler (CSF1PO, D2S1338, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D19S433, D21S11, FGA, TH01, TPO and VWA) were estimated from a sample of 186 unrelated individuals from East Timor. No deviations from Hardy-Weinberg equilibrium were observed (only after applying the Bonferroni correction in the cases of D2S1338, TPO and D5S818). Genetic parameters of forensic interest were calculated and comparison with geographically nearby populations was performed.     

STR data for the AmpFlSTR profiler plus loci from Macau (China).

Allele frequencies for the nine STRs included in the AmpFlSTR profiler plus kit (D3S1358, VWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317 and D7S820) were estimated from a sample of 87 unrelated individuals living in the region of Macau, a territory located in the southeastern coast of China.     

STR data (CD4, CSF1PO, F13A01, FES/FPS, MBPB, TH01, TPOX) from North Portugal.

Allele frequencies for seven STRs (CD4, CSF1PO, F13A01, FES/FPS, MBPB, TH01, TPOX) were estimated from samples (sized between 300 and 940) of unrelated individuals born in North Portugal.