The new guidelines for paternity analysis in Germany—how many STR loci are necessary when investigating duo cases?

The requirements in the new German guidelines for paternity analysis have not only changed according to the so-called Gendiagnostikgesetz, the new German law regulating human genetic as well as paternity analyses, but also regarding the minimal number of short tandem repeats (STRs) which should be investigated (15 STRs) and the minimal required average exclusion chance (99.999 %). Even in paternity analyses involving only two people (e.g., father and child or mother and child), this exclusion chance is mandatory. A retrospective analysis of 330 father–child cases from our routine investigations showed in 142 cases (43 %) an individual exclusion chance below 99.999 % when using 15 STRs as required, in our routine work provided by the Powerplex® 16 kit which is reported to have an average exclusion chance of 99.988 %. Therefore, these same 330 father–child pairs were additionally analysed using the Powerplex® 21 kit and 120 of these duos were additionally analysed using the Powerplex® ESX17 kit enabling the analysis of 20 or 16 loci respectively. Now, an individual exclusion chance of more than 99.999 % could be achieved in 95.5 % (Powerplex® 21; calculation without the results of D6S1043), 98.8 % (Powerplex® 21; calculation with the results of D6S1043, using allele frequencies established in this study for a German and a West African population) and 98.3 % (Powerplex® ESX17). These data clearly demonstrate that in duo cases, more than the required 15 STR loci have to be investigated to obtain sufficient results.     

Evaluation of forensic genetic efficiency parameters of 22 autosomal STR markers (PowerPlex® Fusion system) in a population sample of Arab descent from Jordan

Jordan is a country located in the Middle East, on the East Bank of the Jordan River. In this study, the PowerPlex® Fusion (PPF) system was used to determine the allele frequencies and forensic efficiency parameters of 22 autosomal STR loci. Autosomal STR information was collected from the blood samples of 500 individuals belonging to the Jordanian population of Arab descent. The PPF system (Promega Corporation) was used to amplify the 22 autosomal STRs and the amplified samples were analysed on the 3130xl Genetic Analyser using GeneMapper ID-X 1.2 software (Applied Biosystems). All the autosomal STR loci met the requirements of the Hardy-Weinberg equilibrium after Bonferroni correction. This study revealed that the most informative locus among the 22 STR loci (excluding Amelogenin and DYS39) was Penta E locus (power of discrimination (PD) = 0.99), while the least informative locus was TPOX locus (PD = 0.834). The combined matching probability (MP) of the 22 loci was 1.9 × 10^?28. These forensic genetic parameters indicated the practicality of analysing these 22 STRs in forensic DNA identification and paternity testing among individuals from the Jordanian Arab population.     

Parentage testing with 14 STR loci and population data for 5 STRs in the Slovenian population

In order to apply a set of 14 short tandem repeat (STR) loci in parentage testing, we performed a population genetic study on a sample of 260 unrelated people from the Slovenian population. Genotypes for the 14 STRs were determined using three multiplex polymerase chain reactions (PCR) and automated fluorescent detection. The allele frequencies of the STR loci D5S818, D13S317, D7S820, D8S1179 and D18S51 showed no deviation from the Hardy-Weinberg equilibrium and agreed well with other Caucasian populations. We resolved a series of 181 parentage disputes of which 29 were exclusions. In all cases, evidence for exclusion was obtained by at least 4 informative STRs out of the 14 loci analysed. The 14 loci combined comprise a highly discriminating test suitable for paternity and identity testing in the Slovenian population, with an average estimated mutation rate of 1.2x10(-3), a combined calculated power of exclusion of 99.99974% and paternity index (PI) value of >10(6) in 72% of the inclusion cases and >10(5) in 91% of the inclusion cases.     

Fourteen non-CODIS autosomal short tandem repeat loci multiplex data from Taiwanese

Interest in the development of polymorphic short tandem repeat (STR) markers unlinked to the CODIS loci is growing among forensic practitioners. We developed a multiplex system in which14 autosomal STR (D3S1744, D4S2366, D8S1110, D12S1090, D13S765, D14S608, Penta E, D17S1294, D18S536, D18S1270, D20S470, D21S1437, Penta D, and D22S683) could be amplified in one single polymerase chain reaction. DNA samples from 572 unrelated Taiwanese Han subjects were analyzed using this 14 STR multiplex system. Thirty parent–child pairs of parentage testing cases with a combined paternity index (CPI) below 1,000 and 32 parent–child pairs with single-step mutations found in AmpFℓSTR Identifiler loci were also recruited for validation of the newly developed system. DNA sequencing was performed for novel STRs and novel alleles found in these subjects. The distributions of allelic frequencies for these autosomal STRs and sequence data, allele nomenclature for the STRs, and forensic parameters are presented. The discrimination power in our multiplex loci ranged from 0.6858 (D18S536) to 0.9168 (Penta E), with a combined discrimination power of 0.999999999. It provides additional power to distinguish the possible single-step mutations in parent–child pairs and improves the ability to prove parentage by increasing the CPI. The combined power of exclusion of these 14 loci in Taiwanese Han in this study was 0.9999995913. In conclusion, this 14-autosomal STRs multiplex system provides highly informative STR data and appears useful in forensic casework and parentage testing.     

Evaluation of the paternity probability on an application of minisatellite variant repeat mapping using polymerase chain reaction (MVR-PCR) to paternity testing

Minisatellite variant repeat (MVR) mapping using polymerase chain reaction (PCR) was applied to a practical case of paternity testing to evaluate the paternity probability. In order to obtain single allele mapping by allele-specific MVR-PCR, three flanking polymorphic sites for each of the MS31A and MS32 loci were investigated and all three individuals were typed as heterozygous for at least one flanking polymorphic site at each locus. Allele-specific MVR-PCR was then performed using genomic DNA. It was confirmed that one allele in the child was identical to that from the mother and the other one in the child was identical to that from the alleged father. Mapped allele codes were also compared with those in the database by dot-matrix analysis, and no identical allele was found although some motifs were shared with Japanese alleles. The paternity index and the probability of paternity exclusion in the case at these two MVR loci were calculated using the presumed values of the allele frequencies. These studies seem to illustrate the practical value of MVR mapping of MS31A and MS32 loci in paternity testing.     

The effect of FBI CODIS Core STR Loci expansion on familial DNA database searching

1000 profiles chosen randomly from an in-house database of 6000 profiles were searched against the database for matches with at least one shared allele per locus. The database contains profiles that have been analyzed with Identifiler Plus (15 markers) for biological relationship and DNA identification purposes and both true and false matches are expected to be obtained. 100 pairs of at least one true paternity match and one false match were selected and were initially supplemented with 5 additional STRs representing the new Core CODIS set. Study of the LR value showed that when false matches were treated as paternity matches, the expansion of the marker set severely diminished the LR values obtained compared to true matches and the false positive ratio of familial database searching. When false matches were treated as full-sibling matches, the expansion to 20 STRs also diminished the number of false matches and the corresponding LR values compared to true full-sibling cases, but the effect was less dramatic. Addition of the SE33 marker, further promoted distinction between true and false matches both in paternity and full-sibling cases. Counting the number of shared alleles presented improved distinction efficiency between true and false matches after STR expansion to20 and 21 STRs but remains a less valuable method of familial DNA database searching compared to LR.     

Autosomal STR allele frequencies for the CODIS system from a large random population sample in Chile

The thirteen autosomal STR loci of the CODIS system were typed from DNA of 732 unrelated male individuals sampled from different locations in Chile. This is the first report of allele frequencies for the thirteen STRs loci defined in the CODIS system from the Chilean population.     

High autosomal STR allele sharing between full siblings

Multiplexes of polymorphic tetranucleotide Short Tandem Repeats (STRs) are regularly employed for forensic identification and kinship testing. If the DNA profiles of two samples match, there is a high probability that the samples have originated from the same individual. Match probabilities are calculated to evaluate the strength of DNA evidence. Relatives often share more alleles than unrelated individuals. High allele sharing among relatives can complicate source attribution of a DNA profile. In this paper, a case of high allele sharing of autosomal STR loci between two full siblings is reported and implications in source attribution are discussed.     

Assessing paternities with inconclusive STR results: The suitability of bi-allelic markers

In paternity testing the genetic profiles of the individuals are used to compare the relative likelihoods of the alleged father and the child being related as father/offspring against, usually, being unrelated.In the great majority of the cases, analyses with the widely used sets of short tandem repeat markers (STRs) provide powerful statistical evidence favouring one of the alternative hypotheses. Nevertheless, there are situations where the final statistical result is ambiguous, mostly because the alleged father shows incompatible genotypes at a few loci along with a very high paternity index in the remaining systems. In these cases, the possibility that the alleged father is actually a close relative of the real one (son, father or brother) can reasonably be raised.In such cases, when the statistical evidence obtained is considered as insufficient, the common practice is to extend the set of analysed markers. In this context, many authors have suggested that bi-allelic markers, such as single nucleotide (SNP) or insertion/deletion (Indel) polymorphisms, are markers of choice, as they are incomparably less prone to mutation than STRs.In this work we address the soundness of this claim and the consequences of this strategy, analyzing the a priori odds both for (a) expected number of Mendelian incompatibilities, and (b) expected values for the final likelihood ratios. Moreover, one hundred real pairs of second degree relatives, typed for two sets of markers: 15 STRs plus 38 Indels, were used to simulate paternity testing. Our data show that, for the number of markers commonly considered, the results from an extended battery of SNPs or Indels should be interpreted with caution when relatives are possibly involved.     

The new Powerplex? ESX17 and ESI17 kits in paternity and maternity analyses involving people from Africa—including allele frequencies for three African populations

Paternity and maternity investigations in immigration procedures are frequently done in Germany. Since mostly only one parent and one or more children are investigated, the occurrence of possible mutational events has to be interpreted with great care and the analysis of as many STRs as possible is recommended. The new Powerplex? ESX17 and Powerplex? ESI17 kits from Promega comprising both eleven established STRs and additionally the loci D1S1656, D2S441, D10S1248, D12S391, and D22S1045 (in different order) are potential tools in such paternity or maternity analyses, but only few allele frequency data for the five new loci exist. Here, we provide allele frequencies for the five additional STRs from three different populations from Africa. In addition, we present two maternity cases and one paternity case in which a clear inclusion or exclusion of the alleged parent could only be achieved by the additional application of the new Powerplex? ESX17 kit.     

STR sequence analysis for characterizing normal, variant, and null alleles

DNA sequence variation is known to exist in and around the repeat region of short tandem repeat (STR) loci used in human identity testing. While the vast majority of STR alleles measured in forensic DNA laboratories worldwide type as "normal" alleles compared with STR kit allelic ladders, a number of variant alleles have been reported. In addition, a sequence difference at a polymerase chain reaction (PCR) primer binding site in the DNA template can cause allele drop-out (i.e., a "null" or "silent" allele) with one set of primers and not with another. Our group at the National Institute of Standards and Technology (NIST) has been sequencing variant and null alleles supplied by forensic labs and cataloging this information on the NIST STRBase website for the past decade. The PCR primer sequences and strategy used for our STR allele sequencing work involving 23 autosomal STRs and 17 Y-chromosome STRs are described along with the results from 111 variant and 17 null alleles.     

Expanding beyond the current core STR loci: An exploration of 73 STR markers with increased diversity for enhanced DNA mixture deconvolution

Current approaches to mixture deconvolution of complex biological samples at times do not have the capability to resolve component contributors in DNA evidence. Additional short tandem repeat (STR) loci were sought that may improve the forensic genetic analysis of mixtures. This study presents exploratory data of a multiplex comprised of 73 highly polymorphic STRs (referred herein as the 73Plex) that were selected because of their high diversity due to sequence variation. These STRs (or a subset of them) may be considered as candidates that may augment current core markers capabilities for DNA mixture deconvolution. Population genetics analyses were performed for each locus using DNA samples from 451 individuals comprising three U.S. populations. Sequence-based heterozygosities ranged from 72% to 98%, where only two loci (D10A97 and D6A7) fell below 80%. Mixture deconvolution capabilities for two-person mixtures were assessed based on complete allele resolution per locus (i.e., four alleles observed) of pairwise mixtures using in silico methods. A subset of 20 highly informative loci (referred herein as the 20Plex) from the 73Plex was compared to the 20 CODIS core loci on all population samples with full DNA profiles for both panels (i.e., no locus dropout; n = 443). Based on proportion of loci displaying four alleles, the 20Plex outperformed the CODIS core loci with increases of 82.6% and 89.3% using length-based and sequence-based alleles, respectively. A combination of 17 STR from the 20Plex and 3 CODIS loci gave the highest capacity for resolving allelic components per locus. These data illustrate the increased value of utilizing sequenced-based alleles of additional STR loci. Furthermore, there are a number of candidate STR loci that could notably augment the current core STR loci and enhance mixture interpretation capabilities.     

Mutation rate evaluation at 21 autosomal STR loci: Paternity testing experience

The short tandem repeats (STRs) or microsatellites are used for paternity testing and these sequences mutate more rapidly than bulk DNA sequences. A total of 746 paternity cases were analysed to understand the mutation rate of 21 autosomal STR loci. We identified 41 mutations in 11 STR Loci with a maximum at SE33. No mutations occurred in the remaining 10 STR loci. The overall average mutation rate was estimated as 0.004523 and the estimated locus-specific mutation rate varied between 0.001214 and 0.016990. Among these 90.24% was accounted for single-step mutation, 2.44% for two steps, and 7.32 % for three or muti steps. The obtained data is crucial and could be helpful for ensuring the accuracy of DNA testing and interpretation.     

The recombination landscape around forensic STRs: Accurate measurement of genetic distances between syntenic STR pairs using HapMap high density SNP data

Family studies can be used to measure the genetic distance between same-chromosome (syntenic) STRs in order to detect physical linkage or linkage disequilibrium. However, family studies are expensive and time consuming, in many cases uninformative, and lack a reliable means to infer the phase of the diplotypes obtained. HapMap provides a more comprehensive and fine-scale estimation of recombination rates using high density multi-point SNP data (average inter-SNP distance: 900 nucleotides). Data at this fine scale detects sub-kilobase genetic distances across the whole recombining human genome. We have used the most recent HapMap SNP data release 22 to measure and compare genetic distances, and by inference fine-scale recombination rates, between 29 syntenic STR pairs identified from 39 validated STRs currently available for forensic use. The 39 STRs comprise 23 core loci: SE33, Penta D &; E, 13 CODIS and 7 non-CODIS European Standard Set STRs, plus supplementary STRs in the recently released Promega CS-7? and Qiagen Investigator HDplex? kits. Also included were D9S1120, a marker we developed for forensic use unique to chromosome 9, and the novel D6S1043 component STR of SinoFiler? (Applied Biosystems). The data collated provides reliable estimates of recombination rates between each STR pair, that can then be placed into haplotype frequency calculators for short pedigrees with multiple meiotic inputs and which just requires the addition of allele frequencies. This allows all current STR sets or their combinations to be used in supplemented paternity analyses without the need for further adjustment for physical linkage. The detailed analysis of recombination rates made for autosomal forensic STRs was extended to the more than 50 X chromosome STRs established or in development for complex kinship analyses.     

Mutation rate estimates for 13 STR loci in a large population from Rio Grande do Sul, Southern Brazil

Short tandem repeat (STR) polymorphisms have been extensively used in forensic genetics analysis. Knowledge about the locus-specific mutation rates of STRs improves forensic probability calculations and interpretations of diversity data. To incorporate single-locus diversity information into autosomal STR mutation rate estimations, 13 STR loci were studied during 2007–2009 in 10,959 paternity investigation cases from Rio Grande do Sul, the southernmost state of Brazil, covering an overall number of 284,934 allelic transfers. A total of 355 mutations were identified; 348 repeats were gains or losses of one step, three were gains or losses of two steps, and four were gains or losses of not stepwise mutation. The mutation rates ranged from 4.6?×?10^?5 to 2.3?×?10^?3, and the overall mutation rate estimate was 1.2?×?10^?3. The average of the paternal mutation rate (1.8?×?10^?3) was five times higher than the maternal rate (0.36?×?10^?3). The observed mutational features for STRs have important consequences for forensic applications, including the definition of criteria for exclusion in paternity testing and the interpretation of DNA profiles in identification analysis.     

Allele frequencies of nine STR loci of Jewish and Arab populations in Israel

DNA typing of nine short tandem repeat (STR) loci was carried out on unrelated Israeli Jewish and Arab individuals. All loci were highly polymorphic and the distribution of the obtained genotypes did not deviate from Hardy-Weinberg equilibrium. A comparison between Jewish and Arab population data revealed statistically significant differences in allele frequency distributions for some of the loci. The results presented in this study enable the use of these nine STR loci for forensic, identification and paternity cases in the Jewish and the Arab populations of Israel. Received: 9 April 2001 / Accepted: 2 July 2001     

Can brothers share the same STR profile?

This report demonstrates the limits of DNA identification when siblings are involved.The Israeli DNA database routinely amplifies suspects samples using the PowerPlex^® ESI16 system (Promega). While uploading a series of suspects into the database software, we found an unusual high number of shared alleles between two suspects 31 out of 32 alleles. Verification of their demographic data identified them as brothers. After confirmation of their paternity affiliation using the AmpFlSTR^®YFiler™ (Applied Biosystems), we used two other multiplexes kits to improve the differentiation rate. The PowerPlex^® ESX17 System (Promega) added one locus, SE33, who exhibits four different alleles. The second kit, the AmpFlSTR^®MiniFiler™ (Applied Biosystems) added three more loci. Only one allele difference was found.In order to increase the discrimination power between related and unrelated individuals, we recommend that the DNA laboratories consider using a larger multiplex typing kit in cases like the one informed here.     

Simultaneous typing of the STR loci,vWF and HumTPO,using discontinuous polyacrylamide gel electrophoresis

Analyses of short tandem repeat (STR) loci are very useful for improving the accuracy of paternity determination. Combined use of several STRs makes this test even more accurate. We have devised a simple but effective method which consists of the co-amplification of two STR loci (vWF and HumTPO) in a single test tube, separation of the PCR products using discontinuous polyacrylamide gel electrophoresis, and detection using sensitive silver staining. An appropriate combination of PCR primer pairs gave a high resolution and good separation of the two STR bands in the same lane on the same gel. Many combinations of STR loci have potential usefulness in paternity and individualization testing or population genetic studies in forensic practice.     

A proposed nomenclature for 15 canine-specific polymorphic STR loci for forensic purposes

We performed a population study on 15 polymorphic STR loci (FH2010, FH2079, PEZ2, VWF.X, FH2054, FH2087Ub, FH2611, WILMS-TF, PEZ12, PEZ15, PEZ6, FH2087Ua, ZUBECA4, ZUBECA6, FH2132) on 131 randomly selected dogs. Alleles were identified and grouped according to their estimated fragment length using fixed allelic bins encompassing one base-pair. The allele assignment was confirmed by sequence analysis of homozygote and cloned heterozygote alleles. In order to develop a uniform repeat-based nomenclature, extensive sequence analysis was performed on a selection of alleles from each STR locus. The proposed nomenclature refers to the internationally recognised recommendations for human-specific STR loci in forensic applications. The 15 canine-specific STR loci were grouped into 3 classes (simple STRs, compound STRs and complex/hypervariable STRs) according to their complexity and variability within the repeat structure. Finally, we evaluated the precision of fragment size estimation on a capillary electrophoresis platform and demonstrated reproducibility of fragment length estimation for single base-pair intermediate alleles.     

Population data of 19 autosomal STR loci in the Li population from Hainan Province in southernmost China

In the present study, population data of 19 autosomal STR loci included in the Goldeneye™ DNA ID System 20A in 653 Li individuals was obtained and population genetic relationships among 13 populations were investigated. MDS and phylogenetic analysis suggested that the Hainan Li population kept a close genetic relationship with the Chinese Han populations, especially for Southern Han populations (Guangdong Han, Sichuan Han, and Hunan Han). Our results indicated that the 19 autosomal STRs are highly discriminative and polymorphic in the Hainan Li population suitable for personal forensic identification and paternity testing.