Mutational analysis of 23 autosomal short tandem repeats based on trio paternity testing in the Korean population

This study aimed to estimate A-STR mutation rates in 2,317 Korean parent-child trios by examining 20 Combined DNA Index System (CODIS) core loci (D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D21S11, CSF1PO, FGA, TH01, TPOX, vWA, D1S1656, D2S441, D2S1338, D10S1248, D12S391, D19S433, and D22S1045) and three non-CODIS loci (Penta E, Penta D, and SE33). Locus-specific mutation rate estimates varied from 0.00 to 8.63 × 10-3 per generation, with an average mutation rate of 1.62 × 10-3 (95 % CI, 1.39-1.88 × 10-3). We also combined data from previous studies to obtain comprehensive genetic values for the Korean population, and the average mutation rate was 1.59 × 10-3 (95 % CI, 1.38-1.82 × 10-3). Single-step mutations (95.69 %) and double-step mutations (3.35 %) were observed in the mutation pattern analysis, and cases expected to have multi-step mutations (0.96 %) were also observed. Large-sized alleles exhibited more loss mutations than gain mutations, and paternal mutations (62.68 %) were more frequently observed than maternal mutations (19.62 %). The calculated values and features of the 23 A-STRs explored in this study are expected to play a crucial role in establishing criteria for forensic genetic interpretation.

Determining the effects of genetic linkage when using a combination of STR and SNP loci for kinship testing

The pedigree likelihood ratio (LR) can be used for determining kinship in the forensic kinship testing. LR can be obtained by analyzing the DNA data of Short tandem repeat (STR) and single nucleotide polymorphism (SNP) loci. With the advancement of biotechnology, increasing number of genetic markers have been identified, thereby expanding the pedigree range of kinship testing. Moreover, some of the loci are physically closer to each other and genetic linkage between loci is inevitable. LRs can be calculated by accounting for linkage or ignoring linkage (LRlinkage and LRignore, respectively). GeneVisa is a software for kinship testing (www.genevisa.net) and adopts the Lander-Green algorithm to deal with genetic linkage. Herein, we used the simulation program of the software GeneVisa to investigate the effects of genetic linkage on 1st-degree, 2nd-degree, and 3rd-degree kinship testing. We used this software to simulate LRlinkage and LRignore values based on 43 STRs and 134 SNPs in commercial kits by using the allele frequency rate and genetic distance data of the European population. The effects of linkage on LR distribution and LRs of routine cases were investigated by comparing the LRlinkage values with the LRignore values. Our results revealed that the linkage effect on LR distributions is small, but the effect on LRs of routine cases may be large. Moreover, the results indicated that the discriminatory power of genetic markers for kinship testing can be improved by accounting for linkage.

A rare case of type II tri-allelic inheritance at vWA, SE33, D8S1179, and D13S317 loci demonstrated by STR analysis in paternity testing

Short tandem repeat (STR) typing has been regularly used in paternity disputes and forensic human identification linked caseworks. Occasionally, forensic scientists come across aberrant allele patterns during STR typing because of mutations, genetic variations, and other abnormalities. The tri-allelic pattern of STR is rare, particularly, the case where this pattern exists at 4 loci. Here, we report the type II tri-allelic patterns observed at vWA, SE33, D8S1179, and D13S317 loci in the product of conception (POC) sample during the course of our regular paternity case investigation. The DNA extracted from the blood samples and tissue of POC were subjected to STR typing for autosomal and sex STR loci using the commercial QIAGEN's Investigator® IDplex Plus Kit and QIAGEN's Investigator® 24plex QS Kit. Capillary electrophoresis was carried out in 3500 and 3500xL Genetic Analyzer Applied Biosystems and genotyped using GeneMapper ID-X Software v1.5 and v1.6. In this case of paternity inclusion, the POC sample displayed type II tri-allelic patterns at vWA (16, 19, 20), SE33 (19, 28.2, 29.2), D13S317 (16, 19, 20), and D8S1179 (10, 13, 17) loci. In addition, the POC displayed an abnormal genotype with a heterozygous peak imbalance (type II-B) of (1:2) pattern at D3S1358, D21S11, and D16S539 loci, of (2:1) pattern at D1S1656, D12S391, D10S1248, D2S1338, D2S441, D18S317, FGA, CSF1PO, and D5S818 loci, and type II-C allelic pattern (one single peak with triplicate height) at D19S433 and DS7820 loci. Understanding of such anomalous genotypes improves the knowledge about tri-allelic pattern of CODIS loci and helps in the appropriate interpretation of the results in STR typing.

Maternal uniparental disomy of chromosome 21 as a cause of pseudo-exclusion from paternity

Uniparental disomy (UPD) is a rare chromosomal condition, which apart from its importance in medical genetics can affect an outcome of parentage DNA testing, often causing pseudo exclusions. We describe a case of trio paternity test using 24 informative STR loci with potential exclusion at 2 systems located on chromosome 21. Consequent genotyping of an additional 25 autosomal and 27 Y-specific STRs revealed one other inconsistency, also located on this chromosome. All three inconsistent markers had the same heteroallelic state between the child and the biological mother providing evidence for maternal heterodisomy of chromosome 21. The case highlights the importance of considering UPD as a cause of genetic inconsistencies, especially when the inconsistent marker systems are located on the same chromosome.

A posteriori parameters from paternity tests of a Mexican laboratory with the powerplex fusion system

Population studies regarding Human identification (HID) systems report a priori forensic parameters, but rarely they describe a posteriori parameters from concluded paternity tests. We analyzed data from the PowerPlex® Fusion System in 1503 paternity tests from a Mexican laboratory for five years (2016-2020). The motherless duo paternity tests (89.8%) were more frequent than the standard trio tests (10.2%). A notable increase in motherless tests was noted regarding our previous report (89.8% vs 77.3%), probably explained by the COVID-19 pandemic. The estimated exclusion frequency in Mexico ranged from 30.1 (trio) to 32.1% (duo). For paternity exclusions, we report the number of mismatches and the frequency at which each STR was involved. The PowerPlex® Fusion system showed more than five mismatches in 100% of the standard trio tests excluding paternity, and the majority of motherless-duo tests (98.1%). In positive paternity tests, PowerPlex® Fusion offered a higher combined paternity index (PI) (average 1.18 E + 10) regarding HID systems with 15 and 20 STRs, even without the inclusion of the Y-linked locus DYS391 to the kinship interpretation. Individual and global STR mutation rates were estimated from 17 paternal mutations (μ = 0.0017), the majority involving a single-step mutation (94.11%). Five independent null alleles were detected, most of them involving the Penta E locus (80%), which suggests caution to the users working with DNA databases or kinship analysis, to avoid false exclusions with Penta E. In brief, our results provide a better overview of a posteriori informativeness offered by the PowerPlex® Fusion system for paternity testing in Mexico.

Paternity pseudo-exclusion caused by tetragametic chimerism in a gestational surrogacy case

Chimerism is a condition when an organism is composed of two or more populations of genetically distinct cells. Chimerism often produces curious results of medical and genetic investigations and could be a major cause of false negative conclusions in parentage testing. Here we describe a paternity pseudo-exclusion due to tetragametic chimerism in a gestational surrogacy case originated in a fertility clinic. Initial analysis using a buccal swab from the child and a peripheral blood sample from the father showed paternity exclusion at 6 STR loci. To find out the reason for observed paternal discrepancy father's semen sample used for IVF and samples from other tissues were genotyped. Buccal swabs, semen, hair follicles, nail clippings and cerumen showed identical mixed autosomal STR profiles originated from two genetically different cell lines and for all the 24 informative loci contain paternal obligate alleles. Results of Y-STR profiling of all paternal sample types showed a DNA profile originated from a single man. The mixed profiles obtained for different tissue types suggest that two genetically different cell lines contributed to formation of both the endoderm and the ectoderm of the father. The mesoderm seems to be monoclonal having originated from a genetically homogenous cell line as evidenced by the STR profile of peripheral blood. Such allelic pattern for various tissues suggests that the clonal origin happened at the very early stage of embryonic development. Approaches to minimise the rate of false exclusions in DNA parentage tests due to chimerism are discussed.

A 2b-RAD parentage analysis pipeline for complex and mixed DNA samples

Next-generation sequencing technology has revolutionized genotyping in many fields of study, yet parentage analysis often still relies on microsatellite markers that are costly to generate and are currently available only for a limited number of species. 2b-RAD sequencing (2b-RAD) is a DNA sequencing technique developed for ecological population genomics that utilizes type IIB restriction enzymes to generate consistent, uniform fragments across samples. This technology is inexpensive, effective with low DNA inputs, and robust to DNA degradation. Here, we developed a probabilistic genotyping-by-sequencing genetic testing pipeline for parentage analysis by using 2b-RAD for inferring familial relationships from mixed DNA samples and populations. Our approach to partial paternity assignment utilizes a novel weighted outlier paternity index (WOPI) adapted for next-generation sequencing data and an identity-by-state (IBS) matrix-based clustering method for pedigree reconstruction. The combination of these two parentage assignment methods overcomes two major obstacles faced by other genetic testing methods: 1) It allows detection of parentage when closely related or inbred individuals are in the alleged parent population (e.g., in laboratory strains); and 2) it resolves mixed DNA samples. We successfully demonstrate this novel approach by correctly inferring paternity for samples pooled from multiple offspring (i.e., entire clutches) in a highly inbred population of an East African cichlid fish. The unique advantages of 2b-RAD in combination with our bioinformatics pipeline enable straightforward and cost-effective parentage analysis in any species regardless of genomic resources available.

Calculation of the Paternity Index for STR with tri-allelic patterns in paternity testing

The calculation of the paternity index (PI) value of common bi-allelic genotypes at STR loci has been standardized in paternity cases. However, for tri-allelic patterns, a rare category of genotyping aberration in forensic practice, the statistical analysis in paternity testing remains disputed. The Type 1 tri-allelic pattern generally results from somatic mutation in the early stage of individual development. The Type 2 tri-allelic pattern is commonly generated by segmental duplication in the genome. In this study, practical and theoretical aspects of the evaluation of evidence concerning the Type 1 and Type 2 tri-allelic patterns in healthy individuals are discussed based on the likelihood ratio (LR) in different categories of kinship cases. The calculation of the PI value concerning tri-allelic genotypes is formulated according to the generation and genetic transmission of tri-allelic patterns. Meanwhile, a package tool named TriPI is developed to assist the calculation of the PI value in paternity testing concerning tri-allelic subjects, which could benefit the evaluation of the weight of evidence in the interpretation of tri-allelic pattern in forensic practice.

Selection and evaluation of bi-allelic autosomal SNP markers for paternity testing in Koreans

Due to the advantages of single-nucleotide polymorphisms (SNPs) in forensic science, many forensic SNP panels have been developed. However, the existing SNP panels have a problem that they do not reflect allele frequencies in Koreans or the number of markers is not sufficient to perform paternity testing. Here, we filtered candidate SNPs from the Ansan-Ansung cohort data and selected 200 SNPs with high allele frequencies. To reduce the risk of false inclusion and false exclusion, we calculated likelihood ratios of alleged father-child pairs from simulated families when the alleged father is the true father, the close relative of the true father, and the random man. As a result, we estimated that 160 SNPs were needed to perform paternity testing. Furthermore, we performed validation using Twin-Family cohort data. When 160 selected SNPs were used to calculate the likelihood ratio, paternity and non-paternity were accurately distinguished. Our set of 160 SNPs could be useful for paternity testing in Koreans.

The germlines of male monozygotic (MZ) twins: Very similar, but not identical

In 2012, a thought experiment in this journal suggested that paternity cases involving monozygotic (MZ) twins as putative fathers could be solved by means of whole genome sequencing (WGS). Although arising from a single fertilization event, MZ twins nevertheless continue to acquire somatic mutations during their development, including those that occur in the germline. Provided that paternity had been narrowed down to the twin pair beforehand by classical DNA analysis, one post-zygotic mutation would suffice to assign the paternal compartment of an offspring genome unambiguously to either twin if that mutation is found in the offspring and one twin, but not in the other twin. Since the publication of a proof-of-principle report in 2014, we have worked up five additional cases of MZ twin germline discrimination in real life, four paternity disputes and one criminal case requiring the identification of a sperm trace donor among a pair of MZ twin brothers. In this opinion paper, we report on the experiences made in the course of our work and take a look at possibilities for further development of the approach.

Preimplantation genetic testing as a component of root cause analysis of errors and reassignment of embryos in IVF

The risks of embryo/gamete mix-up are a threat to the integrity of the IVF process, with significant implications for affected families. The use of preimplantation genetic testing through single-nucleotide polymorphism array or next-generation sequencing technology can help to identify, characterize and ultimately help, in some cases, to find the root cause, and to mitigate the extent of these errors for a given patient or laboratory.

Factors influencing parentage ratio in canine dual-sired litters

Breeding a bitch with two different sires during a single estrous cycle has the potential to facilitate rapid genetic gain and improve reproductive performance within a canine breeding colony. There is limited data regarding the factors that contribute to the success of dual-sired litters in domestic dogs, and only anecdotal evidence suggesting that these litters rarely produce offspring from more than one sire. The objective of this prospective clinical study was to investigate multiple factors that likely affect the success of dual-sired litters on whelping rate, litter size and parentage ratio. These factors include: timing of artificial insemination (AI), order of sires, number of AI's per cycle, semen type, sperm quality and age of sire and bitch. Data collected over a 10 year period from twenty-nine estrous cycles (28 individual bitches of 10 different breeds) were evaluated after an initial AI with frozen semen from the 'genetically desired' sire and followed up with a second AI with either fresh (n = 9) or frozen (n = 16) semen or natural mating (n = 4) from a different, 'back up', sire. DNA parentage of each pup born was determined by using a primary panel of 288 SNPs. The whelping rate and litter size from previous single sire inseminations per estrous cycle, in the same bitches, (n = 16) over 25 estrous cycles using either fresh (n = 4) or frozen-thawed (n = 21) semen, were analyzed as controls. Of the 29 dual-sired breedings, 26 bitches whelped (89.7%), and 8 litters (30.8%) were of mixed parentage. In the litters of mixed parentage after a dual-sired breeding, a greater proportion of the offspring were from the second sire than the first sire (73.0% and 27.0% respectively; P < 0.05). Interestingly, in litters where all pups were of single sire parentage after a dual-sired breeding, 50.0% of the offspring were by the first sire and 50.0% were by the second sire. For litters of mixed or single paternity produced by dual-sired breeding there was no difference in average litter size. However, on a per estrous cycle basis for each bitch the whelping rate (89.7% v. 76.0%.) and litter size (5.5 ± 2.5 v. 4.0 ± 2.78) of all dual-sired breedings were greater (P < 0.05) compared to previous single-sired breedings (controls) respectively. This study demonstrates that offspring of mixed parentage derived from dual-sired breedings may be achieved. Furthermore, insemination with semen from two different sires may increase the whelping rate and litter size, which is an important consideration when using genetically valuable, or older individuals with potentially reduced fertility.

A four-step mutation at D22S1045 in one complex paternity case when the brother of the alleged father hypothesis is evaluated

We report one complex paternity case presenting a presumable paternal four-step STR mutation between the alleged father (AF) and child; the complexity of the case required the AF-brother hypothesis to be discarded without including this DNA sample. A total of 23 autosomal STR loci included in the Powerplex Fusion® and Globalfiler™ kits confirmed one isolated mismatch for D22S1045 between the AF (17/17) and the male child (13/15) in the presence of the mother (15/15). In this case, the STR structure and father's age do not seem to have contributed to promote the observed multistep mutation. The Paternity Index (PI) based on 23 autosomal STRs did not favor the AF paternity over the AF-brother hypothesis based on a flat prior (PI = 0.1217; W = 10.85%). For that reason, we included 38 autosomal human identification (HID) insertions-deletions (indels) and 20 retrotransposon insertion polymorphisms (RIPs) contained in the InnoTyper® 21 kit. Although these biallelic markers favored the AF paternity rather than the AF-brother hypothesis (LR = 110.3; W = 99.1%), the global PI based on 81 autosomal markers supported moderately the AF paternity hypothesis (LR = 13.4; W = 93.1%). The application of different mutation models showed a consistent support to the AF paternity hypothesis (PI = 93.1-99.95%), which could be useful for interpretation in these multistep STR mutation cases. In brief, we showed the impact of a four-step mutation at D22S1045 to obtain definitive paternity conclusions, particularly under a complex scenario when the AF-brother hypothesis is assessed. Forensic genomics arises as the next option for similar complex paternity cases.

Multiple methods used for type detection of uniparental disomy in paternity testing

Uniparental disomy (UPD) has attracted more attention recently in paternity testing, though it is an infrequent genetic event. Although short tandem repeat (STR) profiling has been widely used in paternity testing, it is not sufficient to use STR only to judge the genetic relationship, because the existence of UPD will inevitably affect the results of genotyping. Compared with complete UPD, segmental UPD is more difficult to detect because it does not affect all genotypes on the same chromosome. It is necessary to determine the type of UPD with multiple methods because a single method is not sufficient. Therefore, it is advisable to detect UPD in paternity testing with multiple methods. In this study, after autosomal STR profiling was used, we found that there were several gene loci on the same chromosome that did not conform to Mendelian genetic law, thus we highly suspected the existence of UPD and performed X-STR profiling immediately. Then whole-genome single nucleotide polymorphism (SNP) array analysis was performed to identify the type, and the results provided straightforward evidence for distinguishing complete from segmental UPD. Lastly, we used deletion insertion polymorphism (DIP)-SNP SNaPshot assay and Miseq FGx sequencing (for SNP and STR) to determine whether the mutation source is maternal uniparental disomy (mUPD) or paternal uniparental disomy (pUPD). To avoid false exclusion of kinship, it is vital to determine the type of UPD in paternity testing and effective strategies based on multiple methods to detect the type of UPD are provided in this study.

Slippage mutation rates in 15 autosomal short tandem repeat loci for forensic purposes in a Southeastern Brazilian population

Well-defined estimates of mutation rates in highly polymorphic tetranucleotide STR loci are a prerequisite for human identification in genetics laboratory routines useful for civil and criminal investigations. Studying 15 autosomal STR loci of forensic interest (CSF1PO, D2S1338, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D19S433, D21S11, FGA, TH01, TPOX, and vWA), we detected 193 slippage mutations (189 one-step and four two-step mutations) in 148 875 parent-child allelic transfers from 5171 paternity cases with true biological relationship (15 096 individuals; 4754 trios and 417 duos; 9925 meiosis) from the state of São Paulo, a very representative population of Brazil. The overall mutation rate was 1.3 × 10^-3 and the highest rates were observed at loci vWA (2.8 × 10^-3 ), FGA and D18S51 (2.7 × 10^-3 for both), while loci TH01 and TPOX did not present any mutations. The mean slippage mutation rate of paternal origin (1.8 × 10^-3 ) was six times higher than that observed for maternal origin (0.3 × 10^-3 ).

Development of a new 25plex STRs typing system for forensic application

We have developed a novel STR 25-plex florescence multiplex-STR kit (DNATyper25) to genotype 23 autosomal and two sex-linked loci for forensic applications and paternity analysis. Of the 23 autosomal loci, 20 are non-CODIS. The sex-linked markers include a Y-STR locus (DYS391) and the Amelogenin gene. We present developmental validation studies to show that the DNATyper25 kit is reproducible, accurate, sensitive, and robust. Sensitivity testing showed that full profiles were achieved with as low as 125 pg of human DNA. Specificity testing demonstrated a lack of cross reactivity with a variety of commonly encountered non-human DNA contaminants. Stability testing showed that full profiles were obtained with humic acid concentration ≤60 ng/μL and hematin concentration <400 μM. For forensic evaluation, the 23 autosomal STRs followed the Hardy-Weinberg equilibrium. In an analysis of 509 Chinese (CN) Hans, we detected a combined total of 181 alleles at the 23 autosomal STR loci. Since these autosomal STRs are independent from one another, PM was 8.4528 × 10^-22 , TDP was 0.999 999 999 999 999 999 999, CEP was 0.999 999 8395. The forensic efficiency parameters demonstrated that these autosomal STRs are highly polymorphic and informative in the Han population of China. We performed population comparisons and showed that the Northern CN Han has a close genetic relationship with the Luzhou Han, Tujia, and Bai populations. We propose that the DNATyper25 kit will be useful for cases where paternity analysis is difficult and for situations where DNA samples are limited in quantity and low in quality.

Maternal uniparental isodisomy for chromosome 6 discovered by paternity testing: a case report

Background

Uniparental disomy (UPD) is a rare condition in which a child inherits both copies of a chromosome or chromosome segment from one parent. Medical consequences of UPD may include abnormal imprinting, unmasking of genetic disease, and somatic mosaicism; alternatively, the condition may be clinically silent. We present a case of maternal UPD for chromosome 6, a rare condition previously reported less than 20 times. In our patient with a normal phenotype, the condition was discovered through abnormal paternity testing results. Uniparental isodisomy is a rare cause of discordant parentage testing results, but it is an important phenomenon to recognize.

Case presentation

We present a female born at 32 weeks gestational age with birth weight 10–25%ile when corrected for prematurity. Paternity testing was obtained for legal reasons, and initial results appeared to exclude the alleged father. However, the lab performed additional testing which indicated that the patient was homozygous for maternal alleles for all three tested loci located on chromosome 6. Based on these results, the patient was referred for a medical genetics evaluation for possible maternal uniparental disomy. She presented for her consultation at 10 months of age and appeared to be developing appropriately. Her age-adjusted weight, length, and head circumference were <3%ile, 10%ile, and 25%ile respectively. Chromosomal microarray testing confirmed maternal UPD6. The patient was seen again at 14 months of age, and her weight and length were 10–25%ile. She had not developed concerning symptoms or physical exam findings.

Conclusions

The presence of UPD, especially in asymptomatic patients, has implications for paternity testing, as standard methods may miss cases of both isodisomy and heterodisomy. This rare inheritance pattern should be considered when discordant paternity results come under suspicion. It is unusual for a parentage testing lab to perform the amount of testing done for this case, but the initial inconsistencies necessitated further investigation. UPD6 has uncertain effects and variable phenotypes, so this patient’s genetic abnormality likely would have gone undiscovered if not for the non-medical indication for the laboratory analysis. Her asymptomatic presentation raises the possibility that UPD may be more common than previously estimated.

Paternity testing using massively parallel sequencing and the PowerSeq™ AUTO/Y system for short tandem repeat sequencing

Massively parallel sequencing (MPS) is gaining attention as a new technology for routine forensic casework, including paternity testing. Recently released MPS multiplex panels provide many more loci compared to CE methods, plus provide sequence-based alleles that together improve the statistical power of the genetic testing. Here, an MPS system (PowerSeq™ AUTO/Y) was applied for STR sequencing in the study of first-degree STR sequence allele inheritance from families in Southern Brazil. In 29 trios (mother-child-father) analyzed, the paternity index values generally increased when data from sequence-based analysis were used in comparison to length-based data. Further, allele inconsistencies (e.g., single repeat mutation events) between child and parents could be resolved with MPS by assessing the core repeat and flanking region sequences. Lastly, the sequence information allowed for identification of isoalleles (alleles of the same size, but different sequence) to determine specific paternal and maternal inheritances. The results from this study showed advantages of implementing sequence-based analysis, MPS, in paternity testing with improved statistical calculations and a greater resolution for the trios/families tested.

Analysis of fetal DNA in maternal plasma with markers designed for forensic DNA mixture resolution

PURPOSE

With the description of circulating fetal DNA in maternal blood, noninvasive prenatal diagnostics became theoretically possible. As the presence of background maternal DNA interferes with the detection of fetal DNA, analytical methods require genetic markers capable of distinguishing by quantitative or targeted approaches the minor population of DNA molecules of the fetus. Here we evaluate the feasibility of analyzing fetal DNA with novel DIP-STR genetic markers, designed for the investigation of forensic mixed biological evidence.

METHODS

The DIP-STR molecular approach is based on sequence-specific analysis of paternally inherited fetal alleles. These sequences are biallelic deletion/insertion polymorphisms (DIPs) located very close to short tandem repeat (STR) markers, for combined analysis. In this study, 48 women were tested with 28 DIP-STRs during the first, second, and third trimester of pregnancy.

RESULTS

Positive results were obtained across markers, including longer ones (386 base-pairs) and with blood samples collected during early pregnancy, such as 10 weeks of gestational age.

CONCLUSION

These data show that DIP-STR markers can be used to amplify specific genomic regions of circulating fetal DNA to obtain targeted genetic information. This method may contribute to developments in noninvasive prenatal paternity testing and diagnosis of certain genetic diseases.

Mutation analysis of short tandem repeats in a population sample from Upper Silesia (southern Poland)

In paternity testing, DNA polymorphism analysis not only settles explicitly disputed paternity issue but also provides information on mutation frequencies in STR loci. In this study, insertion or deletion of one repetitive unit was observed in 38 of 32,391 meiotic transfers analysed in 953 paternity testing cases. Parentage samples from Upper Silesia (southern Poland) were examined in 2008-2014 with the use of three commercially available amplification kits: AmpFlSTR Identifiler (Applied Biosystems), PowerPlex 16 HS (Promega) and PowerPlex ESX 17 (Promega). The rate of paternal mutations was 4.6 times higher than that of maternal ones. The highest mutation rate was noted at VWA locus. Interpopulation comparisons showed statistically significant differences in mutation rates of several STRs between Upper Silesia and populations from Brazil and China. There were no differences in occurrence of mutations between a population from Upper Silesia and another southern Polish population from a region of Lesser Poland. Our results suggest that knowledge of STR mutation rates in different populations may be important for calculations of probability of relationship in disputed paternity testing and that such calculations should be based on population-specific mutation rates, at least for some STR markers used commonly in forensic genetics.

Paternity tests in Mexico: Results obtained in 3005 cases

National and international reports regarding the paternity testing activity scarcely include information from Mexico and other Latin American countries. Therefore, we report different results from the analysis of 3005 paternity cases analyzed during a period of five years in a Mexican paternity testing laboratory. Motherless tests were the most frequent (77.27%), followed by trio cases (20.70%); the remaining 2.04% included different cases of kinship reconstruction. The paternity exclusion rate was 29.58%, higher but into the range reported by the American Association of Blood Banks (average 24.12%). We detected 65 mutations, most of them involving one-step (93.8% and the remaining were two-step mutations (6.2%) thus, we were able to estimate the paternal mutation rate for 17 different STR loci: 0.0018 (95% CI 0.0005-0.0047). Five triallelic patterns and 12 suspected null alleles were detected during this period; however, re-amplification of these samples with a different Human Identification (HID) kit confirmed the homozygous genotypes, which suggests that most of these exclusions actually are one-step mutations. HID kits with ≥20 STRs detected more exclusions, diminishing the rate of inconclusive results with isolated exclusions (<3 loci), and leading to higher paternity indexes (PI). However, the Powerplex 21 kit (20 STRs) and Powerplex Fusion kit (22 STRs) offered similar PI (p = 0.379) and average number of exclusions (PE) (p = 0.339) when a daughter was involved in motherless tests. In brief, besides to report forensic parameters from paternity tests in Mexico, results describe improvements to solve motherless paternity tests using HID kits with ≥20 STRs instead of one including 15 STRs.

Applying massively parallel sequencing to paternity testing on the Ion Torrent Personal Genome Machine

Massively parallel sequencing (MPS) is a promising supplementary method for forensic genetics and has gradually been applied to forensic casework. In this study, we applied MPS to forensic casework on an Ion Torrent Personal Genome Machine to evaluate its performance in paternity testing with mismatched STR loci. A total of 15 samples from seven cases containing one mismatched locus by capillary electrophoresis typing were analyzed. Combined paternity index (CPI) and relative chance of paternity were calculated according to the International Society for Forensic Genetics guidelines and the Chinese national standards recommended for paternity testing. With simultaneous analysis of enough STR loci, the results support the certainty of paternity, and the mismatched alleles were considered to be mutations (CPI>10,000). With the detection of allele sequence structures, the origins of the mutations were inferred in some cases. Meanwhile, nine STRs (CSF1PO, D1S1656, D2S441, D2S1338, D3S1358, D8S1179, D12S391, D21S11 and D4S2408) were found in an increased number of unique alleles and three new alleles in three STRs (D2S441, D21S11, and FGA) that have not been reported before were detected. Therefore, MPS can provide valuable information for forensic genetics research and play a promising role in paternity testing.

Paternity testing at the Department of Forensic Medicine of Wroclaw Medical University (Poland)

Evidentiary materials in court cases comprise the testimony of all relevant parties and witnesses, physical and biological evidence, and the stage of child's development at the moment of birth. In this study, an analysis was made of results obtained between 1966 and 2014 from paternity testing capable of providing biological evidence for court cases. During this time, 16,508 opinions were released, with exclusion of paternity in 4182 cases. The analysis of the total percentage of exclusions in individual years over the entire period of 49years turned out to be very interesting. Initially, there was a high percentage of exclusions, which most likely resulted from women wrongfully accusing men; however, this figure stabilised in the twenty-first century at less than 20%.

SNP Markers as Additional Information to Resolve Complex Kinship Cases

BACKGROUND

DNA profiling with sets of highly polymorphic autosomal short tandem repeat (STR) markers has been applied in various aspects of human identification in forensic casework for nearly 20 years. However, in some cases of complex kinship investigation, the information provided by the conventionally used STR markers is not enough, often resulting in low likelihood ratio (LR) calculations. In these cases, it becomes necessary to increment the number of loci under analysis to reach adequate LRs. Recently, it has been proposed that single nucleotide polymorphisms (SNPs) could be used as a supportive tool to STR typing, eventually even replacing the methods/markers now employed.

METHODS

In this work, we describe the results obtained in 7 revised complex paternity cases when applying a battery of STRs, as well as 52 human identification SNPs (SNPforID 52plex identification panel) using a SNaPshot methodology followed by capillary electrophoresis.

RESULTS

Our results show that the analysis of SNPs, as complement to STR typing in forensic casework applications, would at least increase by a factor of 4 total PI values and correspondent Essen-Möller's W value.

CONCLUSIONS

We demonstrated that SNP genotyping could be a key complement to STR information in challenging casework of disputed paternity, such as close relative individualization or complex pedigrees subject to endogamous relations.

Concurrent copy number variations on chromosome 8 and 22 combined with mutation at FGA locus revealed in a parentage testing case

Copy number variations (CNVs) are one of the major sources of human genetic diversity and are associated with rare genomic disorders as well as complex traits and diseases. A copy number variation was observed at the D8S1179 locus during routine STR based parentage testing, in which the child exhibited three alleles, "13, 15, 16", with the putative father a homozygous "15" and the mother homozygous "13". In addition, in the same testing case, there was a one-step mutation at the STR locus FGA, in which the putative father was a "22, 24", the mother was a "22, 25", and the child was a "22, 23". After further investigations by re-amplified with different primer sets, clone-based sequencing, karyotype analysis and whole-genome SNP analysis, the results showed that the child had the CNVs at chromosome 8q24.3 and 22q11.21. In conclusion, for parentage testing cases encountered with tri-allele patterns, more testings, such as cloning sequencing, karyotyping, or even whole genome analysis, as well as more appropriate statistical estimations might be conducted to further confirm or exclude the relationship.

Multistep microsatellite mutation leading to father-child mismatch of FGA locus in a case of non-exclusion parentage

A non-exclusion paternity case with a mismatch in the autosomal short tandem repeats (STR) locus FGA is reported. The genotypes of the suspected father, the mother and the questioned child in FGA locus were 18/25, 20/26 and 20/22, respectively. Examination of 38 autosomal STR loci revealed no mismatches, and the paternity index is up to 1.3618×10(6). The haplotype of 16 Y chromosomal STR in the child matched completely with that of the father. These results suggested that the suspected father is the biological father of the child and that a rare three- or four-step microsatellite mutation had occurred in the paternal allele of FGA.

Establishment of a microsatellite set for noninvasive paternity testing in free-ranging Macaca mulatta tcheliensis in Mount Taihangshan area, Jiyuan, China

BACKGROUND

Within multi-male and multi-female mammalian societies, paternity assignment is crucial for evaluating male reproductive success, dominance hierarchy, and inbreeding avoidance. It is, however, difficult to determine paternity because of female promiscuity during reproduction. Noninvasive molecular techniques (e.g., fecal DNA) make it possible to match the genetic father to his offspring. In the current study, a troop of free-ranging Taihangshan macaques (Macaca mulatta tcheliensis) in Mt. Taihangshan area, Jiyuan, China, was selected for studying the paternity. We successfully screened a set of microsatellite loci from fecal DNA and evaluated the efficiency of these loci for paternity testing using clearly recorded data of maternity.

RESULTS

The results showed that: 1) ten loci out of 18 candidate microsatellite loci were amplified successfully in the fecal samples of Taihangshan macaques. The error probability in maternity assignments and paternity testing was very low as indicated by their power of discrimination (0.70 to 0.95), power of exclusion (0.43 to 0.84), and the values of polymorphic information content ranging from 0.52 to 0.82; 2) the combined probability of exclusion in paternity testing for ten qualified loci was as high as 99.999%, and the combined probability of exclusion reached 99.99% when the seven most polymorphic loci were adopted; 3) the offspring were assigned to their biological mother correctly and also matched with their genetic father.

CONCLUSIONS

We concluded that the ten polymorphic microsatellite loci, especially a core set of seven most polymorphic loci, provided an effective and reliable tool for noninvasive paternity testing in free-ranging rhesus macaques.

Usefulness of SNPs as Supplementary Markers in a Paternity Case with 3 Genetic Incompatibilities at Autosomal and Y Chromosomal Loci

BACKGROUND

In kinship testing, investigation of 15 short tandem repeats (STRs) usually provides decisive genetic information for resolving relationship cases. However, in complex deficiency cases, in cases with more than 2 mutations at different STR loci or when close (untested) relatives of the alleged father are suggested to be the biological father of the child, STR typing alone may not be sufficient. In these cases, the application of supplementary markers such as single nucleotide polymorphisms (SNPs) is recommended.

METHODS

We describe a paternity case with 3 genetic incompatibilities (Penta D, VWA, and DYS385) between the alleged father and the child after analyzing 23 autosomal and 16 Y chromosomal STR loci. The question arose as to whether the alleged father could be excluded and a related person could be the biological father of the child, or whether the observed genetic incompatibilities were mutations. Interestingly, the 2 excluded full brothers of the alleged father possessed identical genetic incompatibilities at locus VWA and DYS385 as the alleged father.

RESULTS AND CONCLUSIONS

Additional performance of a 50-plex SNP assay demonstrated that the observed mismatches were indeed mutations and the alleged father was the biological father of the child. The results show the usefulness of SNPs as supplementary markers in relationship testing when STR analyses show ambiguous results.

[Extrapair paternity in Parus major]

Mating systems, as an evolutionary stable strategy, play an important role in animal reproductive process and result from an animal's adaption to their environment, including their inter-specific environment. In the 1980s, extrapair paternity (EPP) was first noted in the eurychoric species, the Great Tit, Parus major. As earlier studies indicated, morphology, physiology, behavior, ecological characteristics and mating systems of eurychoric species differ greatly between areas or populations. Accordingly, we analyzed the mating system of the Great Tit (P.m.minor) in Fairy Cave National Nature Reserve, Liaoning, China. We collected total parent-offspring blood samples from 22 broods. We used 8 hypervariable loci, which were selected from 11 reported microsatellite loci for paternity test. In conjunction with the known genetic pattern of the female parent, the accuracy of the paternity testing reached 99.98% with this genetic data. Results of paternity testing showed that 7 of 22 broods (31.8%) had extra-pair nestling, with 16 of 197 nestlings (8.12%) a result of extra-pair fertilizations. The EPP rate of the Great Tit we noted in Liaoning is obviously lower than those in other passerine forest birds (less than 10%). Though between 55.6% and 9.1% extrapair offspring were found among the different nests, we were, however, unable to find any explanatory rule.