Validation of a male-specific, 12-locus fluorescent short tandem repeat (STR) multiplex

Y chromosome-specific short tandem repeat (Y-STR) analysis has become another widely accepted tool for human identification. The PowerPlex Y System is a fluorescent multiplex that includes the 12 loci: DYS19, DYS385a/b, DYS389I/II, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438 and DYS439. This panel of markers incorporates the 9-locus European minimal haplotype (EMH) loci recommended by the International Y-STR User Group and the 11-locus set recommended by the Scientific Working Group on DNA Analysis Methods (SWGDAM). Described here are inter-laboratory results from 17 developmental validation studies of the PowerPlex Y System and include the following results: (a) samples distributed between laboratories and commercial standards produced expected and reproducible haplotypes; (b) use of common amplification and detection instruments were successfully demonstrated; (c) full profiles were obtained with standard 30 and 32 cycle amplification protocols and cycle number (24-28 cycles) could be modified to match different substrates (such as direct amplification of FTA paper); (d) complete profiles were observed with reaction volumes from 6.25 to 50 microL; (e) minimal impact was observed with variation of enzyme concentration; (f) full haplotypes were observed with 0.5-2x primer concentrations; however, relative yield between loci varied with concentration; (g) reduction of magnesium to 1mM (1.5 mM standard) resulted in minimal amplification, while only partial loss of yield was observed with 1.25 mM magnesium; (h) decreasing the annealing temperature by 2-4 degrees C did not generate artifacts or locus dropout and most laboratories observed full amplification with the annealing temperature increased by 2 degrees C and significant locus dropout with a 4 degrees C increase in annealing temperature; (i) amplification of individual loci with primers used in the multiplex produced the same alleles as observed with the multiplex amplification; (j) all laboratories observed full amplification with >or = 125 pg of male template with partial and/or complete profiles observed using 30-62.5 pg of DNA; (k) analysis of < or = 500 ng of female DNA did not yield amplification products; (l) the minor male component of a male/female mixture was observed with < or =1200-fold excess female DNA with the majority of alleles still observed with 10,000-fold excess female; (m) male/male mixtures produced full profiles from the minor contributor with 10-20-fold excess of the major contributor; (n) average stutter for each locus; (o) precision of sizing were determined; (p) human-specificity studies displayed amplification products only with some primate samples; and (q) reanalysis of 102 non-probative casework samples from 65 cases produced results consistent with original findings and in some instances additional identification of a minor male contributor to a male/female mixture was obtained. In general, the PowerPlex Y System was shown to have the sensitivity, specificity and reliability required for forensic DNA analysis.     

Validation of male-specific, 12-locus fluorescent short tandem repeat (STR) multiplex

Y chromosome-specific short tandem repeat (Y-STR) analysis has become another widely accepted tool for human identification. The PowerPlex Y System is a fluorescent multiplex that includes the 12 loci: DYS19, DYS385a/b, DYS389I/II, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438 and DYS439. This panel of markers incorporates the 9-locus European minimal haplotype (EMH) loci recommended by the International Y-STR User Group and the 11-locus set recommended by the Scientific Working Group on DNA Analysis Methods (SWGDAM). Described here are inter-laboratory results from 17 developmental validation studies of the PowerPlex Y System and include the following results: (a) samples distributed between laboratories and commercial standards produced expected and reproducible haplotypes; (b) use of common amplification and detection instruments were successfully demonstrated; (c) full profiles were obtained with standard 30 and 32 cycle amplification protocols and cycle number (24-28 cycles) could be modified to match different substrates (such as direct amplification of FTA paper); (d) complete profiles were observed with reaction volumes from 6.25 to 50 microL; (e) minimal impact was observed with variation of enzyme concentration; (f) full haplotypes were observed with 0.5-2x primer concentrations; however, relative yield between loci varied with concentration; (g) reduction of magnesium to 1mM (1.5 mM standard) resulted in minimal amplification, while only partial loss of yield was observed with 1.25 mM magnesium; (h) decreasing the annealing temperature by 2-4 degrees C did not generate artifacts or locus dropout and most laboratories observed full amplification with the annealing temperature increased by 2 degrees C and significant locus dropout with a 4 degrees C increase in annealing temperature; (i) amplification of individual loci with primers used in the multiplex produced the same alleles as observed with the multiplex amplification; (j) all laboratories observed full amplification with >or = 125 pg of male template with partial and/or complete profiles observed using 30-62.5 pg of DNA; (k) analysis of < or = 500 ng of female DNA did not yield amplification products; (l) the minor male component of a male/female mixture was observed with < or =1200-fold excess female DNA with the majority of alleles still observed with 10,000-fold excess female; (m) male/male mixtures produced full profiles from the minor contributor with 10-20-fold excess of the major contributor; (n) average stutter for each locus; (o) precision of sizing were determined; (p) human-specificity studies displayed amplification products only with some primate samples; and (q) reanalysis of 102 non-probative casework samples from 65 cases produced results consistent with original findings and in some instances additional identification of a minor male contributor to a male/female mixture was obtained. In general, the PowerPlex Y System was shown to have the sensitivity, specificity and reliability required for forensic DNA analysis.     

Testing and evaluation of 43 "noncore" Y chromosome markers for forensic casework applications

A developmental validation study was performed on three Y-STR multiplex systems, Multiplex III (MPIII), Multiplex IV (MPIV), and Multiplex V (MPV), to ascertain their potential applicability to forensic casework. MPIII contains eight Y-STRs, including DYS426, DYS435, DYS436, DYS441, DYS442, DYS446, DYS462, and Y-GATA-A10, and one InDel, YAP (DYS287). MPIV contains 21 Y-STR loci, including DYS443, DYS444, DYS445, DYS447, DYS448, DYS449, DYS452, DYS453, DYS454, DYS455, DYS456, DYS458, DYS463, DYS464, DYS468, DYS484, DYS522, DYS527, DYS531 DYS557, and DYS588. MPV contains 13 Y-STR loci, including DYS459, DYS476, DYS488, DYS513, DYS549, DYS561, DYS570, DYS575, DYS576, DYS590, DYS594, DYS598, and DYS607. Full genetic profiles were consistently obtained for all three multiplexes with 25-50 pg of male DNA. No significant amplification was observed with 1 mug of female DNA. Each multiplex permitted the determination of the number of male donors in male:male DNA admixtures. Species specificity studies demonstrated some cross-reactivity with some primate samples. Environmentally compromised blood samples produced full or partial profiles after exposure to various conditions for up to 1 year. Full profiles were recovered from simulated casework specimens including cigarette butts and postcoital cervicovaginal swabs. Population data were collected to determine individual loci gene diversity and multiplex discriminatory capacity.     

SWGDAM developmental validation of a 19-locus Y-STR system for forensic casework

A Scientific Working Group on DNA Analysis Methods (SWGDAM) developmental validation study was carried out on two Y-STR multiplex systems (MPI and MPII) that collectively permit the co-amplification of 19 Y-STR markers, including DYS393, DYS392, DYS391, DYS389I, DYS389II, Y-GATA-A7.2 (DYS461), DYS438, DYS385a and DYS385b (MPI); DYS425, DYS388, DYS390, DYS439, DYS434, DYS437, Y-GATA-C.4, Y-GATA-A7.1 (DYS460), Y-GATA-H.4, and DYS 19 (MPII). Performance checks subsequent to PCR parameter optimization indicated that MPI and MPII were suitably reproducible, precise and accurate for forensic use. The sensitivity of the systems was such that a full 19-locus Y-STR profile was obtainable with 150-200 pg of male DNA, and some loci were detectable even with as little as 20-30 pg of input DNA. Primate specificity was demonstrated by the lack of cross-reactivity with a variety of commonly encountered bacterial and animal species, with the single exception of a monomorphic canine product that was outside of the size range of human alleles from any of the 19 loci. Not surprisingly, cross-reactivity was observed with a number of male and female nonhuman primates. Environmentally compromised samples produced full or partial Y-STR profiles. For example, a semen stain exposed to the outdoor elements for six months still gave a 13-locus Y-STR profile. Although a limited number of female DNA artifacts were observed in mixed stains in which the male DNA comprised 1/300 of the total, the full 19-locus male profile was easily discernible. Even at a 1500-to-2000-fold dilution of male DNA with female DNA partial Y-STR profiles were obtained. Furthermore, the potential utility of MPI and MPII for forensic casework is exemplified by their ability to dissect out the male haplotype in a variety of case-type samples, including, inter alia, post-coital vaginal swabs, admixed male and female bloodstains, the nonsperm fraction from a differentially extracted semen stain, and determination of the number of male donors in mixed semen stains.     

Internal Validation of the AmpFlSTR Yfiler™ Amplification Kit for Use in Forensic Casework

Abstract:  Y-chromosomal short-tandem repeat (Y-STR) amplification has been used in forensic casework at the Bureau of Criminal Apprehension (BCA) Forensic Science Laboratory since 2003. At that time, two separate amplifications were required to type the SWGDAM recommended loci (DYS19, DYS385a/b, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS438, and DYS439). The Yfiler™ kit coamplifies these loci as well as DYS437, DYS448, DYS456, DYS458, DYS635, and Y GATA H4. The Yfiler™ kit was validated following the internal validations outlined in the SWGDAM revised validation guidelines. Our studies show that 0.125 ng of male DNA will generate a complete 17 locus profile and that as little as 0.06 ng of male DNA yields an average of nine loci. In the male–male mixtures, a complete profile from the minor component was detected up to 1:5 ratio; most of the alleles of the minor component were detected at a 1:10 ratio and more than half the alleles of the minor component were detected at a 1:20 ratio. Complete YSTR profiles were obtained when 500 pg male DNA was mixed with female DNA at ratios up to 1:1000. At ratios of 1:5000 and 1:10,000 (male DNA to female DNA) inhibition of the YSTR amplification was evident. The YSTR results obtained for the adjudicated case samples gave significantly more probative information than the autosomal results. Our studies demonstrate that the Yfiler™ kit is extremely sensitive, does not exhibit cross-reactivity with female DNA, successfully types male DNA in the presence of overwhelming amounts of female DNA and is successful in typing actual forensic samples from adjudicated cases.     

Internal validation of the AmpFlSTR Yfiler amplification kit for use in forensic casework.

Y-chromosomal short-tandem repeat (Y-STR) amplification has been used in forensic casework at the Bureau of Criminal Apprehension (BCA) Forensic Science Laboratory since 2003. At that time, two separate amplifications were required to type the SWGDAM recommended loci (DYS19, DYS385a/b, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS438, and DYS439). The Yfiler kit coamplifies these loci as well as DYS437, DYS448, DYS456, DYS458, DYS635, and Y GATA H4. The Yfiler kit was validated following the internal validations outlined in the SWGDAM revised validation guidelines. Our studies show that 0.125 ng of male DNA will generate a complete 17 locus profile and that as little as 0.06 ng of male DNA yields an average of nine loci. In the male-male mixtures, a complete profile from the minor component was detected up to 1:5 ratio; most of the alleles of the minor component were detected at a 1:10 ratio and more than half the alleles of the minor component were detected at a 1:20 ratio. Complete YSTR profiles were obtained when 500 pg male DNA was mixed with female DNA at ratios up to 1:1000. At ratios of 1:5000 and 1:10,000 (male DNA to female DNA) inhibition of the YSTR amplification was evident. The YSTR results obtained for the adjudicated case samples gave significantly more information than the autosomal results. Our studies demonstrate that the Yfiler kit is extremely sensitive, does not exhibit cross-reactivity with female DNA, successfully types male DNA in the presence of overwhelming amounts of female DNA and is successful in typing actual forensic samples from adjudicated cases.     

Internal validation study of the PowerPlex® Y23 system

The PowerPlex Y23 System is a 23-loci, 5-color Y-STR multiplex designed for genotyping forensic casework samples, database samples and paternity samples. The kit contains: all 12 loci in the current PowerPlex Y System, the additional 5 loci found in AmpFlSTR Y-filer, plus 6 new loci. An internal validation study of the PowerPlex Y23 kit was therefore conducted including the following aspects: sensitivity, mixture studies of male–male and female–male DNA, performance with simulated inhibition and stutter calculations. 100 Caucasians living in Switzerland were also typed using the PowerPlex Y23 kit.     

A Study of the Background Levels of Male DNA on Underpants Worn by Females

This study is the first to examine the background level of male DNA on underpants worn by females in the absence of sexual contact. Here, we examined 103 samples from the inside front of underpants from 85 female volunteers. Samples were examined for the presence of male DNA using NGM SElect and PowerPlex Y23 kits. Only five samples gave a “complete” Y-STR profile, even though 83.5% of our volunteers cohabited with a male. In all cases where a partner reference sample was available, the Y-STR profile matched the cohabiting partner. We have demonstrated that a Y-STR profile is not expected on the inside front of underpants worn by females after social contact alone. The results of this study are informative for evaluating the significance of a Y-STR profile on underpants in cases of alleged sexual assault.     

Y-chromosome STR haplotypes in Danes

A total of 185 unrelated Danish males were typed for the Y-chromosome STRs DYS19, DYS385a/b, DYS389-I, DYS389-II, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438 and DYS439 using the kits PowerPlex Y (Promega), ReliaGene Y-Plex 6 and ReliaGene Y-Plex 5 (Reliagene Technologies). A total of 163 different haplotypes were observed and among these, 144 haplotypes were unique. The gene diversity was 0.9985. In DYS392, a variant allele migrating as a 10.2 allele was observed. Sequencing of the allele showed a deletion upstream the repeated area.     

Development and validation of the AmpFlSTR Yfiler PCR amplification kit: a male specific, single amplification 17 Y-STR multiplex system

In the past 5 years, there has been a substantial increase in the use of Y-short tandem repeat loci (Y-STRs) in forensic laboratories, especially in cases where typing autosomal STRs has met with limited success. The AmpFlSTR Yfiler PCR amplification kit simultaneously amplifies 17 Y-STR loci including the loci in the "European minimal haplotype" (DYS19, DYS385a/b, DYS389I, DYS389II, DYS390, DYS391, DYS392, and DYS393), the Scientific Working Group on DNA Analysis Methods (SWGDAM) recommended Y-STR loci (DYS438 and DYS439), and the highly polymorphic loci DYS437, DYS448, DYS456, DYS458, Y GATA H4, and DYS635 (formerly known as Y GATA C4). The Yfiler kit was validated according to the FBI/National Standards and SWGDAM guidelines. Our results showed that full profiles are attainable with low levels of male DNA (below 125 pg) and that under optimized conditions, no detectable cross-reactive products were obtained on human female DNA, bacteria, and commonly encountered animal species. Additionally, we demonstrated the ability to detect male specific profiles in admixed male and female blood samples at a ratio of 1:1000.     

Y-chromosome STR system, Y-PLEX 12, for forensic casework: development and validation

The Y-PLEX 12 system, developed for use in human identification, enables simultaneous amplification of eleven polymorphic short tandem repeat (STR) loci, namely DYS392, DYS390, DYS385 a/b, DYS393, DYS389I, DYS391, DYS389II, DYS 19, DYS439 and DYS438, residing on the Y chromosome and Amelogenin. Amelogenin provides results for gender identification and serves as internal control for PCR. The validation studies were performed according to the DNA Advisory Board's (DAB) Quality Assurance Standards. The minimal sensitivity of the Y-PLEX 12 system was 0.1 ng of male DNA. The mean stutter values ranged between 3.76-15.72%. A full male profile was observed in mixture samples containing 0.5 ng of male DNA and up to 400 ng of female DNA. Amelogenin did not adversely affect the amplification of Y-STRs in mixture samples containing male and female DNA. The primers for the Y-STR loci present in Y-PLEX 12 are specific for human DNA and some higher primates. None of the primate samples tested provided a complete profile at all 11 Y-STR loci amplified with the Y-PLEX 12 system. Y-PLEX 12 is a sensitive, valid, reliable, and robust multiplex system for forensic analysis, and it can be used in human forensic and male lineage identification cases.     

Evaluation of usefulness of further Y-STR analysis in sexual assault cases on PSA positive samples resulting in female autosomal STR profiling

Samples from male to female sexual assault cases that are positive for the presumptive prostate specific antigen (PSA) test often do not result in a male autosomal STR profile. Due to highly unequal proportions of female and male DNA in typical sexual assault samples, routine autosomal STR analysis often fails to detect the DNA of the assailant, even after differential extraction of the samples. Previous studies have already shown the value of Y-STR analysis in such cases [1]. In Belgium, forensic DNA laboratories are only allowed to perform Y-STR profiling on sexual assault samples by a specific requisition, after routine autosomal STR analysis has been performed. However, a request for additional Y-STR analysis is rather exceptional.In this study, we evaluated the usefulness of further Y-STR analysis. For 100 PSA positive rinses and swabs from male to female sexual assault cases resulting in female autosomal STR profiling, 7% resulted in a full or partial Y-STR profile useful for comparison, using the 23-loci Y-STR PowerPlex Y23 System (Promega). The success rate raised to 12.5% with a higher DNA input in the PCR mix. In conclusion, these results support the usefulness of performing Y-STRs analysis on the sperm DNA extracts to identify the alleged assailant in sexual assault cases.     

Unexpected patterns in Y-STR analyses and implications for profile identification

Y-STR analysis is widely used in many fields, such as paternity testing, genealogy studies and in male/female mixtures. In many rape cases, Y-STRs are also useful for the determination of contributors’ number. Here we described a father/son pair with double peaks at DYS439 and DYS635 loci. This case should focus the attention on forensic interpretation of Y-haplotype profiles, because multiple alleles at various loci do not forcibly indicate that the sample originates from a mixture.We also report a case of two half-brothers with null allele at DYS448.Since DYS439 and DYS635 loci are located in the AZFa region and DYS448 locus in the AZFc region, we performed a molecular genetics study of these regions to evaluate a possible correlation between Y-STR profiles and Y chromosome deletions involved in infertility.     

Y-STR profiling in extended interval (> or = 3 days) postcoital cervicovaginal samples

Depending upon specific situations, some victims of sexual assault provide vaginal samples more than 36-48 h after the incident. We have tested the ability of commercial and in-house Y-STR systems to provide DNA profiles from extended interval (> or =3 days) postcoital samples. The commercial Y-STR systems tested included the AmpFlSTR Yfiler (Applied Biosystems), PowerPlex Y (Promega) and Y-PLEX 12 (Reliagene) products whereas the in-house systems comprised Multiplex I (MPI) and Multiplex B (MPB). Three donor couples were recruited for the study. Postcoital cervicovaginal swabs (x2) were recovered by each of the three females at specified intervals after sexual intercourse (3-7 days). Each time point sample was collected after a separate act of sexual intercourse and was preceded by a 7-day abstention period. As a negative control, a precoital swab was also recovered prior to coitus for each sampling and only data from postcoital samples that demonstrated a lack of male DNA in the associated precoital sample was used. A number of DNA profile enhancement strategies were employed including sampling by cervical brushing, nondifferential DNA extraction methodology, and post-PCR purification. Full Y-STR profiles from cervicovaginal samples recovered 3-4 days after intercourse were routinely obtained. Profiles were also obtainable 5-6 days postcoitus although by this stage partial profiles rather than full profiles were a more likely outcome. The DNA profiles from the sperm fraction of a differential lysis were superior to that obtained when a nondifferential method was employed in that the allelic signal intensities were generally higher and more balanced and exhibited less baseline noise. The incorporation of a simple post-PCR purification process significantly increased the ability to obtain Y-STR profiles, particularly from 5- to 6-day postcoital samples. Remarkably an 8 locus Y-STR profile was obtained from a 7-day postcoital sample, which is approaching the reported time limit for sperm detection in the cervix.     

Higher failures of amelogenin sex test in an Indian population group

The human sex test in forensic multiplexes is based on the amelogenin gene on both the X and Y chromosomes commonly used in sex genotyping. In this study of 338 male individuals in a Malaysian population comprising Malays, Chinese and Indians, using the AmpFlSTR Profiler Plus kit, the amelogenin test gave a significant proportion of null alleles in the Indian ethnic group (3.6% frequency) and 0.88% frequency in the Malay ethnic group due to a deletion of the gene on the Y chromosome. This sex test also failed in a forensic casework sample. Failure of the amelogenin test highlights the need for more reliable sex determination than is offered by the amelogenin locus in the Malay and Indian populations. The gender of the Indian-Malay amelogenin nulls was confirmed by the presence of three Y-STR alleles (DYS438, DYS390 and DYS439). For the Indian ethnic group, one of the Y-STR forms a stable haplotype with the amelogenin null. The amelogenin-deletion individuals also showed a null with a male-specific minisatellite MSY1, indicating that a very large deletion was involved that included the amelogenin and the MSY1 loci on the short arm of the Y chromosomes (Yp).     

Twelve short tandem repeat loci Y chromosome haplotypes: genetic analysis on populations residing in North America

A total of 2443 male individuals, previously typed for the 13 CODIS STR loci, distributed across the five North American population groups African American, Asian, Caucasian, Hispanic, and Native American were typed for the Y-STR loci DYS19, DYS385a/b, DYS389I/II, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438 and DYS439 using the PowerPlex Y System. All population samples were highly polymorphic for the 12 Y-STR loci with the marker DYS385a/b being the most polymorphic across all sample populations. The Native American population groups demonstrated the lowest genetic diversity, most notably at the DYS393 and DYS437 loci. Almost all of the 12-locus haplotypes observed in the sample populations were represented only once in the database. Haplotype diversities were greater than 99.6% for the African Americans, Caucasians, Hispanics, and Asians. The Native Americans had the lowest haplotype diversities (Apaches, 97.0%; Navajo, 98.1%). Population substructure effects were greater for Y-haplotypes, compared with that for the autosomal loci. For the apportionment of variance for the 12 Y-STRs, the within sample population variation was the largest component (>98% for each major population group and approximately 97% in Native Americans), and the variance component contributed by the major population groups was less than the individual component, but much greater than among sample populations within a major group (11.79% versus 1.02% for African Americans/Caucasians/Hispanics and 15.35% versus 1.25% for all five major populations). When each major population is analyzed individually, the R(ST) values were low but showed significant among group heterogeneity. In 692 confirmed father-son pairs, 14 mutation events were observed with the average rate of 1.57x10(-3)/locus/generation (a 95% confidence bound of 0.83x10(-3) to 2.69x10(-3)). Since the Y-STR loci reside on the non-recombining region of the Y chromosome, the counting method is one approach suggested for conveying an estimate of the rarity of the Y-haplotype. Because the Y-STR loci are not all in disequilibrium to the same extent, the counting method is a very conservative approach. The data also support that autosomal STR frequencies can be multiplied by the upper bound frequency estimate of a Y-haplotype in the individual population group or those pooled into major population groups (i.e., Caucasian, African American, Hispanic, and Asian). These analyses support use of the haplotype population data for estimating Y-STR profile frequencies for populations residing in North America.     

16 Y chromosomal STR haplotypes in Japanese

A total of 1079 Japanese males were typed for the following 16 Y chromosomal short tandem repeat (Y-STR) markers: DYS456, DYS389I, DYS390, DYS389II, DYS458, DYS19, DYS385, DYS393, DYS391, DYS439, DYS635, DYS392, Y GATA H4, DYS437, DYS438 and DYS448 using an AmpFlSTR(R) Yfiler PCR Amplification kit (Applied Biosystems). A total of 950 haplotypes for the 16 Y-STR markers were detected and, of these, 886 haplotypes were unique. The most frequent haplotype was found in 22 Japanese males. The haplotype diversity was 0.9992, indicating a high potential for differentiating between male individuals. There were 10 haplotypes with no allele detected at the DYS448 marker. Thus, the presence of such atypical haplotypes should be noted, when DNA typing results obtained from degraded DNA samples and/or DNA mixture samples from more than one male individual are being interpreted.     

7个Y-STR基因座单倍型及其法医学应用

目的调查7个Y-STR基因座单倍型及其法医学应用。方法利用二组复合扩增体系,(Ⅰ:DYS391、GATA-A4、GATA-A10和GATA-H4;Ⅱ:DYS439、DYS437和DYS434)检测7个Y染色体特异性的STR基因座,并用聚丙烯酰胺凝胶电泳和银染显色技术进行基因分型。结果在广东汉族372名无关男性个体中,二组7个基因座分别检出5、7、6、5和6、4、4个等位基因,共检出254种单倍型,其中201种为唯一的。单倍型基因多样性为0.9960。结论7个Y-STR基因座具有很高的识别能力,对建立Y染色体STR数据库,研究群体遗传学和进行法医学鉴定有重要意义。     

Development of a 24-plex Y chromosomal STR loci typing system

Y-chromosomal short tandem repeat (Y-STR) loci can play important roles in forensic casework and paternity testing. In our paper, 24-plex Y-STR typing system, which includes 3 loci (DYS635 and DYS385a/b) existed in current widely available commercial kits and 21 additional loci (DYS531, DYS630, DYS622, DYS552, DYS510, DYS449, DYS459a/b, DYS446, DYS443, DYS587, DYS527a/b, DYS460, Y-GATA-A10, DYS520, DYS557, DYS522, DYS481, DYS570, DYS444) was established with 5-dye fluorescence labeling. 200 unrelated Chinese Han males were successfully genotyped with the system and 198 haplotypes were observed. The gene diversity of each locus ranged from 0.55 (DYS531) to 0.96 (DYS385a/b), the haplotype of diversity was 0.9998 for these 24 Y-STR loci. The established 24-plex Y-STR typing system is proved to be stable and efficient in forensic DNA typing.