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At least 991 records · Page 55Linked to original sources
PubMed2006

DNA sequencing and multiplex STR analysis on plastic microfluidic devices.

The ability of plastic microfluidic devices with separation channel lengths of 6, 10 or 18 cm to perform high-quality and high-performance ssDNA analysis was evaluated. Specifically, four-color DNA sequencing separation of a terminator sequencing standard using replaceable, urea-denaturing linear polyacrylamide (LPA) solution as a sieving matrix, yielded read lengths of 410 bases in 15 min with base calling accuracy of 99.2% on a 6-cm device, and 640 bases in 35 min with accuracy of 98.0% on a 18-cm device. A two-color sizing analysis of four-locus (CSF1PO, TPOX, TH01, vWA) short tandem repeats (STRs) allelic ladder on a 10-cm device indicated a mean SD of +/- 0.08 base pairs (bp) between runs, and single bp resolution of spiked TH01 allele 9.3 (198 bp) from TH01 allele 10 (199 bp) of the CTTv ladder with R = 0.81. A four-color multiplex sizing analysis of three different AmpFlSTR allelic ladders consisting of nine loci (D3S1358, vWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317, D7S820) and gender alleles (Amelogenin) on a 10-cm device had a mean SD of +/- 0.15 bp between runs for sizing three loci, i.e., FGA, D18S51 and D3S818; alleles differing by 2 bp in size were resolved with resolutions close to baseline. This work demonstrates that plastic microfluidic devices are capable of quality sequencing and STR sizing comparable to that of glass devices of similar separation lengths.

DNA, Single-Stranded↗
PubMed2001

Haplotype analysis and age estimation of the 113insR CDKN2A founder mutation in Swedish melanoma families.

Germline mutations in the CDKN2A tumor suppressor gene located on 9p21 have been linked to development of melanomas in some families. A germline 3-bp insertion in exon 2 of CDKN2A, leading to an extra arginine at codon 113 (113insR), has been identified in 17 Swedish melanoma families. Analysis of 10 microsatellite markers, spanning approximately 1 Mbp in the 9p21 region, showed that all families share a common allele for at least one of the markers closest to the CDKN2A gene, suggesting that the 113insR mutation is an ancestral founder mutation. Differences in the segregating haplotypes, due to meiotic recombinations and/or mutations in the short-tandem-repeat markers, were analyzed further to estimate the age of the mutation. Statistical analysis using a maximum likelihood approach indicated that the mutation arose 98 generations (90% confidence interval: 52-167 generations), or approximately 2,000 years, ago. Thus, 113insR would be expected to have a more widespread geographic distribution in European and North American regions with ancestral connections to Sweden. Alternatively, CDKN2A may lie in a recombination hot spot region, as suggested by the many meiotic recombinations in this narrow approximately 1-cM region on 9p21.

Alleles↗
PubMed2001

Smallest region of overlapping deletion in 1p36 in human neuroblastoma: a 1 Mbp cosmid and PAC contig.

In human neuroblastomas, the distal portion of 1p is frequently deleted, as if one or more tumor suppressor genes from this region were involved in neuroblastoma tumorigenesis. Earlier studies had identified a smallest region of overlapping deletion (SRO) spanning approximately 23 cM between the most distally retained D1S80 and by the proximally retained D1S244. In pursuit of generating a refined delineation of the minimally deleted region, we have analyzed 49 neuroblastomas of different stages for loss of heterozygosity (LOH) from 1pter to 1p35 by employing 26 simple sequence length polymorphisms. Fifteen of the 49 tumors (31%) had LOH; homozygous deletion was not detected. Seven tumors had LOH at all informative loci analyzed, and eight tumors showed a terminal or an interstitial allelic loss of 1p. One small terminal and one interstitial deletion defined a new 1.7 cM SRO, approximately 1 Mbp in physical length, deleted in all tumors between the retained D1S2731 (distal) and D1S2666 (proximal). To determine the genomic complexity of the deleted region shared among tumors, we assembled a physical map of the I Mbp SRO consisting predominantly of bacteriophage P1-derived artificial chromosome (PAC) clones. A total of 55 sequence-tagged site (STS) markers (23 published STSs and short tandem repeats and 32 newly identified STSs from the insert ends of PACs and cosmids) were assembled in a contig, resulting in a sequence-ready physical map with approximately one STS per 20 Kbp. Twelve genes (41BB, CD30, DFFA, DJ1, DR3, FRAP, HKR3, MASP2, MTHFR, RIZ, TNR2, TP73) previously mapped to 1p36 are localized outside this SRO. On the basis of this study, they would be excluded as candidate genes for neuroblastoma tumorigenesis. Ten expressed sequence tags were integrated in the contig, of which five are located outside the SRO. The other five from within the SRO may provide an entrance point for the cloning of candidate genes for neuroblastoma.

Bacteriophage P1↗
PubMed2004

Combined association and linkage analysis applied to the APOE locus.

Combined association and linkage analysis is a powerful tool for pinpointing functional quantitative traits (QTLs) responsible for regions of significant linkage identified in genome-wide scans. We applied this technique to apoE plasma levels and the APOEepsilon2/epsilon3/epsilon4 polymorphism in two Dutch twin cohorts of different age ranges. Across chromosome 19, short tandem repeats and the APOEepsilon2/epsilon3/epsilon4 polymorphism were genotyped in adolescent (aged 13-22 years) and adult (aged 34-62 years) Dutch twins. In both samples, evidence for indicative linkage with plasma apoE levels was found (maximum LOD score (MLS)=0.8, MLS=2.5, respectively) at 19q13.32. These linkage regions included the APOE locus. As expected, the APOEepsilon2/epsilon3/epsilon4 polymorphism was strongly associated with apoE plasma levels in both samples. An extension of the between/within families association test developed by Fulker et al. ([1999] Am. J. Hum. Genet. 64:259-267) showed that these associations were not due to population stratification. The combined association and linkage analyses revealed that the association of the APOEepsilon2/epsilon3/epsilon4 polymorphism with apoE plasma levels completely explained the linkage in the adolescent twins and partly in the adult twins.

Adolescent↗
PubMed2005

Association mapping: methodologies, strategies, and issues.

Recent advances in molecular genetic technology allow for detailed characterization of genetic variation and easy cost-efficient accumulation of such data, even for large human samples. One such advance that presents incredible opportunities for identifying associations between genetic polymorphisms and disease-related phenotypes is the ability to quickly type a large number of single-nucleotide polymorphisms (SNPs). Contributors to Group 10 of Genetic Analysis Workshop 14 explored the potential of SNP genotypes for the association mapping of disease-related genes in family-based studies. Using both real data involving alcoholism susceptibility, made available by the Collaborative Study on the Genetics of Alcoholism (COGA), and simulated data involving personality-disorder susceptibility, group members investigated specific methodological issues involved in association mapping, such as multiple testing, single SNPs vs. combinations and haplotypes, and the effect of linkage disequilibrium on SNP-based linkage; evaluated existing methodologies for association mapping using SNPs, short-tandem repeats (STRs), or a combination of the two; and introduced new or modified association-mapping methods, including a gamma random effects (GRE) model and the quantitative trait linkage disequilibrium (QTLD) test. These papers are unified by the application of association-based methods to analyze SNPs, microsatellite markers, or both, to identify chromosomal regions harboring genes that contribute to quantitative endophenotype variation, and thus to disease risk. Their diversity attests to the breadth and flexibility of association-mapping approaches to the genetics of complex disease.

Alcoholism↗
PubMed1999

Multiple genetic alterations, 4q28, a new suppressor region, and potential gender differences in human hepatocellular carcinoma.

Primary hepatocellular carcinomas (HCCs) of different etiologies were studied to determine the rate of alteration of several genetic regions previously associated with the HCC phenotype. The focus of our study was to identify the frequency of genetic alterations within individual HCCs and their distribution among male and female cases. Genetic differences were evaluated between DNA isolated from tumor (T) and corresponding non-tumor (N) tissue using short tandem repeat (STR)-microsatellites and restriction fragment length polymorphism (RFLP) analyses. Twenty-eight HCC cases were studied with polymorphic markers from different parts of the genome. Three or more loci were identified with genetic alterations from 28 loci tested in 63% of HCC cases. The highest frequency of alteration occurred in the chromosome regions 1p36, 13q14, 17p13, and the 4q28 region identified in HCCs for the first time. High loss of heterozygosity (LOH) in 1p36, 4q28, 13q14, and 17p13 regions indicates important HCC suppressors within the regions. The study documents no association between cause and specific genetic change or their frequency in HCCs analyzed. The data document a significant gender distortion for genetic alteration in chromosome 13q14 and 17p13 regions and a concordant gender alteration rate in the 1p36 and 4q28 regions. An overall higher frequency of genetic alterations was identified in male cases. Future study with an extended number of HCC cases should substantiate the frequency of alteration between genders and identify tentative suppressors in the 1p36 and 4q28 regions.

Adult↗
PubMed2002

Determining sequence length or content in zero, one, and two dimensions.

High-throughput assays are essential for the practical application of mutation detection in medicine and research. Moreover, such assays should produce informative data of high quality that have a low-error rate and a low cost. Unfortunately, this is not currently the case. Instead, we typically witness legions of people reviewing imperfect data at astronomical expense yielding uncertain results. To address this problem, for the past decade we have been developing methods that exploit the inherent quantitative nature of DNA experiments. By generating high-quality data, careful DNA-signal quantification permits robust analysis for determining true alleles and certainty measures. We will explore several assays and methods. In a one-dimensional readout, short tandem repeat (STR) data display interesting artifacts. Even with high-quality data, PCR artifacts such as stutter and relative amplification can confound correct or automated scoring. However, by appropriate mathematical analysis, these artifacts can be essentially removed from the data. The result is fully automated data scoring, quality assessment, and new types of DNA analysis. These approaches enable the accurate analysis of pooled DNA samples, for both genetic and forensic applications. On a two-dimensional surface (comprised of zero-dimensional spots) one can perform assays of extremely high-throughput at low cost. The question is how to determine DNA sequence length or content from nonelectrophoretic intensity data. Here again, mathematical analysis of highly quantitative data provides a solution. We will discuss new lab assays that can produce data containing such information; mathematical transformation then determines DNA length or content.

Artifacts↗
PubMed2003

Independent mutational events are rare in the ATM gene: haplotype prescreening enhances mutation detection rate.

Mutations in the ATM gene are responsible for the autosomal recessive disorder ataxia-telangiectasia (A-T). Many different mutations have been identified using various techniques, with detection efficiencies ranging from 57 to 85%. In this study, we employed short tandem repeat (STR) haplotypes to enhance mutation identification in 55 unrelated A-T families of Iberian origin (20 Spanish, 17 Brazilian, and 18 Hispanic-American); we were able to identify 95% of the expected mutations. Allelic sizes were standardized based on a reference sample (CEPH 1347-2). Subsequent mutation screening was performed by PTT, SSCP, and DHPLC, and abnormal regions were sequenced. Many STR haplotypes were found within each population and six haplotypes were observed across several of these populations. Single nucleotide polymorphism (SNP) haplotypes further suggested that most of these common mutations are ancestrally related, and not hot spots. However, two mutations (8977C>T and 8264_8268delATAAG) may indeed be recurring mutational events. Common haplotypes were present in 13 of 20 Spanish A-T families (65%), in 11 of 17 Brazilian A-T families (65%), and, in contrast, in only eight of 18 Hispanic-American families (44%). Three mutations were identified that would be missed by conventional screening strategies. In all, 62 different mutations (28 not previously reported) were identified and their associated haplotypes defined, thereby establishing a new database for Iberian A-T families, and extending the spectrum of worldwide ATM mutations.

Ataxia Telangiectasia↗
PubMed2001

Matroshka and ectopic polymorphisms: Two new classes of DNA sequence variation identified at the Van der Woude syndrome locus on 1q32-q41.

Van der Woude syndrome (VWS) is an orofacial clefting disorder with an autosomal dominant pattern of inheritance. In our efforts to clone the VWS gene, 900 kb of genomic sequence from the VWS candidate region at chromosome 1q32-q41 was analyzed for new DNA sequence variants. We observed that in clone CTA-321i20 a 7922 bp sequence is absent relative to the sequence present in PAC clone RP4-782d21 at positions 1669-9590, suggesting the presence of a deletion/insertion (del/ins) polymorphism. Embedded in this 7922 bp region was a TTCC short tandem repeat (STR). Genotype analysis showed that both the internal STR and the (del/ins) mutation were true polymorphisms. This is a novel example of intraallelic variation, a polymorphism within a polymorphism, and we suggest that it be termed a "Matroshka" polymorphism. Further genetic and DNA sequence analysis indicated that the ancestral state of the 1669-9590 del/ins polymorphism was the insertion allele and that the original deletion mutation probably occurred only once. A second class of novel DNA sequence variation was discovered on chromosome 5 that shared a 328 bp identical sequence with this region on chromosome 1. A single nucleotide polymorphism (SNP) was detected by SSCP using a pair of primers derived from the chromosome 1 sequence. Surprisingly, these primers also amplified the identical locus on chromosome 5, and the SNP was only located on chromosome 5. Since the probe unexpectedly detected alleles from another locus, we suggest that this type of sequence variant be termed an "ectopic" polymorphism. These two novel classes of DNA sequence polymorphisms have the potential to confound genetic and DNA sequence analysis and may also contribute to variation in disease phenotypes.

Alleles↗
PubMed1993

Genomic instability occurs in colorectal carcinomas but not in adenomas.

Genomic instability, as demonstrated by the presence of additional alleles at short tandemly repeated (STR) loci, has recently been observed in colorectal tumours from individuals with hereditary nonpolyposis colorectal cancer (HNPCC), and in some sporadic tumours. These neoplasms have been called replication error positive (RER+). In this study, we confirm the presence of genomic instability in a proportion of unselected colorectal carcinomas but find no evidence of instability in adenomas. We further report replication errors in a tetranucleotide sequence, and in STRs within two tumour suppressor genes. 108 colorectal adenocarcinomas and 46 adenomas were analysed for the presence of variant bands at 4-15 microsatellite markers. Seven (6.5%) of carcinomas were RER+, four of which originated from the proximal colon. Analysis of the adenomas and of matched adenoma-carcinoma and carcinoma-metastatic samples from four patients suggests that the replication errors may occur during the development of carcinomas but are rare in adenomas.

Adenocarcinoma↗
PubMed2005

Comparison of yield and genotyping performance of multiple displacement amplification and OmniPlex whole genome amplified DNA generated from multiple DNA sources.

The promise of whole genome amplification (WGA) is that genomic DNA (gDNA) quantity will not limit molecular genetic analyses. Multiple displacement amplification (MDA) and the OmniPlex PCR-based WGA protocols were evaluated using 4 and 5 ng of input gDNA from 60 gDNA samples from three tissue sources (mouthwash, buffy coat, and lymphoblast). WGA DNA (wgaDNA) yield and genotyping performance were evaluated using genotypes determined from gDNA and wgaDNA using the AmpFlSTR Identifiler assay and N = 49 TaqMan SNP assays. Short tandem repeat (STR) and SNP genotyping completion and concordance rates were significantly reduced with wgaDNA from all WGA methods compared with gDNA. OmniPlex wgaDNA exhibited a greater reduction in genotyping performance than MDA wgaDNA. Reduced wgaDNA genotyping performance was due to allelic (all protocols) and locus (OmniPlex) amplification bias leading to heterozygote and locus dropout, respectively, and %GC sequence content (%GC) was significantly correlated with TaqMan assay performance. Lymphoblast wgaDNA exhibited higher yield (OmniPlex), buffy coat wgaDNA exhibited higher STR genotyping completion (MDA), whereas mouthwash wgaDNA exhibited higher SNP genotyping discordance (MDA). Genotyping of wgaDNA generated from < or = 5 ng gDNA, e.g., from archaeological, forensic, prenatal diagnostic, or pathology samples, may require additional genotyping validation with gDNA and/or more sophisticated analysis of genotypes incorporating observed reductions in genotyping performance.

Adult↗
PubMedDate not supplied

Sperm mitochondrial mutations as a cause of low sperm motility.

We report the unique case of a 28-year-old man who, in spite of having a varicocele and a sperm concentration of 5 million/mL, of which 10% were motile and 20% had normal forms (oligoasthenoteratozoospermia [OAT]), was fertile. This was confirmed by paternity testing using 16 autosomal and 6 Y-chromosomal short tandem repeat (STR) loci. An analysis of mitochondrial genes that included cytochrome oxidase I (COI), cytochrome oxidase II (COII), adenosine triphosphate synthase6 (ATPase6), ATPase8, transfer ribonucleic acid (tRNA) serine I, tRNA lysine, and NADH dehydrogenase3 (ND3) revealed, for the first time, 9 missense and 27 silent mutations in the sperm's mitochondrial DNA (mtDNA) but not in the DNA from the blood cells. There was a 2-nucleotide deletion in the mitochondrial COII genes, introducing a stop codon, which might be responsible for low sperm motility.

Adult↗
PubMedDate not supplied

Analysis of nucleic acids by on-line liquid chromatography-mass spectrometry.

The numerous problems posed by modern biochemistry, biology, and medicine, as well as the growing significance of genetic engineering require the application of fast and reliable methods of utmost sensitivity and selectivity for the analysis of nucleic acids. High-performance liquid chromatography (HPLC) and mass spectrometry (MS) represent established analytical techniques for the characterization and structural elucidation of single- and double-stranded nucleic acids, ranging in size from a few nucleotides to several thousand base pairs. Although both techniques are independently applicable for nucleic acid analysis, the on-line hyphenation significantly enhances their potential for the robust and fully automable routine analysis of minute amounts of biological samples. Among the various chromatographic and mass spectrometric modes available in principle, ion-pair reversed-phase HPLC and electrospray ionization mass spectrometry (ESI-MS) have been shown to be the most suitable for the direct interfacing of liquid chromatography (LC) and MS. Instrumental setup, as well as chromatographic and mass spectrometric experimental conditions, need to be carefully selected in order to maximize the performance of the hyphenated analytical system. Applications of HPLC-ESI-MS include the characterization of oligodeoxynucleotides synthesized by solid-phase synthesis, the analysis of antisense oligodeoxynucleotides, oligonucleotide metabolites, and DNA adducts, the analysis of genomic segments specifically amplified by the polymerase chain reaction (PCR), the characterization of ribonucleic acids, the sizing of double-stranded DNA restriction fragments, the genotyping of short tandem repeats (STRs) and single nucleotide polymorphisms (SNPs), the detection of mutations in nucleic acid sequences, and the sequencing of nucleic acids.

Animals↗
PubMed2005

Frequent sequence variation at the ETM2 locus and its association with sporadic essential tremor in Korea.

Essential tremor (ET) is the most common but a complex neurological movement disorder. ET usually affects hands, but it may also affect head, neck, face, jaw, tongue, voice, trunk and, rarely, legs and feet. Although two susceptibility loci were identified on chromosome 2p24 (ETM2) and 3q13 (ETM1 or FET1), the exact transcript(s) has not been cloned. We analyzed unrelated Korean individuals with ET for a genetic association with three reported polymorphic loci (STS-etm1240, STS-etm1231, and STS-etm1234) in a candidate region on chromosome 2p24.1. We investigated sequence polymorphisms at these three loci in 30 ET patients and 30 controls using polymerase chain reaction (PCR) amplification followed by sequence analysis. Eight different sequence variants (5 at etm1234, 2 at etm1240, and 1 at etm1231) were detected from 7 patients. Of interest, sequence variants were found only in classic ET patients but not in nonclassic ET patients and healthy individuals. Additionally, we also observed that a decrease in the number of short tandem repeats within etm1234 locus is more frequent in ET patients compared to controls. Our data thus support that ET development would be linked with the ETM2 locus and will facilitate the search for the ETM2 gene transcript.

Aged↗
PubMed1995

Loss of heterozygosity in ductal carcinoma in situ of the breast.

Loss of heterozygosity (LOH) at loci reported to show allele loss in invasive breast cancers was examined in ductal in situ carcinomas of the breast using polymorphic short tandem repeats and the polymerase chain reaction (PCR). LOH was detected at all loci examined in at least 11 per cent of the samples examined. The proportion of cases of in situ carcinoma showing LOH at these loci was similar to that previously reported in invasive cancers. Cases of pure in situ cancer without an invasive component exhibited an overall lower frequency of allele loss. LOH at more than one locus was observed in some intraductal cancers. In a small number of cases, LOH was present in the invasive but not in the intraductal component of the tumour, suggesting that mutation at the locus concerned was associated with development of invasive behaviour.

Breast Neoplasms↗
PubMed2005

Prenatal diagnosis of monosomy 4p14-->pter and trisomy 11q25-->qter: clinical presentations and outcomes.

We present the case of a pregnant woman with low free beta-HCG in maternal serum Down syndrome screening that led to prenatal diagnosis of a fetus with 46,XY,der(4)t(4;11)(p14; q25). This chromosomal aneuploidy resulted from unbalanced segregation of a paternal balanced translocation, t(4;11)(p14;q25). Prenatal ultrasound revealed intrauterine growth restriction, cleft lip and palate, a thick nuchal fold, a single umbilical artery, and pyelectasis. Array-based comparative genomic hybridization and short tandem repeat markers further located the exact breakpoint of translocation. The woman had her pregnancy terminated at 23 weeks of gestational age. The proband had general appearance of Wolf-Hirschhorn syndrome and some unique findings, including single umbilical artery, severe immunoglobulin deficiency, scalp defect, and underlying bony defect. Our case underscores the importance of fetal karyotyping when low maternal serum free beta-HCG is found. It also adds information on the fetal presentations of monosomy 4p14-->pter and trisomy 11q25-->qter.

Abnormalities, Multiple↗
PubMed2006

The consanguinity effect on QF-PCR diagnosis of autosomal anomalies.

OBJECTIVES: Quantitative Fluorescent PCR (QF-PCR) is a simpler and faster method of detecting common chromosomal abnormalities when compared to cytogenetic analysis. The aim of our study is to investigate the applicability of this methodology in a population where consanguineous marriages are common and to estimate the heterozygous frequency of the PCR markers used. METHODS: Four hundred and twenty-three DNA samples were extracted from uncultured amniocytes and amplified with 18 short tandem repeats (STR) markers specific to chromosomes 13, 18 and 21. Amplification products were analyzed using the GeneScan software. RESULTS: QF-PCR correctly identified all the numerical abnormalities related to chromosomes 13, 18 and 21. A total of 24 autosomal trisomies (5.7%) were detected. The markers D21S1432 and D21S11 were the most consistent in providing unequivocal positive results for chromosome 21 and the heterozygosity percentages of the markers used were lower than the values reported in Western populations. CONCLUSION: QF-PCR is reliable for the prenatal diagnosis of numerical anomalies of the chromosomes 13, 18 and 21 in our study population. The absence of STR heterozygosity data from Lebanon and surrounding countries makes our study very useful for the development of a reliable QF-PCR trisomy detection test.

Adult↗
PubMed2006

A prospective analysis of cell-free fetal DNA concentration in maternal plasma as an indicator for adverse pregnancy outcome.

OBJECTIVES: To evaluate whether cell-free fetal (cff) DNA in maternal plasma during the second trimester is a marker for developing pregnancy-associated complications. Two PCR techniques for the detection and quantitation of fetal DNA were compared. METHODS: Plasma samples were prospectively collected from 84 pregnant women carrying male fetuses before amniocentesis (14-29 weeks). We later recorded 26 pregnancies with complicated outcomes, including five cases of fetal chromosomal abnormalities. For statistical analysis, two overlapping subgroups A and B were made. Each group was separately compared for total and fetal DNA with a corresponding group considered normal using Wilcoxon rank sum test. Male fetal DNA concentration in maternal plasma was quantified using real-time quantitative polymerase chain reaction (PCR) of SRY sequences. The samples were also analyzed by quantitative fluorescent PCR (QF-PCR) using highly polymorphic short tandem repeat DNA sequences (STRs), and the percentage of relative fetal allele concentration in maternal alleles was calculated and compared to the fetal/total DNA ratio obtained by real-time PCR. RESULTS: Quantities of total and fetal circulating DNA were significantly correlated (r(2) = 0.44, P < 0.0001) with a median total DNA concentration of 522 GE/mL (range 51-3047) and a median fetal DNA concentration of 8 GE/mL (range 0-879). Neither level was correlated with gestational age in pregnancies with normal (r(2) = -0.05; P = 0.66, and r(2) = 0.02; P = 0.88, respectively) and abnormal (r(2) = 0.45; P = 0.17, and r(2) = 0.11; P = 0.76, respectively) outcomes. Although both total and fetal DNA levels were always higher in women carrying pregnancies with chromosomal aberrations or having other pregnancy complications (P-values range from 0.028 to 0.267), these differences reached statistical significance only for total DNA levels between the group A and corresponding normal pregnancies (P = 0.028). The correlation between the fetal/total DNA ratio obtained by real-time PCR and the percentage of relative fetal allele concentration in maternal alleles obtained by QF-PCR was not found to be statistically significant (r(2) = 0.04; P = 0.76). CONCLUSION: Our results confirm the clinical value of fetal DNA measurement in maternal plasma during the second trimester as a supplement for the diagnosis of aneuploidies. Its use as a screening instrument for complications that develop later in pregnancy seems to be limited but needs further investigation. Although the QF-PCR assay has the advantage of being applicable to both female and male fetuses, this approach cannot be used for quantitation of cff DNA in maternal plasma samples.

Alleles↗