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N Morling

Publications and source records attributed to N Morling.

At least 19 recordsLinked to original sources
PubMed2006

DNA commission of the International Society of Forensic Genetics: Recommendations on the interpretation of mixtures.

The DNA commission of the International Society of Forensic Genetics (ISFG) was convened at the 21st congress of the International Society for Forensic Genetics held between 13 and 17 September in the Azores, Portugal. The purpose of the group was to agree on guidelines to encourage best practice that can be universally applied to assist with mixture interpretation. In addition the commission was tasked to provide guidance on low copy number (LCN) reporting. Our discussions have highlighted a significant need for continuing education and research into this area. We have attempted to present a consensus from experts but to be practical we do not claim to have conveyed a clear vision in every respect in this difficult subject. For this reason, we propose to allow a period of time for feedback and reflection by the scientific community. Then the DNA commission will meet again to consider further recommendations.

Alleles↗
PubMed2006

DNA Commission of the International Society of Forensic Genetics (ISFG): an update of the recommendations on the use of Y-STRs in forensic analysis.

The DNA Commission of the International Society of Forensic Genetics (ISFG) regularly publishes guidelines and recommendations concerning the application of DNA polymorphisms to the problems of human identification. A previous recommendation published in 2001 has already addressed Y-chromosome polymorphisms, with particular emphasis on short tandem repeats (STRs). Since then, the use of Y-STRs has become very popular, and a numerous new loci have been introduced. The current recommendations address important aspects to clarify problems regarding the nomenclature, the definition of loci and alleles, population genetics and reporting methods.

Alleles↗
PubMed2006

DNA Commission of the International Society of Forensic Genetics (ISFG): an update of the recommendations on the use of Y-STRs in forensic analysis.

The DNA Commission of the International Society of Forensic Genetics (ISFG) regularly publishes guidelines and recommendations concerning the application of DNA polymorphisms to the problems of human identification. A previous recommendation published in 2001 has already addressed Y-chromosome polymorphisms, with particular emphasis on short tandem repeats (STRs). Since then, the use of Y-STRs has become very popular, and numerous new loci have been introduced. The current recommendations address important aspects to clarify problems regarding the nomenclature, the definition of loci and alleles, population genetics and reporting methods

Alleles↗
PubMed2005

Analysis of artificially degraded DNA using STRs and SNPs--results of a collaborative European (EDNAP) exercise.

Recently, there has been much debate about what kinds of genetic markers should be implemented as new core loci that constitute national DNA databases. The choices lie between conventional STRs, ranging in size from 100 to 450 bp; mini-STRs, with amplicon sizes less than 200 bp; and single nucleotide polymorphisms (SNPs). There is general agreement by the European DNA Profiling Group (EDNAP) and the European Network of Forensic Science Institutes (ENFSI) that the reason to implement new markers is to increase the chance of amplifying highly degraded DNA rather than to increase the discriminating power of the current techniques. A collaborative study between nine European and US laboratories was organised under the auspices of EDNAP. Each laboratory was supplied with a SNP multiplex kit (Foren-SNPs) provided by the Forensic Science Service, two mini-STR kits provided by the National Institute of Standards and Technology (NIST) and a set of degraded DNA stains (blood and saliva). Laboratories tested all three multiplex kits, along with their own existing DNA profiling technique, on the same sets of degraded samples. Results were collated and analysed and, in general, mini-STR systems were shown to be the most effective. Accordingly, the EDNAP and ENFSI working groups have recommended that existing STR loci are reengineered to provide smaller amplicons, and the adoption of three new European core loci has been agreed.

Analysis of Variance↗
PubMed2005

Typing of multiple single-nucleotide polymorphisms using ribonuclease cleavage of DNA/RNA chimeric single-base extension primers and detection by MALDI-TOF mass spectrometry.

A novel single-base extension (SBE) assay using cleavable and noncleavable SBE primers in the same reaction mix is described. The cleavable SBE primers consisted of deoxyribonucleotides and one ribonucleotide (hereafter denoted chimeric primers), whereas the noncleavable SBE primers consisted of only deoxyribonucleotides (hereafter denoted standard primers). Biotin-labeled ddNTPs were used in the SBE reaction, and the SBE products were purified using the monomeric avidin triethylamine purification protocol, ensuring that only primers extended with a biotin-ddNTP in the 3'-end were isolated. A ribonuclease mix was developed to specifically cleave the chimeric primers, irrespective of the base of the ribonucleotide, whereas standard primers without a ribonucleotide were unaffected by the ribonuclease treatment. The SBE products were analyzed in linear mode using a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer. The cleaved SBE products were detected in the 2000-5500 m/z range, and the noncleaved SBE products were detected in the 5500-10 000 m/z range. The method was validated by typing 17 Y chromosome single-nucleotide polymorphisms in 100 males with a 17-plex SBE package containing 9 chimeric primers and 8 standard primers.

Base Sequence↗
PubMed2004

MALDI-TOF mass spectrometric detection of multiplex single base extended primers. A study of 17 y-chromosome single-nucleotide polymorphisms.

One of the most promising techniques for typing of multiple single-nucleotide polymorphism (SNP) is detection of single base extension primers (SBE) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). We present a new MALDI-TOF MS protocol for typing of multiple SNPs in a single reaction. Biotin-labeled ddNTPs were used in the SBE reaction and solid phase-bound monomeric avidin was used as capturing/purification scheme allowing the exclusive release of the SBE products under gentle conditions using 5% triethylamine. We dubbed this method monomeric avidin triethylamine purification. The biotin-labeled ddNTPs contained linkers with different masses ensuring a clear separation of the alleles even for SBE primers with a mass of 10 300 Da. Furthermore, only 25-350 fmol of SBE primers were necessary in order to obtain reproducible MALDI-TOF spectra. Similar signal intensities were obtained in the 5500-10 300 m/z mass range by increasing the concentration of the longer SBE primers in the reaction. To validate the technique, 17 Y-chromosome SNPs were analyzed in 200 males. The precision and accuracy of the mass determination were analyzed by parametric statistic, and the potential use of MALDI-TOF MS for SNP typing is discussed.

Alleles↗
PubMed2002

Sequencing strategy of mitochondrial HV1 and HV2 DNA with length heteroplasmy.

We describe a method to obtain reliable mitochondrial DNA (mtDNA) sequences downstream of the homopolymeric stretches with length heteroplasmy in the sequencing direction. The method is based on the use of junction primers that bind to a part of the homopolymeric stretch and the first 2-4 bases downstream of the homopolymeric region. This junction primer method gave clear and unambiguous results using samples from 21 individuals with length heteroplasmy in the hypervariable regions HV1, HV2 or both. The method is of special value for forensic casework, because sequencing of both strands of an mtDNA region is preferable in order to reduce ambiguities in sequence determination.

DNA, Mitochondrial↗
PubMed2001

Fluorescent SSCP of overlapping fragments (FSSCP-OF): a highly sensitive method for the screening of mitochondrial DNA variation.

The mtDNA analysis (mtDNA) is increasingly being demanded for forensic purposes due to the fact that many times the use of standard nuclear marker fails to analyze degraded samples (such as bones) and specially for the analysis of hair shafts (a common sample in the crime scene). However, analysis of mtDNA sequencing implies a great lab effort when a high number of samples must be analyzed. The present work introduces a novel and reliable method for the screening of mtDNA variation in the first and second hypervariables (HV1 and HV2) regions which we have denominated fluorescent single strand conformation polymorphism (SSCP) of overlapping fragments (FSSCP-OF). FSSCP-OF is based on the basic theory of SSCP analysis and combines two complementary strategies: the use of PCR amplified overlapping fragments and fluorescent detection technology. The overlap region contains a high percentage (50%) of the d-loop mtDNA variation and for this reason, the probability to detect a polymorphic position by SSCP analysis is clearly increased in comparison to conventional SSCP methods due to the fact that the same polymorphic position is usually placed in a different "relative" position in the two overlapped fragments. The use of multicolor fluorescent technology allows also the multiplex amplification of overlapping fragment and its subsequent analysis in an automatic sequencer. We have analyzed 50 samples of unrelated individuals through the FSSCP-OF technique and we have found that using this methodology the probability to distinguish two samples with different sequences is close to 100%. FSSCP-OF has other important advantages with respect to previous screening methods, such as the automation and standardization of the protocols, which is of special interest for the forensic routine.

Base Sequence↗
PubMed2001

DNA Commission of the International Society of Forensic Genetics: recommendations on forensic analysis using Y-chromosome STRs.

During the past few years, the DNA Commission of the International Society of Forensic Genetics has published a series of documents providing guidelines and recommendations concerning the application of DNA polymorphisms to the problems of human identification. This latest report addresses a relatively new area - namely, Y-chromosome polymorphisms, with particular emphasis on short tandem repeats (STRs). This report addresses nomenclature, use of allelic ladders, population genetics and reporting methods.

Alleles↗
PubMed2001

Results of a collaborative study of the EDNAP group regarding the reproducibility and robustness of the Y-chromosome STRs DYS19, DYS389 I and II, DYS390 and DYS393 in a PCR pentaplex format.

A collaborative exercise was carried out by the European DNA Profiling Group (EDNAP) in the frame work of the STADNAP program, i.e. standardization of DNA profiling in Europe, in order to evaluate the performance of a Y-chromosome STR pentaplex, which includes the loci DYS19, DYS389 I and II, DYS390 and DYS393 and to determine whether uniformity of results could be achieved among different European laboratories. Laboratories were asked to analyze the five Y-STRs using singleplex and multiplex conditions in three bloodstains and one mixed stain (95% female and 5% male). All the laboratories reported the same results even for the mixed stain included in the exercise. This demonstrates the reproducibility and robustness of Y-chromosome STR typing even with multiplex formats and proves the usefulness of Y-STR systems for analyzing mixed stains with a male component.A total of 930 male samples from 10 different populations from Europe were also analysed for all the loci included in the pentaplex. Eight of these ten populations also included haplotype data. As for single gene analysis, haplotype diversity was higher in Germany and Italy and lower in Western European countries and Finland. Pairwise haplotype analysis shows the Finnish departure from the rest of the populations and a relatively homogeneity in the other European populations with F(ST) estimates lower than 0.05.UPGMA analysis shows an association of Western European population (Ireland, UK, Portugal and Galicia) on the one hand and central European populations on the other.

Blood Stains↗
PubMed2001

A report of the 1997, 1998 and 1999 Paternity Testing Workshops of the English Speaking Working Group of the International Society for Forensic Genetics.

We present the results of the 1997, 1998 and 1999 Paternity Testing Workshops of the English Speaking Working Group of the International Society for Forensic Genetics. The numbers of participating laboratories were 24 (1997), 31 (1998) and 32 (1999). In 1997, all laboratories drew the correct conclusion that the alleged father was the biological father of the child. In 1998, the alleged father was the biological brother of the child and all laboratories excluded him. The scenario in 1999 was a deficiency case consisting of mother, child and the parents of the alleged father and all but one laboratory drew the correct conclusion.The percentage of laboratories routinely performing variable number of tandem repeat (VNTR) investigations using single locus probes (SLPs) and restriction fragment length polymorphism (RFLP) decreased from 83% in 1997 to 66% in 1999. In the three workshops, more than 90% of the laboratories used polymerase chain reaction (PCR) based systems. In 1999, 80% of the laboratories performing PCR, used commercially available short tandem repeat (STR) kits. Other commonly used systems were HLA and PolyMarker investigated with PCR. Conventional systems and RFLP investigations of VNTRs with multi loci probes (MLPs) were used routinely by approximately 20% of the participating laboratories. All laboratories submitting results in the three workshops used RFLP-based VNTRs or/and PCR based VNTRs/STRs. Inter-laboratory comparisons of the results showed a very high concordance. The overall coefficients of variation between the laboratories of the results of RFLP typing of the commonly used VNTRs D2S44, D7S21, D7S22 and D12S11 were 1.2-1.3%. Consistent results were obtained in the great majority of the systems investigated by PCR and typing errors counted for less than 0.3% of the PCR based results.

Accreditation↗
PubMed2001

DNA commission of the International Society of Forensic Genetics: recommendations on forensic analysis using Y-chromosome STRs.

During the past few years the DNA commission of the International Society of Forensic Genetics has published a series of documents providing guidelines and recommendations concerning the application of DNA polymorphisms to the problems of human identification. This latest report addresses a relatively new area, namely Y-chromosome polymorphisms, with particular emphasis on short tandem repeats (STRs). This report addresses nomenclature, use of allelic ladders, population genetics and reporting methods.

Alleles↗