Minute Quantities Of DNA Research Articles

Comparison between various DNA sterilization procedures applied in forensic analysis

BackgroundThe advanced sensitive STR kits applied in forensic DNA typing techniques can cause challenging issues when evidence samples are contaminated with minute quantities of DNA from another source such as forensic analysts or crime scene examiners.ResultsIn this study, laboratory air and surfaces, gloves, tools, and equipment were evaluated as potential sources of contaminating DNA. Different sterilization methods were tested for their ability to efficiently eliminate DNA in a sample. Inactivation methods included 10% bleach, ethanol, UV light, and DNA-ExitusPlus IF. Exposure to the different inactivation protocols for varying periods of time was performed in two lab settings: low template DNA and DNA database labs. Surfaces were swabbed and any adhering DNA was quantified using HID real-time PCR. Results were detected using HID Real-Time PCR Analysis Software v1.2 and GeneMapper ID-X Software v1.4.ConclusionsIt was concluded that most of the DNA decontamination methods are not suitable for highly sensitive and precision STR kits such as GlobalFiler PCR Amplification Kit. The most suitable tested method was using DNA-ExitusPlus IF with the incubation time increased from 10 to 15 min.

An Effective and Viable DNA Extraction Protocol for FFPE Tissues and its Effect on Downstream Molecular Application

Archival Formalin-Fixed Paraffin-Embedded (FFPE) tissues are a readily available source of DNA for retrospective studies including genetic predisposition. FFPE tissues present significant challenges for extraction of pure genomic DNA in adequate amounts due to the harsh fixation conditions and long-term storage associated with samples. The aim of the study is to propose a simple, in-expensive, viable protocol for the extraction of DNA from FFPE tissues and to optimize the same for the detection of 3’UTR miRNA binding site polymorphism in ADAMTS1 gene in colorectal cancer tissues and normal colonic mucosa archival tissues using Sanger sequencing and TaqMan SNP genotyping assay. Five different DNA extraction methods were compared and analyzed. NanoDrop quantification demonstrated that out of the various methods tested, highest quantity and pure DNA was obtained from Modified non heating extraction. When we further applied this method for colorectal cancer tissues and normal colonic mucosa archival tissues the NanoDrop readout indicated that the DNA was intact and pure. Intra samples comparison over a time period of 6 months revealed that the DNA was intact. The samples isolated with Modified non heating extraction were found suitable for downstream processes such as Sanger sequencing and TaqMan SNP genotyping assay. This cost effective and non-arduous protocol can successfully extract even minute quantities of DNA from FFPE tissues and facilitate the downstream molecular analysis of a large number of archival specimens for retrospective studies.

Methylation-Specific Multiplex Ligation-Dependent Probe Amplification (MS-MLPA).

This chapter describes a method for the rapid assessment of promoter hypermethylation levels or methylation of imprinted regions in human genomic DNA extracted from various sources using methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA). Multiplex ligation-dependent probe amplification (MLPA) is a powerful and easy-to-perform PCR-based technique that can identify gains, amplifications, losses, deletions, methylation and mutations of up to 55 targets in a single reaction, while requiring only minute quantities of DNA (about 50ng) extracted from blood, fresh frozen or formalin-fixed paraffin-embedded materials. Methylation-specific MLPA (MS-MLPA) is a variant of MLPA, which does not require sodium bisulfite conversion of unmethylated cytosine residues, but instead makes use of the methylation-sensitive endonuclease HhaI. MS-MLPA probes are designed to contain a HhaI recognition site (GCGC) and thus target one CpG dinucleotide within a CpG island. If the HhaI recognition site is not methylated, HhaI will cut the probe-sample DNA hybrid and no PCR product will be formed. If the target DNA is methylated, HhaI is not able to cut, and the fragment will be amplified during subsequent PCR. For data analysis, MS-MLPA peak patterns of the HhaI-treated and -untreated reactions are compared, leading to calculation of a methylation percentage. The methylation profile of a test sample is assessed by comparing the probe methylation percentages obtained on the test sample to the percentages of the reference samples. MS-MLPA can be combined with copy number and point mutation detection in the same reaction.

A method for positive forensic identification of samples from extremely low-coverage sequence data.

BackgroundDetermining whether two DNA samples originate from the same individual is difficult when the amount of retrievable DNA is limited. This is often the case for ancient, historic, and forensic samples. The most widely used approaches rely on amplification of a defined panel of multi-allelic markers and comparison to similar data from other samples. When the amount retrievable DNA is low these approaches fail.ResultsWe describe a new method for assessing whether shotgun DNA sequence data from two samples are consistent with originating from the same or different individuals. Our approach makes use of the large catalogs of single nucleotide polymorphism (SNP) markers to maximize the chances of observing potentially discriminating alleles. We further reduce the amount of data required by taking advantage of patterns of linkage disequilibrium modeled by a reference panel of haplotypes to indirectly compare observations at pairs of linked SNPs. Using both coalescent simulations and real sequencing data from modern and ancient sources, we show that this approach is robust with respect to the reference panel and has power to detect positive identity from DNA libraries with less than 1 % random and non-overlapping genome coverage in each sample.ConclusionWe present a powerful new approach that can determine whether DNA from two samples originated from the same individual even when only minute quantities of DNA are recoverable from each.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2241-6) contains supplementary material, which is available to authorized users.

Comparative study of STR loci for typing old skeletal remains with modified protocols of AmpFlSTR Identifiler and AmpFlSTR MiniFiler STR Kits

This study highlights a comparative study of short tandem repeat (STR) loci with modified protocols of AmpFlSTR Identifiler and AmpFlSTR MiniFiler STR Kits for typing 27 old skeletal remains collected from 100–1000-year-old mass graves in Pakistan. DNA profiles were obtained from minute quantities of DNA (even from ≤ 10 pg/μL) with modified protocols of these kits, which is a significant achievement in this study. Consensus profiles were produced for each bone sample. A comparison was carried out between Identifiler and Minifiler successfully genotyped STR loci. Full concordance was perceived in 97.33% (146/150) of the compared STR loci, while discordant STR loci were 2.67% (4/150) of the total successfully genotyped STR loci due to either or both allele drop-out or drop-in. Finally, it was observed that the AmpFlSTR MiniFiler kit promoted the recovery of locus/alleles that failed to type with the AmpFlSTR Identifiler kit and more informative DNA profiles were obtained from old skeletal remains with the AmpFlSTR MiniFiler STR kit compared with the AmpFlSTR Identifiler STR kit.

Deciphering the Epigenetic Code: An Overview of DNA Methylation Analysis Methods

Methylation of cytosine in DNA is linked with gene regulation, and this has profound implications in development, normal biology, and disease conditions in many eukaryotic organisms. A wide range of methods and approaches exist for its identification, quantification, and mapping within the genome. While the earliest approaches were nonspecific and were at best useful for quantification of total methylated cytosines in the chunk of DNA, this field has seen considerable progress and development over the past decades. Methods for DNA methylation analysis differ in their coverage and sensitivity, and the method of choice depends on the intended application and desired level of information. Potential results include global methyl cytosine content, degree of methylation at specific loci, or genome-wide methylation maps. Introduction of more advanced approaches to DNA methylation analysis, such as microarray platforms and massively parallel sequencing, has brought us closer to unveiling the whole methylome. Sensitive quantification of DNA methylation from degraded and minute quantities of DNA and high-throughput DNA methylation mapping of single cells still remain a challenge. Developments in DNA sequencing technologies as well as the methods for identification and mapping of 5-hydroxymethylcytosine are expected to augment our current understanding of epigenomics. Here we present an overview of methodologies available for DNA methylation analysis with special focus on recent developments in genome-wide and high-throughput methods. While the application focus relates to cancer research, the methods are equally relevant to broader issues of epigenetics and redox science in this special forum.

DNA transfer: informed judgment or mere guesswork?

With the advances of analytical sensitivity, it is now possible to detect a DNA profile from minute quantity of DNA. It opens new investigative avenues (in cold cases for example), but also new interpretative challenges. Here, forensic scientists deal with items bearing DNA cellular material from areas showing no visible stain and have limited means to identify the nature of the body fluid involved. Such DNA cells can be considered as trace evidence that can be exchanged for reasons connected to the alleged facts under investigation (generally a direct transfer) but also following alternative and versatile ways (through secondary or tertiary transfer) that have no connection to the facts under investigation. The trace becomes an ubiquitous material that can be found for unconnected reasons. In addition, and especially with trace quantities of DNA, the debate in court is less focused on the issue of the source of the DNA (often the parties will not dispute it), but on the mechanisms whereby the biological material has been transferred (Taroni et al., 2013). In other words, the well-known territory of source level DNA statistics (see Buckleton et al., 2005 for example) does not help with the interpretation process, but the forensic scientist is invited to assess how likely it would be to observe this amount of DNA given various transfer mechanisms. The review by Meakin and Jamieson (2013) led them to conclude that the quantity of DNA or the quality of the profile cannot be used “to reliably infer the mode of transfer by which the DNA came to be on the surface of interest.”

Specific magnetic isolation for direct detection of HPV16

Finding a suitable DNA purification system is vital for the success of many PCR based diagnostic tests. This report demonstrates the value of magnetic beads in combination with real-time PCR for the sequence-specific isolation and detection of episomal HPV16 DNA. In order to maximize the isolation, two purification procedures were evaluated. Compared to the indirect method, in which the target was magnetically labeled after being hybridized to the capture probes, much higher efficiencies were obtained by directly capturing the target using DNA functionalized beads. These higher efficiencies were obtained by carefully tuning the capture probe density on the beads. When modifying the beads with dual-biotinylated capture probes or introducing beads modified with different capture probes, the amount of HPV16 isolated from spiked clinical swab samples even increased further. This not only resulted in the use of dual-biotinylated capture probes in higher purification efficiencies, but also the thermostability of the DNA-bead linkage was found to improve. In summary, this study shows that DNA functionalized magnetic beads are very promising diagnostic tools as they allow for a specific, simple, and fast isolation and concentration of minute quantities of DNA from complex clinical samples.

A simple and innovative method for species identification of phytoplankton cells on minute quantities of DNA

Dinoflagellates belonging to the genus Alexandrium are often involved in harmful algal blooms. Their ecological exploration is thus essential to increase our knowledge on these toxic events. Yet, population genetic studies, taxonomic identification and environmental monitoring are hampered by major constraints: the necessity to establish monoclonal cultures from environmental samples and the sensitivity of available molecular tools. The present work describes a very simple and sensitive method for extraction and amplification of DNA at the infra-single-cell level. Its on-slide format allows for easy visual control of both quality and quantity of the templates. Combined with a semi-multiplex PCR protocol designed on the 18S-28S rDNA-ITS region of Alexandrium catenella and Alexandrium tamarense, this procedure allowed the identification and discrimination of these species from both monoclonal cultures and natural samples.

Whole-genome multiple displacement amplification from single cells

Multiple displacement amplification (MDA) is a recently described method of whole-genome amplification (WGA) that has proven efficient in the amplification of small amounts of DNA, including DNA from single cells. Compared with PCR-based WGA methods, MDA generates DNA with a higher molecular weight and shows better genome coverage. This protocol was developed for preimplantation genetic diagnosis, and details a method for performing single-cell MDA using the phi29 DNA polymerase. It can also be useful for the amplification of other minute quantities of DNA, such as from forensic material or microdissected tissue. The protocol includes the collection and lysis of single cells, and all materials and steps involved in the MDA reaction. The whole procedure takes 3 h and generates 1-2 microg of DNA from a single cell, which is suitable for multiple downstream applications, such as sequencing, short tandem repeat analysis or array comparative genomic hybridization.

MOLECULAR ANALYSIS OF SALVIA SPP. THROUGH RAPD MARKERS

INTRODUCTION The genus Salvia (fam. Labiatae) is one of the largest genera of flowering plants, with nearly 1,000 species from both the Old and New World, largely cultivated for ornamental, aromatic and culinary usage. The genus exhibits a remarkable range of morphological and ecological variation and poses numerous problems for the taxonomist and evolutionary biologist. The introduction of DNA-based analysis has provided many useful markers for genetic fingerprinting in order to study genetic diversity and to characterize unknown accessions. In the range of DNA-profiling methods, the RAPD (Random Amplified Polymorphic DNA) technique has been widely used for its simplicity in procedures, use of random arbitrary primers, costeffectiveness, and the requirement of minute quantities of DNA. In the framework of an European INTERREG ALCOTRA Project “SALVIE”, for the valorisation of new germplasm, we have used RAPD analysis to determine the genetic relationships among several sage genotypes of the collection of 150 sage accessions, established at C.R.A.Experimental Institute for Floriculture in Sanremo (ITALY). PLANT MATERIAL Seventeen accessions of sage were analysed: they included 12 different species, 4 cultivars and one hybrid (Table 1).

Whole Genome Amplification of DNA from Laser Capture-Microdissected Tissue for High-Throughput Single Nucleotide Polymorphism and Short Tandem Repeat Genotyping

Genome-wide screening of genetic alterations between normal and cancer cells, as well as among subgroups of tumors, is important for establishing molecular mechanism and classification of cancer. Gene silencing through loss of heterozygosity is widely observed in cancer cells and detectable by analyzing allelic loss of single nucleotide polymorphism and/or short tandem repeat markers. To use minute quantities of DNA that are available through laser capture microdissection (LCM) of cancer cells, a whole genome amplification method that maintains locus and allele balance is essential. We have successfully used a ø29 polymerase-based isothermal whole genome amplification method to amplify LCM DNA using a proteinase K lysis procedure coupled with a pooling strategy. Through single nucleotide polymorphism and short tandem repeat genotype analysis we demonstrate that using pooled DNA from two or three separate amplification reactions significantly reduces any allele bias introduced during amplification. This strategy is especially effective when using small quantities of source DNA. Although a convenient alkaline lysis DNA extraction procedure provided satisfactory results from using 1500 to 3000 LCM cells, proteinase K digestion was superior for lower cell numbers. Accurate genotyping is achieved with as few as 100 cells when both proteinase K extraction and pooling are applied.

Polymerase chain reaction as a diagnostic adjunct in herpesvirus infections of the nervous system.

Polymerase chain reaction (PCR) is a powerful technique that allows detection of minute quantities of DNA or RNA in cerebrospinal fluid (CSF), vesicle and endoneurial fluids, blood, fresh-frozen, and even formalin-fixed tissues. Various infectious agents can be detected with high specificity and sensitivity, including bacteria, parasites, rickettsia and viruses. PCR analysis of CSF has revolutionized the diagnosis of nervous system viral infections, particularly those caused by human herpesviruses (HHV), and has now replaced brain biopsy as the gold standard for diagnosis of herpes simplex virus (HSV) encephalitis. PCR analysis of both CSF and nervous system tissues has also broadened our understanding of the spectrum of disease caused by HSV-1 and -2, cytomegalovirus (CMV), Epstein-Barr virus (EBV), varicella zoster virus (VZV), and HHV-6. Nonetheless, positive tissue PCR results must be interpreted cautiously, especially in cases that lack corroborating clinical and neuropathologic evidence of infection. Moreover, positive PCR results from tissues do not distinguish latent from productive (lytic) viral infections. In several neurological diseases, negative PCR results have provided strong evidence against a role for herpesviruses as the causative agents. This review focuses on the use of PCR tests to diagnose HSV and VZV infections of the nervous system.

Representational difference analysis using minute quantities of DNA.

Representational difference analysis (RDA) is a differential hybridization method which can effectively isolate unique DNA sequences from complex and highly related genomes or cDNA libraries. A major drawback of the RDA analysis is the requirement for pure driver and relatively pure tester samples, ruling out the analysis of whole tissue biopsies. To circumvent this problem, we have modified the technique for the analysis of very small quantities of DNA so that pure cell populations isolated by micromanipulation from tissue sections can be analyzed. Using this modified technique, as few as 50 diploid cells ( approximately 500 pg of DNA) can be analyzed.

Identification of genetic polymorphisms in the 'expressed sequence tag' (EST) database

▼Genetic variation in the human population has beenstudied to gain insight into the functional importance ofspecific genes in disease and drug metabolism. For ex-ample, polymorphic variants of genes that are importantin the regulation of blood pressure, blood clotting andblood lipids are studied in relation to cardiovascular dis-ease (Ref. 1). The relation of detoxification enzymes to can-cer risk (Ref. 2, 3, 4, 5, 6, 7) and idiosyncratic drug effects(Ref. 8, 9), the latter with the aim to obtain individual-ized drug-therapy regimens, are the focus of world-wide ef-forts. Individual genotyping can now be performed quicklyand easily by PCR-based methods utilizing minute quan-tities of DNA. However, finding new unknown polymor-phisms in a gene is a tedious task involving either a searchfor restriction fragment length polymorphisms (RFLPs) onSouthern blots or PCR amplifications of suitably sized seg-mentsofthegene,followedbysingle-strand-conformation-polymorphism (SSCP) analysis or direct DNA-sequence de-termination. Because of the considerable interest in, andplans of, cataloguing human DNA sequence variation (Ref.10), improved methodology, including minisequencingstrategies, multiplex reverse dot blots, DNA chips and aTaqMan approach is being developed. However, we showhere that a considerable amount of human DNA sequencevariants can be found

Molecular tools in marine ecology

Molecular tools have diverse applications in marine ecology. In microbial systems, DNA sequences of rRNA and other genes have identified a variety of novel lineages of bacteria inhabiting marine environments that have resisted traditional culture methods. However, relatively few natural populations have been characterized due to the rather labor-intensive methodologies employed. Recent technological developments such as in situ PCR and flow cytometry promise to greatly enhance the speed at which microbial taxa can be identified and enumerated in field collected water and substrate samples; such advances will allow future work to employ the spatial and temporal field sampling required to monitor the impact of natural and anthropogenic changes in the environment. This approach also holds promise for examining physiological status of field collected cells, garnering information on such elusive parameters as growth rates and the extent of nutrient limitation under natural conditions. Studies of macrobiota have similarly benefited from the use of molecular approaches to species identification. This has been particularly true with regard to distinguishing among larval forms of closely related taxa which are nearly identical morphologically. Genetic variation within species assayed by molecular tools has been useful in examining the stability of populations through time and in assessing patterns of recruitment to geographically separated populations. Enhanced understanding of these ecological problems will also require intensive spatial and temporal monitoring of both larval and adult populations. Often, the newer techniques based on DNA sequence variation have practical advantages over allozyme techniques: e.g., PCR allows assay of minute quantities of DNA that may come from ethanol preserved samples. However, when ample allozyme variation exists to address a given issue, these older techniques may be favored on a variety of criteria, including speed and cost. Hence, choice of methodology should be based on the expected efficiency of a given approach to a specific problem rather than the apparent sophistication of the method itself.

Use of tagged random hexamer amplification (TRHA) to clone and sequence minute quantities of DNA--application to a 180 kb plasmid isolated from Sphingomonas F199.

We have developed a novel method to clone and sequence minute quantities of DNA. The method was applied to sequence a 180 kb plasmid pNL1. The first step was the production of a size distributed population of DNA molecules that were derived from the 180 kb plasmid pNL1. The first step was accomplished by a random synthesis reaction using Klenow fragment and random hexamers tagged with a T7 primer at the primer 5'-end (T7-dN6, 5'-GTAATACGACTCACTATAGGGCNNNNNN-3'. In the second step, Klenow-synthesized molecules were amplified by PCR using T7 primer (5'-GTAATACGACTCACTATAGGGC-3'). With a hundred nanograms starting plasmid DNA from pNL1, we were able to generate Klenow-synthesized molecules with sizes ranging from 28 bp to >23 kb which were detectable on an agarose gel. The Klenow-synthesized molecules were then used as templates for standard PCR with T7 primer. PCR products of sizes ranging from 0.3 to 1.3 kb were obtained for cloning and sequencing. From the same Klenow-synthesized molecules, we were also able to generate PCR products with sizes up to 23 kb by long range PCR. A total 232.5 kb sequences were obtained from 593 plasmid clones and over twenty putative genes were identified. Sequences from these 593 clones were assembled into 62 contigs and 99 individual sequence fragments with a total unique sequence of 86.3 kb.

The use of microsatellite analysis in population biology: background, methods and potential applications.

A promising technique currently emerging for population studies is the analysis of microsatellite DNAs. Microsatellite alleles offer several advantages over other types of molecular markers. They are abundant, highly variable, and can be assayed from minute quantities of DNA using PCR. Their major disadvantage is that it is usually necessary to screen genomic libraries to identify and characterize microsatellite loci for each species under investigation. The first goal of this chapter is to summarize background information having implications for population studies. This information comes primarily from human genome literature and is therefore not easily accessible to many population biologists. Secondly, because microsatellite analysis uses molecular approaches that are new to most population biologists, we attempt to provide a rationale and overview of methodology. Finally, we review population studies to date that have used microsatellite analysis and offer our perspective on the potential for future studies.

Parentage determination in maize hybrids using the arbitrarily primed polymerase chain reaction (AP-PCR)

Using a novel procedure based on the polymerase chain reaction, we have developed a rapid, efficient, and economical method for identifying plant genotypes. The arbitrarily primed polymerase chain reaction (AP-PCR) generates reproducible fingerprints from any organism, without the need for DNA sequence information. These fingerprints include DNA fragment polymorphisms that can be (1) used for varietal identification and parentage determination, (2) followed in segregating populations produced by crosses, (3) used as markers for the construction of genetic maps, and (4) used to generate dendograms of phylogenetic relationships, especially at the intraspecific level. AP-PCR requires only minute quantities of DNA (10-25 ng per reaction) and therefore can be used in situations in which DNA is limiting. We demonstrate the use of AP-PCR to identify inbred parents of hybrid maize plants in double-blind experiments.

Detection of Epstein-Barr virus genomes in normal human lacrimal glands

Epstein-Barr virus (EBV) has been implicated in several ocular diseases; however, detection of the EBV genome in ocular tissues has not been documented. We report the detection of amplified EBV genomic sequences in 11 of 26 normal lacrimal gland DNA samples by using the polymerase chain reaction. Serum was available for 19 of the lacrimal gland donors. All 19 were EBV seropositive, although of the 19 lacrimal gland-seropositive patients, EBV sequences were detected in only 10 of the samples. Further, amplified EBV sequences were not detected in circulating lymphocyte DNA from normal seropositive volunteers, most likely because of the low frequency of circulating EBV-infected B cells. Amplification of EBV from cadaver lacrimal gland DNA was possible with minute quantities of DNA, whereas peripheral blood mononuclear cell DNA from normal volunteers did not amplify EBV sequences. Interestingly, the peripheral blood mononuclear cell polymerase chain reactions contained approximately 100 times more DNA than the lacrimal gland polymerase chain reactions. We conclude that the lacrimal gland may be a site for EBV persistence and that positive EBV serology is not an indicator of which individuals may have EBV harbored within their lacrimal glands.