| 1. |
- Ahmadian, Afshin, et al.
(författare)
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A brief history of genetic variation analysis
- 2002
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Ingår i: BioTechniques. - 0736-6205 .- 1940-9818. ; 32:5, s. 1122-
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Forskningsöversikt (refereegranskat)abstract
- As the human genome sequence is determined, there is an emerging need for the analysis of human sequence variations as genetic markers in diagnosis, linkage and association studies, cancer research, and pharmacogenomics. There are several different techniques and approaches for detecting these genetic variations, and here we review some of these techniques and their application fields. However, all the techniques have advantages and disadvantages, and factors such as laboratory instrumentation, personnel experience, required accuracy, required throughput, and cost often have to be taken into account before selecting a method.
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| 2. |
- Ahmadian, Afshin, et al.
(författare)
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Analysis of the p53 tumor suppressor gene by pyrosequencing
- 2000
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Ingår i: BioTechniques. - : Future Science Ltd. - 0736-6205 .- 1940-9818. ; 28:1, s. 140-
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Tidskriftsartikel (refereegranskat)abstract
- Tumor suppressor genes are implicated in cell cycle progression. Inactivation of these genes predominantly occurs through mutations and/or allelic loss that involves both alleles. With inactivation by multiple mutations in a single gene, cloning of the amplified gene is necessary to determine whether the mutations reside on one ol both alleles. Using pyrosequencing, a recently developed approach based on sequencing-by-synthesis, we studied genetic variability in the p53 tumor suppressor gene and could quantify the ratio between the mutated and wild-type amplified fragments. Further-more, this sequencing technique also allows allelic determination of adjacent mutations with no cloning of amplified fragments.
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| 3. |
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| 4. |
- Allen, Marie, et al.
(författare)
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Allele-specific HLA-DRB1 amplification of forensic evidence samples with mixed genotypes
- 1995
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Ingår i: BioTechniques. - 0736-6205 .- 1940-9818. ; 19:3, s. 454-463
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Tidskriftsartikel (refereegranskat)abstract
- A major problem in analyzing forensic casework samples is the presence of genetic material from more than one individual in the material evidence. For instance, in sexual assault cases the evidence (vaginal swabs) usually contains a majority of vaginal epithelial cells and varying amounts of sperm cells from the perpetrator. Samples with mixed genotypes are also common among other biological evidence materials such as nail scrapes and mixed bloodstains. We have developed an allele-specific amplification system for the highly polymorphic HLA class II DRB1 locus that permits the detection of individual alleles in a sample with mixed genotypes, independent of the initial frequency of the alleles. Using a set of eight allele-specific amplification primers and typing the amplified fragments with sequence-specific probes, most of the 60 DRB1 alleles can be resolved. The method is highly specific and sensitive, with the potential for amplifying 15 copies of a particular allele in a background of 3 x 10(5) copies of other alleles. The method was successfully applied to three forensic cases, where the material evidence consisted of sperm stains on panties, nail scrapes and bloodstains on skin. Thus the DRB1 allele-specific amplification system can be employed for the unambiguous determination of the presence of individual alleles in materials suspected to contain mixed genotypes, even when the alleles of interest constitute only a small fraction of the total DNA
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| 5. |
- Allen, Marie, et al.
(författare)
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PCR-based DNA typing of saliva on stamps and envelopes
- 1994
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Ingår i: BioTechniques. - 0736-6205 .- 1940-9818. ; 17:3, s. 546-552
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Tidskriftsartikel (refereegranskat)abstract
- In forensic cases involving mail bombs, extortion, kidnapping or threatening letters, biological evidence such as the saliva used to attach the stamp and seal the envelope could be used for genetic analysis. We have developed a highly sensitive semi-nested PCR method for the HLA-DRB1 locus; suitable for the analyses of very limited amounts of DNA. When applied to a set of stamps and envelopes with saliva from control individuals, typing results were consistent with those obtained using hairs drawn from the same individuals. No interference was found due to DNA from the fingerprints of people handling the letters. The system was applied to three forensic cases with threatening letters. The first case resulted in an exclusion of the suspect. In the second case, the suspect could not be excluded (probability of identical genotype by chance > 0.01). These results demonstrate that biological evidence in cases with threatening letters is amenable to genetic typing.
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| 6. |
- Andersson, T., et al.
(författare)
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Monitoring of representational difference analysis subtraction procedures by global microarrays
- 2002
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Ingår i: BioTechniques. - : Future Science Ltd. - 0736-6205 .- 1940-9818. ; 32:6, s. 1348-
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Tidskriftsartikel (refereegranskat)abstract
- Various approaches to the study of differential gene expression are applied to compare cell lines and tissue samples in a wide range of biological contexts. The compromise between focusing on only the important genes in certain cellular processes and achieving a complete picture is critical for the selection of strategy. We demonstrate how global microarray technology can be used for the exploration of the differentially expressed genes extracted through representational difference analysis (RDA). The subtraction of ubiquitous gene fragments from the two samples was demonstrated using cDNA microarrays including more than 32 000 spotted, PCR-amplified human clones. Hybridizations indicated the expression of 9100 of the microarray elements in a macrophage/foam cell atherosclerosis model system, of which many were removed during the RDA process. The stepwise subtraction procedure was demonstrated to yield an efficient enrichment of gene fragments overrepresented in either sample (18% in the representations, 86% after the first subtraction, and 88% after the second subtraction), many of which were impossible to detect in the starting material. Interestingly, the method allowed for the observation of the differential expression of several members of the low-abundant nuclear receptor gene family. We also observed a certain background level in the difference products of nondifferentially expressed gene fragments, warranting a verification strategy for selected candidate genes. The differential expression of several genes was verified by real-time PCR.
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| 7. |
- Andréasson, Hanna, et al.
(författare)
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Mitochondrial sequence analysis for forensic identification using Pyrosequencing technology
- 2002
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Ingår i: BioTechniques. - 0736-6205 .- 1940-9818. ; 32:1, s. 124-6, 128, 130-3
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Tidskriftsartikel (refereegranskat)abstract
- Over recent years, requests for mtDNA analysis in the field of forensic medicine have notably increased, and the results of such analyses have proved to be very useful in forensic cases where nuclear DNA analysis cannot be performed. Traditionally, mtDNA has been analyzed by DNA sequencing of the two hypervariable regions, HVI and HVII, in the D-loop. DNA sequence analysis using the conventional Sanger sequencing is very robust but time consuming and labor intensive. By contrast, mtDNA analysis based on the pyrosequencing technology provides fast and accurate results from the human mtDNA present in many types of evidence materials in forensic casework. The assay has been developed to determine polymorphic sites in the mitochondrial D-loop as well as the coding region to further increase the discrimination power of mtDNA analysis. The pyrosequencing technology for analysis of mtDNA polymorphisms has been tested with regard to sensitivity, reproducibility, and success rate when applied to control samples and actual casework materials. The results show that the method is very accurate and sensitive; the results are easily interpreted and provide a high success rate on casework samples. The panel of pyrosequencing reactions for the mtDNA polymorphisms were chosen to result in an optimal discrimination power in relation to the number of bases determined.
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| 8. |
- Andréasson, H., et al.
(författare)
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Real-Time DNA Quantification of Nuclear and Mitochondrial DNA in Forensic Analysis
- 2002
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Ingår i: BioTechniques. - 0736-6205 .- 1940-9818. ; 33:2, s. 402-411
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Tidskriftsartikel (refereegranskat)abstract
- The rapid development of molecular genetic analysis tools has made it possible to analyze most biological materialfound at the scene of a crime. Evidence materials containing DNA quantities too low to be analyzed using nuclear markers can be analyzed using the highly abundant mtDNA. However, there is a shortage of sensitive nDNA and mtDNA quantification assays. In this study, an assay for the quantification of very small amounts of DNA, based on the real-time Taq-Man assay, has been developed. This analysis will provide an estimate of the total number of nDNA copies and the total number of mtDNA molecules in a particular evidence material. The quantification is easy to perform, fast, and requires a minimum of the valuable DNA extracted from the evidence materiaL The results will aid in the evaluation of whether the specific sample is suitable for nDNA or mtDNA analysis. Furthermore, the optimal amount of DNA to be used in further analysis can be estimated ensuring that the analysis is successful and that the DNA is retained for future independent analysis. This assay has significant advantages over existing techniques because of its high sensitivity, accuracy, and the combined analysis of nDNA and mtDNA. Moreover, it has the potential to provide additional information about the presence of inhibitors in forensic samples. Subsequent mitochondrial and nuclear analysis of quantified samples illustrated the potential to predict the number of DNA copies required for a successful analysis in a certain typing assay.
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| 9. |
- Bar, Tzachi, 1970, et al.
(författare)
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Kinetics quality assessment for relative quantification by real-time PCR
- 2005
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Ingår i: BioTechniques. - 0736-6205 .- 1940-9818. ; 39:3, s. 333-
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Tidskriftsartikel (refereegranskat)abstract
- For proper relative quantification by real-time PCR, compared samples should have similar PCR efficiencies. To test this prerequisite, we developed two quality tests: (i) adjustment of a test for kinetic outlier detection (KOD) to relative quantification; and (ii) comparison of the efficiency variance of test samples with the efficiency variance of samples with highly reproducible quantification. The tests were applied on relative quantification of two genes in 30 sets of 5 replicate samples (same treatment, different animals). Ten low-quality sets and 28 outliers were identified. The low-quality sets showed higher coefficient of variation (cv)% of DNA quantities in replicate experiments than high-quality sets (63% versus 26%; P = 0.001) and contained a higher proportion of outlying quantities (35% versus 5.9%; P = 0.001) when individual samples were detected by adjusted KOD. Outlier detection with adjusted KOD reduced thefalse detection of outliers by 213 compared with the previous, nonadjusted version of KOD (20% versus 5.9%; P = 0.001). We conclude that the presented tests can be used to assign technical reasons to outlying observations.
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| 10. |
- Barken, K. B., et al.
(författare)
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Effect of unlabeled helper probes on detection of an RNA target by bead-based sandwich hybridization
- 2004
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Ingår i: BioTechniques. - 0736-6205 .- 1940-9818. ; 36:1, s. 124-
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Tidskriftsartikel (refereegranskat)abstract
- Unlabeled helper oligonucleotides assisting a bead-based sandwich hybridization assay were tested for the optimal placement of the capture and detection probes. The target used was a full-length in vitro synthesized mRNA molecule. Helper probes complementary to regions adjacent to the binding site of the 5' end attached capture probe were found much more effective than helper probes targeting positions adjacent to the detection probe binding site. The difference is believed to be caused by a disruption of the RNA secondary structure in the area where the capture probe binds, thereby reducing structural interference from the bead. The use of additional helpers showed an additive effect. Using helpers, at both sides of the capture and detection probes showed a 15- to 40-fold increase in hybridization efficiency depending on the target, thereby increasing the sensitivity of the hybridization assays. Using an electrical chip linked to the detection probe for the detection of p-ominophenol, which is produced by alkaline phosphatase, a detection limit of 2 x 10(-13) M mRNA molecules was reached without the use of a nucleic acid amplification step.
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