The 5'----3' exonuclease activity of the thermostable enzyme Thermus aquaticus DNA polymerase may be employed in a polymerase chain reaction product detection system to generate a specific detectable signal concomitantly with amplification. An oligonucleotide probe, nonextendable at the 3' end, labeled at the 5' end, and designed to hybridize within the target sequence, is introduced into the polymerase chain reaction assay. Annealing of probe to one of the polymerase chain reaction product strands during the course of amplification generates a substrate suitable for exonuclease activity. During amplification, the 5'----3' exonuclease activity of T. aquaticus DNA polymerase degrades the probe into smaller fragments that can be differentiated from undegraded probe. The assay is sensitive and specific and is a significant improvement over more cumbersome detection methods.

https://www.pnas.org/content/pnas/88/16/7276.full.pdf

Detection of specific polymerase chain reaction product by utilizing the 5'----3' exonuclease activity of Thermus aquaticus DNA polymerase.

Disease-Specific Induced Pluripotent Stem Cells

Genetic variation at five trimeric and tetrameric tandem repeat loci in four human population groups.

Full characterization of methicillin-resistant Staphylococcus aureus (MRSA) requires definition of not only the bacterial genetic background but also the structure of the complex and heterologous mec element these bacteria carry, which is associated with drug resistance determinant mecA. We report the development, validation, and application of a multiplex PCR strategy that allows quick presumptive characterization of the mec element types based on the structural features that were shown to be typical of mec elements carried by several MRSA clones. The strategy was validated by using a representative collection of pandemic MRSA clones in which the full structure of the associated mec elements was previously determined by hybridization and PCR screenings and also by DNA sequencing. The method was tested together with multilocus sequence typing and other typing methods for the characterization of 18 isolates representative of the MRSA clones recovered during a hospital outbreak in Barcelona, Spain. The multiplex PCR was shown to be rapid, robust, and capable in a single assay of identifying five structural types of the mec element among these strains, three major and two minor variants, each one of which has been already been seen among MRSA characterized earlier. This technique should be a useful addition to the armamentarium of molecular typing tools for the characterization of MRSA clonal types and for the rapid tentative identification of structural variants of the mec element.

Multiplex PCR Strategy for Rapid Identification of Structural Types and Variants of the mec Element in Methicillin-Resistant Staphylococcus aureus

The use of the polymerase chain reaction (PCR) in molecular diagnostics has increased to the point where it is now accepted as the gold standard for detecting nucleic acids from a number of origins and it has become an essential tool in the research laboratory. Real-time PCR has engendered wider acceptance of the PCR due to its improved rapidity, sensitivity, reproducibility and the reduced risk of carry-over contamination. There are currently five main chemistries used for the detection of PCR product during real-time PCR. These are the DNA binding fluorophores, the 5' endonuclease, adjacent linear and hairpin oligoprobes and the self-fluorescing amplicons, which are described in detail. We also discuss factors that have restricted the development of multiplex real-time PCR as well as the role of real-time PCR in quantitating nucleic acids. Both amplification hardware and the fluorogenic detection chemistries have evolved rapidly as the understanding of real-time PCR has developed and this review aims to update the scientist on the current state of the art. We describe the background, advantages and limitations of real-time PCR and we review the literature as it applies to virus detection in the routine and research laboratory in order to focus on one of the many areas in which the application of real-time PCR has provided significant methodological benefits and improved patient outcomes. However, the technology discussed has been applied to other areas of microbiology as well as studies of gene expression and genetic disease.

/pdf/real-time-pcr-in-virology-cln3j5i0kf.pdf

Real-time PCR in virology

The application of recombinant DNA technology to prenatal diagnosis of many recessively inherited X-linked diseases is complicated by a high frequency of heterogeneous, new mutations (1). Partial gene deletions account for more than 50% of Duchenne muscular dystrophy (DMD) lesions, and approximately one-third of all cases result from a new mutation (2-5). We report the isolation and DNA sequence of several deletion prone exons from the human DMD gene. We also describe a rapid method capable of detecting the majority of deletions in the DMD gene. This procedure utilizes simultaneous genomic DNA amplification of multiple widely separated sequences and should permit deletion scanning at any hemizygous locus. We demonstrate the application of this multiplex reaction for prenatal and postnatal diagnosis of DMD.

Joel E. Rainer

Papers

Deletion screening of the Duchenne muscular dystrophy locus via multiplex DNA amplification

Multiplex genomic DNA amplification for deletion detection

Amplification d'ADN des génomes multiples pour détecter des délétions

Multiple genomische DNA-Verstärkung zum Nachweis einer Deletion