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Author

Phi Nga Nguyen

Bio: Phi Nga Nguyen is an academic researcher from Baylor College of Medicine. The author has contributed to research in topics: Multiplex polymerase chain reaction & Multiple displacement amplification. The author has an hindex of 8, co-authored 9 publications receiving 2320 citations. Previous affiliations of Phi Nga Nguyen include Baylor University & Howard Hughes Medical Institute.

Papers
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Journal ArticleDOI
TL;DR: This procedure utilizes simultaneous genomic DNA amplification of multiple widely separated sequences and should permit deletion scanning at any hemizygous locus and it is demonstrated the application of this multiplex reaction for prenatal and postnatal diagnosis of DMD.
Abstract: 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.

1,323 citations

Journal ArticleDOI
01 Jun 1990-Genomics
TL;DR: The elucidation of the complete DNA sequence of the human H PRT gene locus has enabled the construction of multiple oligonucleotide primer sets for the simultaneous in vitro amplification of all nine HPRT exons, and the multiplex polymerase chain reaction provides a facile assay for the detection of HPRt exon deletions.

321 citations

Journal ArticleDOI
TL;DR: It is demonstrated that the direct DNA sequence analysis can be automated, further simplifying the detection of new mutations at this locus and allowing DNA diagnosis and carrier identification by the direct detection of the mutant alleles within individual families affected by LN.
Abstract: The Lesch-Nyhan (LN) syndrome is a severe X chromosome-linked disease that results from a deficiency of the purine salvage enzyme hypoxanthine phosphoribosyltransferase (HPRT). The mutations leading to the disease are heterogeneous and frequently arise as de novo events. We have identified nucleotide alterations in 15 independently arising HPRT-deficiency cases by direct DNA sequencing of in vitro amplified HPRT cDNA. We also demonstrate that the direct DNA sequence analysis can be automated, further simplifying the detection of new mutations at this locus. The mutations include DNA base substitutions, small DNA deletions, a single DNA base insertion, and errors in RNA splicing. The application of these procedures allows DNA diagnosis and carrier identification by the direct detection of the mutant alleles within individual families affected by LN.

282 citations

Journal ArticleDOI
TL;DR: Competitive oligonucleotide priming provides a simple general strategy for the detection of single DNA base differences.
Abstract: Synthetic DNA oligonucleotides can serve as efficient primers for DNA synthesis even when there is a single base mismatch between the primers and the corresponding DNA template. However, when the primer-template annealing is carried out with a mixture of primers and at low stringency the binding of a perfectly matched primer is strongly favored relative to a primer differing by a single base. This primer competition is observed over a range of oligonucleotide sizes from twelve to sixteen bases and with a variety of base mismatches. When coupled with the polymerase chain reaction, for the amplification of specific DNA sequences, competitive oligonucleotide priming provides a simple general strategy for the detection of single DNA base differences.

273 citations

Journal ArticleDOI
TL;DR: Evidence is provided of a continuous spectrum of sequence diversity between any two isolates ranging from those derived from the same person to those from close contacts and, ultimately, those from unrelated individuals.
Abstract: The degree of change in the nucleotide sequence of human immunodeficiency virus type 1 (HIV-1) that occurs when it is transmitted sexually from one individual to another or vertically from mother to child is unknown. Previous studies have shown that most cultured HIV-1 isolates from the same individuals differed in the entire envelope gene nucleotide sequence by up to 2%, although most isolates from unrelated individuals differed by 6-22%. To examine diversity among HIV-1 isolates from close contacts, we determined the nucleotide sequences of viruses from a family with a known epidemiologic profile, in which a woman transmitted HIV-1 heterosexually to her partner and vertically to her daughter. Direct DNA sequence analysis of primary HIV-1 isolates amplified by PCR was used to distinguish the major and minor viral sequences, termed quasispecies, to rapidly determine the predominant sequences and their phylogenetic relationships. The nucleotide sequence diversity of a major portion of the HIV-1 envelope gene was 3.7% between isolates from the woman and her heterosexual partner and 8.5% between isolates from this woman and her daughter, who had been infected for a longer period than the partner. The configuration of the phylogenetic tree demonstrated that the daughter's predominant isolate evolved from a progenitor of her mother's current strain. This study provides evidence of a continuous spectrum of sequence diversity between any two isolates ranging from those derived from the same person to those from close contacts and, ultimately, those from unrelated individuals. These data and methods can be applied to epidemiologic investigations of possible HIV-1 transmission between health care workers and their patients.

71 citations


Cited by
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Journal ArticleDOI
TL;DR: 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.
Abstract: 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.

3,050 citations

Journal ArticleDOI
05 Sep 2008-Cell
TL;DR: The generation of induced pluripotent stem cells from patients with a variety of genetic diseases with either Mendelian or complex inheritance are described, offering an unprecedented opportunity to recapitulate both normal and pathologic human tissue formation in vitro, thereby enabling disease investigation and drug development.

2,195 citations

Journal ArticleDOI
01 Feb 1992-Genomics
TL;DR: The results suggest that trimeric and tetrameric STR loci are useful markers for the study of new mutations and genetic linkage analysis and for application to personal identification in the medical and forensic sciences.

1,474 citations

Journal ArticleDOI
06 Mar 1992-Science
TL;DR: These studies suggest that the mutational mechanism leading to DM is triplet amplification, similar to that occurring in the fragile X syndrome.
Abstract: Synthetic oligonucleotides containing GC-rich triplet sequences were used in a scanning strategy to identify unstable genetic sequences at the myotonic dystrophy (DM) locus. A highly polymorphic GCT repeat was identified and found to be unstable, with an increased number of repeats occurring in DM patients. In the case of severe congenital DM, the paternal triplet allele was inherited unaltered while the maternal, DM-associated allele was unstable. These studies suggest that the mutational mechanism leading to DM is triplet amplification, similar to that occurring in the fragile X syndrome. The triplet repeat sequence is within a gene (to be referred to as myotonin-protein kinase), which has a sequence similar to protein kinases.

1,411 citations

Journal ArticleDOI
TL;DR: 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 are reported.
Abstract: 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.

1,403 citations