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Evolution of DNA sequencing.

Author(s)
Hamid Nawaz Tipu Department of Pathology, Combined Military Hospital, Khuzdar Cantt, Baluchistan, Pakistan
Ambreen Shabbir Department of Oral Pathology, Institute of Dentistry, CMH Medical College, Lahore, Pakistan
Abstract
Sanger and coworkers introduced DNA sequencing in 1970s for the first time. It principally relied on termination of growing nucleotide chain when a dideoxythymidine triphosphate (ddTTP) was inserted in it. Detection of terminated sequences was done radiographically on Polyacrylamide Gel Electrophoresis (PAGE). Improvements that have evolved over time in original Sanger sequencing include replacement of radiography with fluorescence, use of separate fluorescent markers for each nucleotide, use of capillary electrophoresis instead of polyacrylamide gel electrophoresis and then introduction of capillary array electrophoresis. However, this technique suffered from few inherent limitations like decreased sensitivity for low level mutant alleles, complexities in analyzing highly polymorphic regions like Major Histocompatibility Complex (MHC) and high DNA concentrations required. Several Next Generation Sequencing (NGS) technologies have been introduced by Roche, Illumina and other commercial manufacturers that tend to overcome Sanger sequencing limitations and have been reviewed. Introduction of NGS in clinical research and medical diagnostics is expected to change entire diagnostic approach. These include study of cancer variants, detection of minimal residual disease, exome sequencing, detection of Single Nucleotide Polymorphisms (SNPs) and their disease association, epigenetic regulation of gene expression and sequencing of microorganisms genome.
Publication Details
Page(s) 210-215
DOI DOI not available
Published Journal: Journal of College of Physicians and Surgeons--Pakistan : JCPSP, Volume: 25, Issue: 3, Year: 2015

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