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Molecular Pathology

DNA purification

Introduction and History

Author: Rodney E. Shackelford, D.O., Ph.D. (see Reviewers page)
Revised: 14 April 2012, last major update April 2012
Copyright: (c) 2008-2012, PathologyOutlines.com, Inc.


● Extremely pure nucleic acid samples (RNA or DNA) are required by molecular, research and forensic molecular testing techniques such as PCR-amplification of target nucleic sequences, sequencing, blotting/strip assays and cloning procedures
● Often the target nucleic acids must initially be isolated from crude samples that are often contaminated with organic or inorganic substances that can inhibit the PCR reaction or other aspects of DNA amplification
● Additionally, many target nucleic acid in crude samples are unstable and easily degraded or chemically modified by DNases, RNases, formaldehyde
● Rapid, efficient sample processing is often vital to insure sufficiently intact nucleic acid for testing protocols
● Contaminating exogenous nucleic acids can enter samples during the isolation procedure, leading to false positive results and possible treatment errors; for these reasons, prompt, effective and cost-efficient nucleic acid isolation techniques are vital


● Nucleic acids first isolated in 1869 by Friedrich Miescher, who identified a chemical in the nuclei of leukocytes that was rich in phosphate and nitrogen and lacking sulfur; named "nuclein", due to derivation from nucleus
● Later, Albrect Kossel isolated the non-protein content of nuclein, finding adenine, cytosine, guanine, thymine and uracil from nuclein, giving some information about the molecular structure of DNA
● Other researchers isolated and identified the chemically linked base-sugar-phosphate nucleotide unit and identified sugar and base differences between RNA and DNA
● Initial nucleic acid preparations were crude and mainly depended on various buffered salt solutions with acid and alkali washes to precipitate and isolate nucleic acids
● “Warm alcohol” was used to remove lipids, pepsin was used to digest proteins
● Since these early efforts, enormous progress has been made in nucleic acid isolation and many highly effective techniques are now used for different applications

End of Molecular Pathology > DNA purification > Introduction and History

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