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Polymerase chain reaction

Related Terms

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Background

  • DNA, short for deoxyribonucleic acid, is the name of the complex biological compound that makes up the genetic "blueprint" to make a living organism. The unique twisted ladder shape of DNA is called a double helix. The sides of DNA's double helix are made of alternating sugar and phosphate molecules while the "rungs" of the "ladder" are made of corresponding pairs of small molecules (each one half of the "rung") called bases. There are four different types of bases in DNA: adenine (A), thymine (T), cytosine (C), and guanine (G); the order in which they occur is referred to as the DNA sequence. Each base has a complement; that is, a base it usually pairs with: adenine is complementary to thymine, and cytosine to guanine. Due to their chemical structure these molecules are sometimes called nitrogenous or nucleotide bases. A sequence of three base pairs is called a codon. A codon is the fundamental unit of the genetic code, with each of the 64 possible 3-base sequences corresponding to a particular instruction: start, stop, or one of 20 amino acids. The biochemical machinery within a cell "reads" a DNA strand, eventually translating a series of codons into long chains of amino acids. These amino acid-chains fold to form proteins, complex molecules whose structure and function underlie all biological life. In all, the human genome, one complete copy of all the DNA containing the code for a human being, is three billion base pairs long. However, only a small percentage of the genome codes for proteins or has any other known function.
  • Polymerase chain reaction (PCR) is a scientific method used commonly in molecular biology. Its name is based on one of its key components, an enzyme (biomolecules which aid certain chemical reactions) called DNA polymerase, which is used to replicate a piece of DNA. During PCR, each strand of DNA's double helix is separated (that is, the "ladder" of DNA is divided lengthwise, as if cut through the "rungs") from the other with heat (a process called denaturation) and then used by DNA polymerase as a template to make the complementary strand. Each replicated piece of DNA can then serve as a template for further replication, setting in motion a chain reaction in which the selected sequence of DNA is exponentially replicated. Two strands become four, four become eight, and so on. The amplified DNA product (so called as it has been replicated many times over) can then be used for a variety of molecular biological tests and procedures, often by allowing detection or large scale production of a particular sequence. One example is DNA cloning, wherein a DNA sequence is isolated and amplified in a living organism. Another is using PCR to allow detection of a genetic mutation in an individual suspected of having a genetic disorder.
  • The PCR technique was developed in 1983 and is generally credited to Kary Mullis; he later won the Nobel Prize for this work. PCR is now commonly used in medical and biological research in a variety of applications, including DNA cloning, functional analysis of genes, diagnosis of hereditary diseases, genetic fingerprinting for use in forensics and paternity testing, and the detection and diagnosis of infectious diseases.

Methods

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Research

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Implications

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Limitations

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Safety

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Future Research

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Author Information

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References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

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The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.