News tagged with polymerase chain reaction

Related topics: dna

Human breast milk microbiome changes over time

(HealthDay)—The microbiome of breast milk is influenced by many factors, including maternal weight and how the baby was delivered, according to research published in the American Journal of Clinical Nu ...

Jan 28, 2013
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Association between virus, bladder cancers detected

A Lawrence Livermore National Laboratory (LLNL)-developed biological detection technology has been employed as part of an international collaboration that has detected a virus in bladder cancers.

Sep 11, 2013
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New method for early detection of colon cancer

A new, highly sensitive method to detect genetic variations that initiate colon cancer could be readily used for noninvasive colon cancer screening, according to a study published in Cancer Prevention Research, a journal of the ...

Sep 04, 2013
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Sugar coating reveals black death

Even today, the lives of humans and animals are claimed by plague. A new antibody-based detection method can be used to reliably and sensitively identify plague in patient serum and other biological samples. The antibody ...

Jul 17, 2013
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Polymerase chain reaction

In molecular biology, the polymerase chain reaction (PCR) is a technique to amplify a single or few copies of a piece of DNA across several orders of magnitude, generating millions or more copies of a particular DNA sequence. The method relies on thermal cycling, consisting of cycles of repeated heating and cooling of the reaction for DNA melting and enzymatic replication of the DNA. Primers (short DNA fragments) containing sequences complementary to the target region along with a DNA polymerase (after which the method is named) are key components to enable selective and repeated amplification. As PCR progresses, the DNA generated is itself used as a template for replication, setting in motion a chain reaction in which the DNA template is exponentially amplified. PCR can be extensively modified to perform a wide array of genetic manipulations.

Almost all PCR applications employ a heat-stable DNA polymerase, such as Taq polymerase, an enzyme originally isolated from the bacterium Thermus aquaticus. This DNA polymerase enzymatically assembles a new DNA strand from DNA building blocks, the nucleotides, by using single-stranded DNA as a template and DNA oligonucleotides (also called DNA primers), which are required for initiation of DNA synthesis. The vast majority of PCR methods use thermal cycling, i.e., alternately heating and cooling the PCR sample to a defined series of temperature steps. These thermal cycling steps are necessary to physically separate the strands (at high temperatures) in a DNA double helix (DNA melting) used as the template during DNA synthesis (at lower temperatures) by the DNA polymerase to selectively amplify the target DNA. The selectivity of PCR results from the use of primers that are complementary to the DNA region targeted for amplification under specific thermal cycling conditions.

Developed in 1984 by Kary Mullis, PCR is now a common and often indispensable technique used in medical and biological research labs for a variety of applications. These include DNA cloning for sequencing, DNA-based phylogeny, or functional analysis of genes; the diagnosis of hereditary diseases; the identification of genetic fingerprints (used in forensic sciences and paternity testing); and the detection and diagnosis of infectious diseases. In 1993 Mullis was awarded the Nobel Prize in Chemistry for his work on PCR.

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