Diseases, Conditions, Syndromes

Researchers identify previously unknown bacterial strain

Clinicians at the Department of Neurology of MedUni Vienna/Vienna General Hospital identified muscle weakness and severe fatigue in a previously healthy patient, to the extent that he was soon confined to a wheelchair. These ...

HIV & AIDS

Cellphone technology developed to detect HIV

The management of human immunodeficiency virus 1 (HIV), an autoimmune disorder that cripples the immune system by attacking healthy cells, remains a major global health challenge in developing countries that lack infrastructure ...

Diseases, Conditions, Syndromes

Quick identification of multidrug-resistant pathogens

If doctors diagnose a patient with blood poisoning, the patient will immediately be administered a broad-spectrum antibiotic. In many cases, however, the drug is ineffective. Multidrug-resistant pathogens are often the reason ...

Diseases, Conditions, Syndromes

Screening blood donations for Zika virus is costly, low yield

(HealthDay)—Screening blood donations for Zika virus (ZIKV) in the United States is costly with low yield, according to a study published in the May 10 issue of the New England Journal of Medicine.

Pediatrics

Human rhinovirus commonly detected in febrile infants

(HealthDay)—For febrile infants, human rhinovirus (HRV) is common, and detection does not alter risk of concomitant urinary tract infection or invasive bacterial infection, according to a study published online Jan. 17 ...

Diseases, Conditions, Syndromes

Patient's psoriasis improves with initiation of hepatitis C therapy

Researchers report the first case of a patient whose psoriasis improved when therapy for his hepatitis C virus (HCV) infection was initiated. Findings from a brief case report are published in Annals of Internal Medicine.

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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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