What is RT-PCR?

 

RT-PCR is the common name for Reverse Transcription Polymerase Chain Reaction, which is a technique combining reverse trancsription of RNA into DNA and the amplification of specific target DNA by applying Polymerase Chain Reaction (PCR). The primary purpose of RT-PCR is to measure the amount of a specific RNA. 

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In order to detect a virus such as COVID-19 early in the body using real time RT–PCR, scientists need to convert the RNA to DNA through a process called ‘reverse transcription’. They do this because only DNA can be copied or amplified which is a key part of the real time RT–PCR process for detecting viruses.

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How does RT–PCR work with the COVID-19 virus?

 

A sample is collected from a person's nose or throat where the COVID-19 virus gathers. The sample is treated with several chemical solutions to remove substances such as proteins and fats and that extract only the RNA present. The RNA is reverse transcribed to DNA using a specific enzyme. Additional short fragments of DNA then added, that are complementary to specific parts of the transcribed viral DNA. If the virus is present in a sample, these fragments attach themselves to target sections of the viral DNA.

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The mixture is then placed in an RT–PCR machine. The machine cycles use the temperatures to heat and cool the mixture to trigger specific chemical reactions that create new, identical copies of the target sections of viral DNA. The cycle is repeated over and over to continue copying the target sections of viral DNA.

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As new copies of the viral DNA sections are built, the marker labels attach to the DNA strands and then release a fluorescent dye. The computer tracks the amount of fluorescence in the sample after each cycle. When a certain level of fluorescence is surpassed, this confirms that the virus is present. 

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