In this 2020, most of us kept bothering and worrying about one thing, that is 'Corona virus'. This cruel virus make everyone of us to lock ourselves in our home.
In this bad phase, we usually came across the terms "Number of cases" and "Number of samples tested" in news and newspapers which is becoming one of the most common things to hear in our life now.
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Even we came across one important news that the samples have been tested using "RT-PCR".
In this blog we are going to briefly explain about the process of RT PCR and how the Covid-19 (Cov- Corona virus & id-19 refers to protein coat) samples are tested.
Let's jump in. Lockdown is only for our body not our mind.
What is this RT-PCR?
RT PCR was invented by Kary B. Mullis who is an American Biochemist. He invented RT-PCR in 1985.
The full form of RT-PCR is Reverse transcription - Polymerase Chain Reaction. Is the name itself complex? Not so complex as you think. Before proceeding to RT PCR, it's very important to know what DNA and RNA.
DNA is a double stranded genetic material present in cells of living organisms that passes information to next generations.
RNA is a single stranded genetic material present in most of the viruses in plants and animals. RNA is similar to DNA chemically but RNA has only one strand.
Now first we will dig into the process of Polymerase Chain Reaction (PCR). It involves three processes. They are
1. Denaturation
2. Annealing (Hardening by heating)
3. Elongation.
Denaturation:
The DNA is first separated into single strands. In this we are modifying the structure of DNA.
Annealing (Hardening by heating)
Now small fragment of DNA is combined to the the single stranded DNA. This process usually done by Heating.
Elongation:
Now the DNA fragment that combined with the Single stranded DNA is elongated to make it a double stranded DNA.
After these processes, this DNA is amplified and it involves Cycles. After each cycles the DNA doubles. This is the process of PCR.
Now we will see about the testing process of Covid-19 virus using RT-PCR. In PCR, RNA is not visible.
It can be done only using DNA. As in SARS Cov-2 virus has only RNA, the Covid-19 samples are tested using RT-PCR.
First of all, the sample is collected from areas such as throat, nose and lungs as the virus is supposed to present in mucus from nose and throat and fluid from the lungs.
The collected sample is chemically treated to seperate particles other than DNA and virus( if present).
Now after the RNA is identified, it should be combined (annealed) with small fragment of DNA. After combining, the DNA fragment is elongated using an enzyme called Reverse transcriptase.
Now the single stranded RNA is removed and another fragment of DNA is combined and elongated using the enzyme.
This process continues as a cycle, so that copies of this DNA is created. With each cycle the copy doubles to two, two to four, four to eight and so on. Through this process billion copies of this DNA was created.
A simple video explanation here,
Using these copies of DNA, the scientists test whether the virus is present (positive) or not (negative) with the help of RT-PCR kit.
In India, the resulted copies is subjected to culture and if they are fully cultured then the virus is present, otherwise not. Virus culturing usually takes 24 hours.
That's why in India it takes about two days to get the result. Usually the virus is detected in 35 cycles and if it is detected earlier (less cycles), then it should be understood that the infection is severe.
When a sample is tested positive, usually the process is repeated two to three times for confirmation.
RT-PCR gives almost exact results. That's why it is used as a mandatory test for Covid-19.
Now, IIT Delhi gave license to a Bengaluru based firm named as Genei laboratories to produce to Low cost RT-PCR kits. So India will soon produce it's own RT PCR kit.
There are also some disadvantages in RT-PCR process. They are,
1. It is time consuming
2. Large samples cannot be fed at the same time.
3. Once the plates used can't be reused again.
That's all about the RT-PCR testing process and how Covid-19 samples are tested.
Hope this will be useful to you.
In every blog we decided to introduce new English word and it's usage.
Today's word
Miniscule
This means extremely small.
Usage
The presence RNA is miniscule in the sample.
Let's all learn together and enlighten others.
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