UPSC Civil Services Model Paper 8

PCR (Polymerase Chain Reaction)
In this reaction, multiple copies of the gene (or DNA) of interest is synthesized in vitro using two sets of primers (small chemically synthesized oligonucleotides that are complementary to the regions of DNA) and the enzyme DNA polymerase.
Hence, Statement 1 is correct.
The enzyme extends the primers using the nucleotides provided in the reaction and the genomic DNA as a template.
If the process of replication of DNA is repeated many times, the segment of DNA can be amplified approximately a billion times, i.e. 1 billion copies are made.
Such repeated amplification is achieved by the use of a thermostable DNA polymerase (isolated from a bacterium, Thermus aquaticus ), which remain active during the high temperature-induced denaturation of double-stranded DNA.
The amplified fragment if desired can now be used to ligate with a vector for further cloning.
RT-PCR (Real-time Polymerase Chain Reaction) Reverse transcription PCR, or RT-PCR , allows the use of RNA as a template . An additional step allows the detection and amplification of RNA .
The RNA is reverse transcribed into complementary DNA ( cDNA ), using reverse transcriptase.
The quality and purity of the RNA template are essential for the success of RT-PCR.
The first step of RT-PCR is the synthesis of a DNA/RNA hybrid .
Reverse transcriptase also has an RNase H function, which degrades the RNA portion of the hybrid .
The single-stranded DNA molecule is then completed by the DNA-dependent DNA polymerase activity of the reverse transcriptase into cDNA .
The efficiency of the first-strand reaction can affect the amplification process.
The standard PCR procedure is used to amplify the cDNA . The possibility to revert RNA into cDNA by RT-PCR has many advantages.
RNA is single-stranded and very unstable , which makes it difficult to work with.
Most commonly, it serves as the first step in qPCR, which quantifies RNA transcripts in a biological sample.
Real-time RT–PCR is a nuclear-derived method for detecting the presence of specific genetic material in any pathogen , including a virus(COVID-19) . Hence, Statement 2 is correct.