Understanding the Polymerase Chain Reaction (PCR) Technique and Its Applications
Technique PCR that
a. Was used to demonstrate DNA as the genetic material
b. Is used to determine the content of minerals in a soil sample
c. Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
d. Measures the ribosome transfer rate during translation
The Polymerase Chain Reaction (PCR) is a revolutionary molecular biology technique used to amplify specific DNA sequences in vitro. Invented by Kary Mullis in 1985, PCR has become an essential tool for genetic research, medical diagnostics, forensics, and biotechnology. By using short DNA primers and a thermostable DNA polymerase, PCR allows the rapid and accurate replication of target DNA sequences.
Correct Answer: (c) Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
The correct answer is (c) because PCR relies on:
✔️ Short DNA primers – to define the target sequence.
✔️ Thermostable DNA polymerase – to withstand high temperatures during DNA denaturation and extension.
✔️ In vitro conditions – to perform DNA replication outside living cells.
What is PCR?
PCR is a molecular biology technique used to amplify specific DNA sequences from a complex DNA mixture. The technique mimics the natural process of DNA replication but is conducted in a test tube under controlled conditions.
Key Elements of PCR
- Template DNA – The DNA sample that contains the target sequence.
- Primers – Short single-stranded DNA sequences that define the region of DNA to be amplified.
- Thermostable DNA polymerase – Enzyme that synthesizes new DNA strands.
- dNTPs (deoxynucleotide triphosphates) – Building blocks for DNA synthesis.
- Buffer solution – Maintains the optimal reaction environment.
How PCR Works – Step-by-Step Process
1. Denaturation
- The reaction mixture is heated to 94–98°C.
- Double-stranded DNA (dsDNA) separates into two single strands.
2. Annealing
- The mixture is cooled to 50–65°C.
- Primers bind (anneal) to the complementary sequences on the single-stranded DNA.
3. Extension
- Temperature is raised to 72°C.
- DNA polymerase extends the primers, synthesizing new DNA strands.
4. Repetition
- The process is repeated for 20–40 cycles.
- DNA doubles with each cycle, resulting in exponential amplification.
Why PCR is Important in Molecular Biology
✅ 1. High Sensitivity and Specificity
PCR can amplify even trace amounts of DNA with high specificity.
✅ 2. Fast and Efficient
- PCR can produce millions of copies of DNA in a few hours.
- Traditional cloning techniques are time-consuming and labor-intensive.
✅ 3. Flexibility in Targeting DNA Sequences
- PCR can amplify genes, non-coding regions, and even mutated sequences.
- Primers can be designed to target specific sequences.
Types of PCR
1. Conventional PCR
- Basic form of PCR.
- Uses agarose gel electrophoresis to visualize amplified products.
2. Real-Time PCR (qPCR)
- Monitors DNA amplification in real-time using fluorescent dyes.
- Measures gene expression and viral load.
3. Reverse Transcription PCR (RT-PCR)
- Converts RNA into cDNA using reverse transcriptase before PCR.
- Used for gene expression studies and viral detection.
4. Multiplex PCR
- Uses multiple primer sets to amplify different targets simultaneously.
- Saves time and resources.
5. Digital PCR
- Measures absolute DNA quantity by partitioning the sample into individual reactions.
- High sensitivity and accuracy.
Applications of PCR
1. Medical Diagnostics
- Detects infectious diseases like HIV, COVID-19, and hepatitis.
- Identifies genetic mutations linked to inherited disorders.
2. Forensic Science
- DNA fingerprinting for criminal investigations.
- Identifies suspects and establishes biological relationships.
3. Genetic Research
- Cloning and sequencing genes.
- Studying gene expression and mutations.
4. Evolutionary Biology
- Analyzes ancient DNA from fossils and preserved specimens.
- Studies population genetics and phylogenetics.
5. Agriculture and Biotechnology
- Genetically modified organism (GMO) identification.
- Pathogen detection in crops and livestock.
Challenges in PCR
1. Primer Design
- Poor primer design results in non-specific amplification.
- GC content and primer length must be optimized.
2. Contamination
- External DNA contamination leads to false results.
- Strict handling and cleanroom conditions are necessary.
3. PCR Inhibition
- Some biological samples contain inhibitors (e.g., hemoglobin, urea).
- Sample preparation techniques can reduce inhibition.
4. Taq Polymerase Limitations
- Taq polymerase lacks proofreading activity.
- High-fidelity polymerases are used to improve accuracy.
How to Optimize PCR Performance
✔️ Design primers with similar melting temperatures (Tm).
✔️ Maintain proper magnesium ion concentration.
✔️ Reduce cycle number to prevent non-specific amplification.
✔️ Use high-fidelity polymerase for long and accurate amplification.
✔️ Minimize contamination by using separate workspaces for sample preparation and amplification.
Comparison of PCR with Other Techniques
| Technique | Target Molecule | Sensitivity | Amplification | Time Required | Application |
|---|---|---|---|---|---|
| PCR | DNA | High | Yes | Few hours | Diagnostics, Cloning |
| qPCR | DNA/cDNA | High | Yes | Real-time | Gene Expression |
| RT-PCR | RNA | High | Yes | Few hours | Viral Detection |
| Southern Blot | DNA | Moderate | No | 2–3 Days | Gene Mapping |
| Northern Blot | RNA | Moderate | No | 2–3 Days | Gene Expression |
Future of PCR Technology
1. Single-Cell PCR
- Enables amplification from a single cell.
- Useful for cancer research and stem cell biology.
2. Portable PCR Devices
- Handheld PCR machines for field diagnostics.
- Improves response time for disease outbreaks.
3. Digital PCR Advancements
- Higher sensitivity and precision.
- Enables absolute quantification of nucleic acids.
Conclusion
PCR is one of the most powerful and widely used techniques in molecular biology. Its ability to amplify specific DNA sequences with high sensitivity and specificity makes it indispensable in genetic research, medical diagnostics, forensic science, and biotechnology. Understanding the principles of PCR and optimizing reaction conditions are essential for successful DNA amplification.
For expert guidance on molecular biology and PCR techniques, join Let’s Talk Academy — the leading institute for CSIR NET Life Science, IIT JAM, GATE Biotechnology, and DBT JRF preparation.
👉 Learn more about PCR at Let’s Talk Academy.
FAQs
Q1. What is the role of primers in PCR?
Primers define the target sequence and provide a starting point for DNA synthesis.
Q2. Why is Taq polymerase used in PCR?
Taq polymerase is thermostable and remains active at high temperatures.
Q3. What are the advantages of real-time PCR over conventional PCR?
Real-time PCR allows real-time monitoring and quantification of DNA amplification.
This article was written with guidance from Let’s Talk Academy, a top coaching institute for life sciences and biotechnology competitive exams
96 Comments
Pallavi gautam
March 16, 2025Yes sir
Hemlata Meena
March 16, 2025Yes sir 👍
Akshay mahawar
March 16, 2025Done 👍
Suman bhakar
March 16, 2025Done
Priya khandal
March 16, 2025Done sir
yogesh sharma
March 16, 2025Easy Sir
Ujjwal
March 17, 2025Done sir 👍
Nisha
March 17, 2025Done
Arushi
March 17, 2025👍👍
Anmol
March 17, 2025Understood👍🏻
Nisha Meena
March 18, 2025Done
Abhilasha
March 18, 2025Correct ✅
Prami Masih
March 20, 2025Okay sir ji
Parul
March 20, 2025Understood easily. Done sir
Komal Sharma
August 23, 2025PCR is a molecular biology technique used to amplify specific DNA sequences from a complex DNA mixture. The technique mimics the natural process of DNA replication but is conducted in a test tube under controlled conditions so it called in vitro so option C is correct
Sheikh Aleen
August 24, 2025In PCR – uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro.
Neelam Sharma
August 24, 2025PCR tech. Is Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
karishma don
August 24, 2025PCR is in-vitro amplification of a particular dna seq by designing complimentary primes and giving taq polymerase
Meera Gurjar
August 24, 2025C is right
Sakshi yadav
August 24, 2025PCR – uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro.
Mohd juber Ali
August 24, 2025Option c
PCR is the invitro amplification of dna (into cell)
PCR uses short and single strand dna or RNa molecule that binds with complimentary sequence of target dna strand and thermo stable dna polymerase (taq polymerase)
Divya rani
August 24, 2025C is the answer because PCR is the technique in which we used short primers to define the specific DNA sequence and thermostable DNA required at denaturation phase and perform dna amplification outside the living cell inside the tube.
Niti Tanwar
August 24, 2025Right answer is c
Divya Mandhania
August 24, 2025,. PCR is a molecular biology technique used to amplify specific DNA sequences from a complex DNA mixture. The technique mimics the natural process of DNA replication but is conducted in a test tube under controlled conditions so it called in vitro so option C is correct
Ankita Pareek
August 24, 2025In pcr short dna primers, thermostable dna polymerase to amplify specific dna sequence,it is in vitro amplification of dna
Mitali saini
August 24, 2025The correct answer is (c) because PCR relies on:
✔️ Short DNA primers – to define the target sequence.
✔️ Thermostable DNA polymerase – to withstand high temperatures during DNA denaturation and extension.
✔️ In vitro conditions – to perform DNA replication outside living
AKANKSHA RAJPUT
August 24, 2025The correct answer is (c)
Anurag Giri
August 24, 2025Ans c Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
Nilofar Khan
August 24, 2025Correct answer is (c) Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
anjani sharma
August 24, 2025Answer c
PCR – uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro.
Shobha Sharma
August 24, 2025Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequence in vitro
Roopal Sharma
August 24, 2025PCR is a technique uses short dna primer and a thermostable dna polymerase to replicate specific dna sequence in vitro.
Mahima Sharma
August 24, 2025Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
MOHIT AKHAND
August 24, 2025Done sir ✅
Priya dhakad
August 24, 2025In PCR uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro.
Priyanka Choudhary
August 24, 2025C will be right answer Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequence in vitro
Rishita
August 24, 2025Ans .c is the correct answer
Dipti Sharma
August 24, 2025The correct answer is (c) bcz
pcr involves : Short DNA primers ,Thermostable DNA polymerase and In vitro conditions (DNA replication outside living cell)
Khushi Pareek
August 24, 2025C is the correct answer
Shivani Panwar
August 24, 2025Uses short DNA primers and a thermostable DNA polymerase to replication specific DNA sequence in vitro…
Priti khandal
August 24, 2025In pcr use short primer thermos table dna polymerase and in vitro condition
Bharti Yadav
August 24, 2025PCR Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
Alec
August 24, 2025correct ans. is c uses short dna primers and a thermostable dna polymerase to replicate specific dna sequence in vitro.
Avni
August 24, 2025Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
Mansukh Kapoor
August 24, 2025The correct answer is option 3rd
PCR uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
Kajal
August 24, 2025Option c is correct answer use short dna primer and a thermostable dna polymerase ,invito condition to replicate dna ….
Neha Yadav
August 24, 2025Pcr – in vitro Amplification of DNA by using short primer and dna polymerase
Swati Choudhary
August 24, 2025c is correct answer
Anjali
August 25, 2025Ans is c
Surbhi Rajawat
August 25, 2025PCR is a technique used to amplify the given sample of DNA, RNA, or protein by using DNA primers and a thermostable polymerase
Komal Pareek
August 25, 2025PCR is a molecular technique which uses short dna primer and a thermostable polymerase for amplification
Dharmpal Swami
August 25, 2025PCR use a thermostable polymerase and amplification of a short dna sequence
Sonam Saini
August 25, 2025Only c Right
shruti sharma
August 25, 2025Correct answer is (c) Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
Khushi Agarwal
August 25, 2025The correct answer is (c)
because PCR needs Short DNA primers
Thermostable DNA polymerase
In vitro conditions
Soniya Shekhawat
August 25, 2025For PCR used a short DNA primer, thermosable polymerase, occuring outside living cell .
Konika Naval
August 25, 2025Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
Seema
August 25, 2025Option c) is correct.
Pallavi Ghangas
August 25, 2025PCR is in vitro replication technique that uses short primers and thermostable polymers to replicate specific DNA sequence
Deepika Sheoran
August 26, 2025Option C is correct answer
DNA primers and a Thermostable DNA polymerase to replicate specific DNA sequences in vitro.
Muskan singodiya
August 26, 2025Pcr used short dna., in vitro amplification of dna
Shivani
August 26, 2025PCR technique uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro.
Payal Gaur
August 26, 2025PCR technique use short DNA primer and thermostable DNA polymerase sequence to replicate specific DNA In invitro
Minal Sethi
August 26, 2025a specific region of DNA is amplified using thermostable DNA polymerase, primers, Mg+2 ions , all 4 dNTP’s in vitro
Kajal
August 26, 2025(c) Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
Aakanksha Sharma
August 26, 2025PCR use a short dna primer and a thermostable dna polymerase to replicate specific DNA sequence in vitro
Aafreen Khan
August 27, 2025PCR is a technique to u ses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro (outside the cell)
Aman Choudhary
August 27, 2025Option C is correct
PCR is a molecular biology technique used to amplify the specific DNA sequences in vitro
HIMANI FAUJDAR
August 27, 2025Correct answer is (c) In PCR Short DNA primers ,
Thermostabe DNA polymerase and In vitro conditions are used to amplify specific DNA sequences.
Surendra Doodi
August 27, 2025Option C – Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
Rakesh Dhaka
August 27, 2025Correct answer is c
Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
Mohini
August 27, 2025PCR is done using short DNA primers and thermostable Taq polymerase to replicate a specific DNA sequence in vitro.
Vanshika Sharma
August 27, 2025Ans is c
Bhawna Choudhary
August 27, 2025Option C is correct answer
Varsha Tatla
August 27, 2025C will be correct answer because PCR is a molecular biology tech which uses short dna primer n termistable polymerase.it is also dna replication process
Kanica Sunwalka
August 28, 2025use short dna primers and thermostable dna pol to replicate specific dna seq invitro
Khushi Vaishnav
August 28, 2025Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
Tanvi Panwar
August 29, 2025PCR is a technique which uses short primer sequences and a thermostable DNA polymerase which amplifies the DNA in vitro.
Santosh Saini
August 29, 2025PCR tech. Uses short DNA primers and a thermostable DNA polymerase (taq polymerase) to replicate specific DNA sequence in vitro
Simran Saini
August 29, 2025Used short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro.
Aartii sharma
August 29, 2025In PCR we use short DNA primers and a thermostable dna polymerase to replicate specific dna sequence
Pooja Sharma Sharma
August 30, 2025Technique PCR is that uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
Arushi Saini
August 30, 2025Using short DNA primers and thermostable ploymerase to replicate a specific DNA sequence in vitro
Asha Gurzzar
August 30, 2025C is correct, using short dna primer and thermostable polymerase to replicate dna sequence in vitro
Sneha Kumawat
August 30, 2025PCR mein DNA primers aur thermostable taq polymerase ka use karke DNA ko bar bar copy Kiya jata hai
Anisha Beniwal
August 30, 2025uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro.
Neeraj Sharma
August 30, 2025Pcr uses short primers and a thermostable DNA polymerase to replicate specific DNA sequence in vitro
Sakshi Kanwar
August 30, 2025PCR uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA
Yogita
August 31, 2025Short DNA primers
Thermostable DNA polymerase
In vitro conditions
Kirti agarwal
August 31, 2025Short dna primers
Thermostable dna poly.
In vitro condition
Palak Sharma
August 31, 2025PCR uses short DNA primers and DNA Pol. to perform DNA replication outside living cells.
Saniya Jangid
September 1, 2025Done
Shobha Kanwar
September 1, 2025In PCR – uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro.
Himanshi
September 1, 2025Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro
Anisha jakhar
September 4, 2025Option c
Muskan Yadav
September 4, 2025Uses short DNA primers and a thermostable DNA polymerase to replicate specific DNA sequences in vitro.