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Q11(a):
Explain briefly
(a) PCR
Solution :
1. Theoretical Foundation of PCR
Polymerase Chain Reaction (PCR) is a molecular biology technique used to amplify a specific segment of DNA, generating millions of copies from a minute initial sample. This process mimics the biological principle of semi-conservative DNA replication [Per the Watson-Crick model of DNA replication].
2. Essential Requirements
- Template DNA: The target sequence to be amplified.
- Primers: Short, chemically synthesized oligonucleotides (15-30 nucleotides) complementary to the regions flanking the DNA segment.
- Taq Polymerase: A thermostable DNA polymerase isolated from the bacterium Thermus aquaticus, which remains active at high temperatures [By enzyme kinetics property of thermophilic proteins].
- Deoxynucleoside triphosphates (dNTPs): The building blocks for new DNA strands.
3. Sequential Stages of the PCR Cycle
| Stage | Process | Temperature |
|---|---|---|
| Denaturation | The double-stranded DNA template is heated to separate the strands into single strands. | $\approx 94^{\circ}\text{C}$ |
| Annealing | Two sets of primers are allowed to hybridize to their complementary sequences at the $3'$ ends of the separated strands. | $50-65^{\circ}\text{C}$ |
| Extension | Taq polymerase adds nucleotides complementary to the template using dNTPs in the reaction mixture. | $72^{\circ}\text{C}$ |
4. Mathematical Amplification
The PCR process follows an exponential growth pattern defined by the formula:
$N = N_0 \times 2^n$
Where:
- $N$ = Final number of DNA copies.
- $N_0$ = Initial number of DNA templates.
- $n$ = Number of cycles performed.
By repeating the cycle 30-40 times, the reaction generates $2^{30}$ to $2^{40}$ copies of the target DNA, allowing for clinical detection or downstream genetic analysis.
Final Solution: PCR is an in vitro technique of DNA synthesis that utilizes repetitive heating and cooling cycles to exponentially amplify a specific DNA sequence, driven by thermostable Taq DNA polymerase.
More Questions from Class 12 Biology Biotechnology: Principles and Processes EXERCISES
- Q1: Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet).
- Q1: Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet).
- Q2: Make a chart (with diagrammatic representation) showing a restriction enzyme, the substrate DNA on which it acts, the site at which it cuts DNA and the product it produces.
- Q2: Make a chart (with diagrammatic representation) showing a restriction enzyme, the substrate DNA on which it acts, the site at which it cuts DNA and the product it produces.
- Q3: From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know?
- Q3: From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know?
- Q4: What would be the molar concentration of human DNA in a human cell? Consult your teacher.
- Q4: What would be the molar concentration of human DNA in a human cell? Consult your teacher.
- Q5: Do eukaryotic cells have restriction endonucleases? Justify your answer.
- Q5: Do eukaryotic cells have restriction endonucleases? Justify your answer.
- Q6: Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?
- Q6: Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?
- Q7: Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to create a palindromic sequence by following base-pair rules.
- Q7: Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to create a palindromic sequence by following base-pair rules.
- Q8: Can you recall meiosis and indicate at what stage a recombinant DNA is made?
- Q8: Can you recall meiosis and indicate at what stage a recombinant DNA is made?
- Q9: Can you think and answer how a reporter enzyme can be used to monitor transformation of host cells by foreign DNA in addition to a selectable marker?
- Q9: Can you think and answer how a reporter enzyme can be used to monitor transformation of host cells by foreign DNA in addition to a selectable marker?
- Q10(a): Describe briefly the following: (a) Origin of replication
- Q10(a): Describe briefly the following: (a) Origin of replication
- Q10(b): Describe briefly the following: (b) Bioreactors
- Q10(b): Describe briefly the following: (b) Bioreactors
- Q10(c): Describe briefly the following: (c) Downstream processing
- Q10(c): Describe briefly the following: (c) Downstream processing
- Q11(a): Explain briefly (a) PCR
- Q11(b): Explain briefly (b) Restriction enzymes and DNA
- Q11(b): Explain briefly (b) Restriction enzymes and DNA
- Q11(c): Explain briefly (c) Chitinase
- Q11(c): Explain briefly (c) Chitinase
- Q12(a): Discuss with your teacher and find out how to distinguish between (a) Plasmid DNA and Chromosomal DNA
- Q12(a): Discuss with your teacher and find out how to distinguish between (a) Plasmid DNA and Chromosomal DNA
- Q12(b): Discuss with your teacher and find out how to distinguish between (b) RNA and DNA
- Q12(b): Discuss with your teacher and find out how to distinguish between (b) RNA and DNA
- Q12(c): Discuss with your teacher and find out how to distinguish between (c) Exonuclease and Endonuclease
- Q12(c): Discuss with your teacher and find out how to distinguish between (c) Exonuclease and Endonuclease
CBSE Solutions for Class 12 Biology Biotechnology: Principles and Processes
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Evolution
- Human Health and Disease
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
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