Biotechnology Principles and Processes — Class 12 Biology NCERT Solutions (Free)
Free step-by-step NCERT solutions for Class 12 Biology chapter "Biotechnology Principles and Processes" — 8 important questions with detailed answers for CBSE board exam preparation.
TL;DR: Free step-by-step NCERT solutions for Class 12 Biology chapter "Biotechnology Principles and Processes" — 8 important questions with detailed answers…
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NCERT Solutions for Class 12 Biology — Biotechnology Principles and Processes. Step-by-step answers to all 8 textbook questions from this chapter, written for CBSE board preparation and free to use.
Biotechnology Principles and Processes — All 8 Questions Solved
Q1. Define biotechnology.
Biotechnology is the technology that uses living cells, organisms, or their components (enzymes, DNA, proteins) to obtain useful products and services for human welfare. It integrates biology with engineering, chemistry, and medicine to develop new technologies and solve problems in agriculture, medicine, industry, and environment.
Q2. What is genetic engineering? Explain its basic steps.
Genetic engineering is the process of introducing desired genes into an organism's genome to alter its genetic makeup and create new traits. It involves manipulation of DNA to produce organisms with new characteristics.
BASIC STEPS:
1. IDENTIFICATION OF DESIRED GENE:
- Identify the trait or protein to be introduced
- Locate the source organism containing the desired gene
- Examples: Insulin gene from human, Bt toxin gene from Bacillus thuringiensis
2. GENE ISOLATION:
- Extract DNA from source organism
- Use restriction enzymes to cut DNA at specific sequences
- Isolate the desired gene segment
- Use techniques like PCR to amplify the gene
3. INSERTION INTO VECTOR:
- Use a vector (plasmid, phage, or cosmid) to carry the gene
- Restriction enzyme cuts vector DNA at compatible sites
- Gene is ligated (joined) into vector using DNA ligase
- Creates recombinant DNA
4. INTRODUCTION INTO HOST CELL:
- Recombinant DNA transferred into host cell (bacterium, plant, or animal)
- Methods: Transformation, transfection, microinjection
- Vector carries foreign DNA into cell nucleus
5. EXPRESSION AND SCREENING:
- Foreign gene expresses in host cell producing desired protein
- Identify and select transformed cells
- Grow transformed cells/organisms
6. EVALUATION:
- Test for desired traits
- Ensure stability of new characteristics
- Check for any undesirable effects
Q3. What is a restriction enzyme? How is it used in genetic engineering?
Restriction enzymes (restriction endonucleases) are bacterial proteins that recognize and cut DNA at specific sequences called recognition sites. They are essential tools in genetic engineering.
CHARACTERISTICS:
- Recognize specific palindromic DNA sequences (4-8 base pairs)
- Cut DNA double strand at specific positions
- Produce sticky ends (cohesive) or blunt ends
- Work like 'molecular scissors'
- Each enzyme cuts at different recognition sequences
USES IN GENETIC ENGINEERING:
1. CUTTING DNA:
- Isolate desired gene from source DNA
- Cut recombinant plasmids to insert foreign genes
- Produces compatible sticky ends for gene insertion
2. CREATING RESTRICTION MAPS:
- Determine locations of restriction sites on DNA
- Help in gene mapping and DNA analysis
- Identify genetic variations
3. IDENTIFYING RECOMBINANTS:
- Distinguish between recombinant and non-recombinant plasmids
- Screen transformed colonies
- Use insertional inactivation
4. FINGERPRINTING:
- Create DNA fingerprints for identification
- Used in forensics and paternity testing
- Compare genetic variations between individuals
EXAMPLE:
- EcoRI cuts at GAATTC sequence producing sticky ends
- BamHI cuts at GGATCC sequence
- PstI cuts at CTGCAG sequence
Q4. Explain the structure and function of a plasmid as a vector in genetic engineering.
A plasmid is a small, circular, double-stranded DNA molecule that exists independently of the bacterial chromosome. It is widely used as a vector in genetic engineering.
STRUCTURE:
- Circular DNA (usually 1-10 kb in size)
- Double-stranded (dsDNA)
- Exists separately from chromosomal DNA in bacterial cells
- Contains about 5,000-30,000 base pairs
- Replicates autonomously
KEY FEATURES FOR VECTOR USE:
1. ORIGIN OF REPLICATION (ori):
- DNA sequence where replication begins
- Allows plasmid to replicate independently in host cell
- Essential for maintaining plasmid in host
2. RESTRICTION SITES:
- Multiple cloning sites (MCS) with various restriction enzyme recognition sites
- Allows easy insertion of foreign DNA
- Located in non-essential genes
3. SELECTABLE MARKER GENES:
- Antibiotic resistance genes (ampicillin, tetracycline)
- Allows identification of transformed cells
- Only transformed cells survive antibiotic selection
4. REPORTER GENES:
- lacZ gene for insertional inactivation
- Identifies recombinant vs non-recombinant plasmids
- Produces colored colonies on indicator medium
FUNCTIONS:
1. Carries foreign genes into host cells
2. Ensures replication of foreign DNA in host
3. Enables expression of introduced genes
4. Allows identification of successfully transformed cells
5. Maintains genetic stability
ADVANTAGES:
- Easy to manipulate and introduce into cells
- Replicates efficiently
- No integration into chromosome needed
- High copy number (many plasmids per cell)
- Stable maintenance in host cells
Q5. What is PCR (Polymerase Chain Reaction)? Describe its three main steps.
PCR (Polymerase Chain Reaction) is an in vitro technique that amplifies specific DNA sequences exponentially, producing millions of copies from a single DNA molecule. It is one of the most important tools in biotechnology and genetic engineering.
THREE MAIN STEPS (One Cycle):
STEP 1 - DENATURATION (94-95°C, 15-30 seconds):
- Double-stranded DNA is heated to separate into single strands
- Hydrogen bonds between complementary bases break
- Produces single-stranded template DNA
- Temperature must be high enough to denature but not damage Taq polymerase
STEP 2 - ANNEALING (50-65°C, 20-40 seconds):
- Temperature is lowered to allow primers to bind
- Primers (short DNA sequences, 18-25 bp) attach to complementary sequences on single-stranded template
- One primer binds to forward strand, one to reverse strand
- Primers are located at the boundaries of the target sequence
- Temperature depends on primer Tm (melting temperature)
STEP 3 - EXTENSION (72°C, 1-2 minutes):
- Temperature is raised to optimal for Taq DNA polymerase (72°C)
- Taq polymerase (heat-stable enzyme from Thermus aquaticus) extends from primers
- Polymerase adds nucleotides (dNTPs) in 5' to 3' direction
- Synthesizes new DNA strand complementary to template
- Produces double-stranded DNA identical to target
REPETITION:
- Cycle repeated 25-35 times
- Each cycle doubles DNA amount
- Produces 2^n copies (n = number of cycles)
- After 30 cycles: ~1 billion copies from single DNA molecule
REQUIREMENTS:
- DNA template containing target sequence
- Two primers (forward and reverse)
- Taq DNA polymerase (heat-stable)
- dNTPs (dATP, dCTP, dGTP, dTTP)
- Buffer solution
- Thermal cycler machine
Q6. What is DNA ligase? Explain its role in recombinant DNA formation.
DNA ligase is an enzyme that catalyzes the formation of phosphodiester bonds between DNA fragments. It is essential for joining DNA pieces in genetic engineering.
FUNCTION:
- Joins 3' hydroxyl (OH) group of one DNA strand to 5' phosphate group of another
- Seals nicks (breaks) in DNA sugar-phosphate backbone
- Catalyzes formation of covalent phosphodiester bonds
- Uses ATP energy to form these bonds
ROLE IN RECOMBINANT DNA FORMATION:
1. JOINING INSERT AND VECTOR:
- Restriction enzyme cuts both foreign DNA (insert) and vector plasmid
- Creates compatible sticky ends (cohesive ends)
- DNA ligase joins insert into vector
- Forms circular recombinant plasmid
- Seals breaks in DNA backbone
2. ENSURING STABILITY:
- Phosphodiester bonds created by ligase make joined DNA stable
- Prevents recombinant DNA from separating
- Allows recombinant DNA to replicate in host cells
3. MULTIPLE INSERTIONS:
- If multiple inserts are joined, ligase connects all pieces
- Creates stable recombinant molecules
TYPES OF DNA LIGASE:
1. T4 DNA LIGASE:
- From bacteriophage T4
- Most commonly used in molecular cloning
- Works with sticky and blunt ends
- Requires ATP as energy source
- Temperature: 16°C to room temperature
2. E. COLI DNA LIGASE:
- From Escherichia coli bacteria
- Works mainly with sticky ends
- Less efficient than T4 ligase
- Uses NAD+ as cofactor
CONDITIONS FOR OPTIMAL ACTIVITY:
- pH: 7-8
- Temperature: 16-37°C depending on source
- Presence of ATP (for T4) or NAD+ (for E. coli)
- Presence of Mg2+ ions
- Appropriate DNA concentration
Q7. Explain the process of transformation and transfection used to introduce foreign DNA into cells.
Transformation and transfection are methods to introduce recombinant DNA into host cells. Both are crucial techniques in genetic engineering.
TRANSFORMATION (For Bacteria):
DEFINITION:
- Uptake of naked DNA by competent bacterial cells
- Direct incorporation of foreign DNA into bacterial genome or plasmid
- Occurs naturally in some bacteria and artificially induced in lab
PROCESS:
1. Prepare competent cells: Bacteria treated to increase DNA permeability
- Chemical method: Calcium chloride (CaCl2) treatment makes cell wall permeable
- Temperature shock: Heat shock briefly activates DNA uptake (42°C for 60-90 seconds)
2. Introduce recombinant DNA
3. Allow recovery in growth medium without selection
4. Plate on selective medium (antibiotic-containing agar)
5. Select and identify transformed colonies
MECHANISM:
- CaCl2 makes bacterial cell membrane permeable
- DNA passes through cell wall and membrane
- Enters cytoplasm
- May integrate with chromosome or persist as plasmid
CHARACTERISTICS:
- Efficiency: 0.01-10% of cells take up DNA
- Simple and cost-effective
- Works well with plasmids
- Used primarily in bacteria (especially E. coli)
TRANSFECTION (For Animal/Plant Cells):
DEFINITION:
- Introduction of foreign DNA into animal or plant cells
- More complex than bacterial transformation
- Less efficient but essential for eukaryotic engineering
METHODS:
1. MICROINJECTION:
- Direct injection of DNA into cell nucleus using fine micropipette
- Uses micromanipulator for precision
- Efficiency: 5-50%
- Labor-intensive and requires skill
- Used for: Large cells, precise insertion, important experiments
2. ELECTROPORATION:
- Electric pulses create temporary pores in cell membrane
- DNA passes through pores into cell
- Efficiency: 10-80%
- Works for bacteria and eukaryotes
- Used for: Fungi, plant protoplasts, mammalian cells
3. LIPOSOME-MEDIATED TRANSFECTION (LIPOFECTION):
- DNA packaged in liposomes (lipid vesicles)
- Liposomes fuse with cell membrane
- DNA released into cytoplasm
- Efficiency: 5-50%
- Gentler method, less toxic
- Used for: Cell lines, primary cells
4. MICROPARTICLE/GUN METHOD:
- DNA coated on gold or tungsten microparticles
- Shot into cells at high velocity
- Particles penetrate cell membrane
- Efficiency: 1-30%
- Used for: Plant cells, tissues
5. AGROBACTERIUM-MEDIATED TRANSFECTION:
- Uses bacterium Agrobacterium tumefaciens
- Naturally transfers DNA into plant cells
- Ti plasmid carries desired genes
- Efficiency: 10-70%
- Most common for plant genetic engineering
COMPARISON:
- Transformation: Bacteria, simple, efficient, inexpensive
- Transfection: Eukaryotes, complex, less efficient, expensive methods
Q8. What is insertional inactivation? How is it used to identify recombinant clones?
Insertional inactivation is a technique used to identify recombinant clones (cells containing recombinant DNA) from non-recombinant clones. It is based on disruption of a reporter gene.
PRINCIPLE:
- A reporter gene (usually lacZ) is inserted into the plasmid vector
- Multiple cloning site (MCS) is located within the lacZ gene
- When foreign DNA is inserted into MCS, lacZ gene is interrupted/inactivated
- Recombinant plasmids have non-functional lacZ
- Non-recombinant plasmids have functional lacZ
PROCESS:
1. PLASMID CONSTRUCTION:
- Plasmid contains lacZ gene and antibiotic resistance gene
- MCS is positioned within lacZ coding sequence
- Restriction enzyme cuts at MCS site
2. INSERTION OF FOREIGN DNA:
- Foreign DNA inserted at MCS
- Disrupts lacZ gene sequence
- Gene no longer produces functional protein
3. TRANSFORMATION:
- Recombinant and non-recombinant plasmids introduced into bacteria
- Bacteria plated on selection medium (antibiotic agar)
- Only transformed cells survive (antibiotic resistance)
4. SCREENING ON INDICATOR MEDIUM:
- Colonies grown on X-gal and IPTG containing agar
- IPTG induces expression of remaining lacZ gene
- X-gal (substrate) is cleaved by β-galactosidase enzyme (lacZ product)
- Produces blue color
IDENTIFICATION:
BLUE COLONIES:
- lacZ gene is intact and functional
- Produce functional β-galactosidase enzyme
- Cleave X-gal to produce blue pigment
- Contain NON-RECOMBINANT plasmids (self-ligated)
WHITE COLONIES:
- lacZ gene is disrupted/inactivated
- Cannot produce functional β-galactosidase enzyme
- X-gal is not cleaved, remains colorless
- Contain RECOMBINANT plasmids (with foreign DNA insert)
- These are the desired clones
ADVANTAGES:
- Simple visual identification
- No need for complex molecular analysis
- Rapid screening of colonies
- Cost-effective
- High success rate
LIMITATIONS:
- Only works if foreign DNA insertion inactivates lacZ
- Doesn't provide information about gene function
- Some inserts may not completely inactivate lacZ
Biotechnology Principles and Processes — Practice MCQs with Answers
Attempt these 20 multiple-choice questions after working through the solutions above. Each carries the correct option and the reasoning behind it, so a wrong answer tells you which idea to revisit.
MCQ 1. What is the primary focus of 'modern biotechnology' as defined by the European Federation of Biotechnology (EFB)?
- A. Use of microorganisms for industrial products.
- B. Use of living organisms to create new products.
- C. Integration of natural science and organisms, cells, parts thereof, and molecular analogues for products and services.
- D. Genetic modification of plants and animals.
Answer: C. Integration of natural science and organisms, cells, parts thereof, and molecular analogues for products and services. — The EFB definition emphasizes the integration of natural science and engineering with biological systems to produce goods and services for human welfare.
MCQ 2. Restriction enzymes belong to which class of enzymes?
- A. Ligases
- B. Nucleases
- C. Polymerases
- D. Proteases
Answer: B. Nucleases — Restriction enzymes are a type of nuclease that cleave the phosphodiester bonds within a polynucleotide chain. Specifically, they are endonucleases because they cut within the DNA molecule, not just at the ends.
MCQ 3. In the name 'EcoRI', what does the letter 'R' signify?
- A. The Roman numeral indicating the order of discovery.
- B. The genus of the bacterium from which the enzyme was isolated.
- C. The strain of the bacterium from which the enzyme was isolated.
- D. The species of the bacterium from which the enzyme was isolated.
Answer: C. The strain of the bacterium from which the enzyme was isolated. — In the nomenclature of restriction enzymes, the first letter comes from the genus, the next two letters from the species, and the fourth letter (like 'R') indicates the strain of the prokaryotic cell from which the enzyme was isolated.
MCQ 4. Which of the following is a crucial feature in a cloning vector that helps in identifying and eliminating non-transformants?
- A. Origin of replication (ori)
- B. Restriction site
- C. Selectable marker
- D. Multiple Cloning Site (MCS)
Answer: C. Selectable marker — A selectable marker, such as genes for antibiotic resistance (e.g., ampicillin resistance), allows for the selective growth of transformants and the elimination of non-transformants.
MCQ 5. Which enzyme is primarily used in Polymerase Chain Reaction (PCR) for amplifying DNA?
- A. DNA ligase
- B. Reverse transcriptase
- C. Taq polymerase
- D. Restriction endonuclease
Answer: C. Taq polymerase — Taq polymerase is a thermostable DNA polymerase isolated from *Thermus aquaticus*. Its ability to withstand high temperatures during denaturation makes it ideal for PCR.
MCQ 6. When two different DNA fragments are cut by the same restriction enzyme, they can be joined together by DNA ligase. This is primarily because:
- A. They acquire blunt ends, which are easy to join.
- B. They acquire sticky ends that are complementary to each other.
- C. DNA ligase can join any two DNA fragments regardless of their ends.
- D. Restriction enzymes always produce identical fragments suitable for ligation.
Answer: B. They acquire sticky ends that are complementary to each other. — Most restriction enzymes produce sticky ends (overhangs) that are complementary. When two DNA fragments are cut with the same enzyme, their sticky ends can anneal, forming temporary hydrogen bonds, which are then sealed by DNA ligase.
MCQ 7. What method is commonly used to make bacterial cells competent to take up foreign DNA?
- A. Treatment with high concentration of NaCl followed by heat shock.
- B. Treatment with divalent cations like calcium, followed by heat shock.
- C. Treatment with detergents to disrupt the cell membrane.
- D. Treatment with enzymes to digest the cell wall.
Answer: B. Treatment with divalent cations like calcium, followed by heat shock. — Treating bacterial cells with a specific concentration of a divalent cation like calcium (CaCl2) makes the cell wall permeable to DNA, followed by heat shock to facilitate DNA entry.
MCQ 8. The 'ori' site in a cloning vector is responsible for:
- A. Providing resistance to antibiotics.
- B. Initiating the replication of the inserted DNA.
- C. Binding of restriction enzymes.
- D. Facilitating the entry of DNA into the host cell.
Answer: B. Initiating the replication of the inserted DNA. — The 'ori' or origin of replication is a specific DNA sequence in a vector where replication initiates. Any piece of DNA linked to this sequence can be made to replicate within the host cell.
MCQ 9. In a cloning experiment using pBR322 vector, a foreign DNA fragment is ligated into the *BamHI* site. The recombinant plasmid would result in:
- A. Loss of tetracycline resistance.
- B. Loss of ampicillin resistance.
- C. Retention of both tetracycline and ampicillin resistance.
- D. Resistance to both tetracycline and ampicillin would be enhanced.
Answer: A. Loss of tetracycline resistance. — The *BamHI* site in pBR322 is located within the tetracycline resistance gene. Ligation of foreign DNA into this site causes insertional inactivation of the gene, leading to the loss of tetracycline resistance.
MCQ 10. What is the final step in the biotechnological process after biosynthesis of the desired product?
- A. Gene cloning
- B. Bioreactor cultivation
- C. Downstream processing
- D. Transformation
Answer: C. Downstream processing — Downstream processing involves separation and purification of the desired product, followed by formulation and quality control, making it the final step after the biosynthetic stage in a bioreactor.
MCQ 11. Which characteristic best describes the recognition sequence for most restriction enzymes?
- A. A sequence rich in AT base pairs.
- B. A sequence that reads the same on both strands when read in the 5' to 3' direction.
- C. A sequence that is recognized only in the coding region of a gene.
- D. A sequence that is always 10-12 base pairs long.
Answer: B. A sequence that reads the same on both strands when read in the 5' to 3' direction. — Restriction enzymes typically recognize palindromic sequences, which read the same on both strands when the orientation of reading is kept the same (e.g., 5'-GAATTC-3' and 3'-CTTAAG-5').
MCQ 12. Arrange the following steps of gene cloning in the correct sequence: I. Isolation of the desired gene. II. Ligation of DNA fragment into a vector. III. Introduction of recombinant DNA into a host cell. IV. Amplification of the gene of interest. V. Obtaining the foreign gene product.
- A. I, II, IV, III, V
- B. I, IV, II, III, V
- C. I, II, III, IV, V
- D. II, I, IV, III, V
Answer: B. I, IV, II, III, V — The correct sequence involves first isolating the gene, then amplifying it (e.g., by PCR), ligating it into a vector, introducing the recombinant vector into a host, and finally expressing and obtaining the product.
MCQ 13. What is the primary purpose of agarose gel electrophoresis in biotechnology?
- A. Synthesize DNA fragments.
- B. Amplify DNA sequences.
- C. Separate DNA fragments based on their size.
- D. Insert DNA into a vector.
Answer: C. Separate DNA fragments based on their size. — Agarose gel electrophoresis is a technique used to separate DNA fragments based on their size and charge, with smaller fragments moving faster through the gel matrix.
MCQ 14. Which of the following best defines a plasmid in the context of bacterial genetics and biotechnology?
- A. The main chromosomal DNA of a bacterium.
- B. A small, circular, extrachromosomal DNA molecule capable of autonomous replication.
- C. A linear DNA molecule found in the nucleus of eukaryotic cells.
- D. A type of viral genome integrated into the host chromosome.
Answer: B. A small, circular, extrachromosomal DNA molecule capable of autonomous replication. — Plasmids are distinct from the main bacterial chromosome, are circular, exist outside the chromosome, and can replicate independently, making them ideal as cloning vectors.
MCQ 15. A stirred-tank bioreactor is preferred over a shake flask for industrial production of recombinant proteins primarily because:
- A. It uses less raw material.
- B. It provides a uniform environment with optimal growth conditions.
- C. It allows for faster DNA transformation.
- D. It helps in isolating the DNA more efficiently.
Answer: B. It provides a uniform environment with optimal growth conditions. — Stirred-tank bioreactors offer advantages like continuous agitation for uniform mixing of contents, better aeration, temperature control, and pH control, which are crucial for optimal growth and product yield on an industrial scale.
MCQ 16. From which source is the DNA containing the 'gene of interest' typically isolated?
- A. Host cell
- B. Vector
- C. Donor organism/cell
- D. Restriction enzyme
Answer: C. Donor organism/cell — The gene of interest, which is to be cloned and expressed, originates from a donor organism or cell that naturally possesses that specific gene.
MCQ 17. After lysing cells and removing proteins and RNA, how is purified DNA typically precipitated from the solution?
- A. By adding proteases.
- B. By chilling the solution.
- C. By adding chilled ethanol.
- D. By filtering through a fine mesh.
Answer: C. By adding chilled ethanol. — Chilled ethanol is added to the DNA solution, causing the DNA to precipitate out as fine threads that can then be spooled out.
MCQ 18. If a circular plasmid DNA has two recognition sites for a particular restriction enzyme, how many DNA fragments will be generated upon digestion with that enzyme?
- A. One
- B. Two
- C. Three
- D. Four
Answer: B. Two — For a circular DNA molecule, each restriction site corresponds to a cut. If there are 'n' restriction sites, 'n' fragments will be produced. So, two sites will produce two fragments.
MCQ 19. The ultimate aim of gene cloning is to:
- A. Isolate DNA fragments.
- B. Amplify a specific gene sequence.
- C. Introduce genetic variations.
- D. Destroy unwanted genes.
Answer: B. Amplify a specific gene sequence. — Gene cloning is fundamentally about making multiple identical copies of a specific gene or DNA segment, hence amplifying it.
MCQ 20. What is the primary function of DNA ligase in recombinant DNA technology?
- A. To cut DNA at specific recognition sites.
- B. To synthesize new DNA strands.
- C. To join two DNA fragments by forming phosphodiester bonds.
- D. To separate DNA strands during replication.
Answer: C. To join two DNA fragments by forming phosphodiester bonds. — DNA ligase is often referred to as 'molecular glue' because it forms phosphodiester bonds to join DNA fragments, creating a continuous recombinant DNA molecule.
How to Use These Solutions
Attempt each question yourself first and only then compare with the worked answer. Marks in the CBSE board exam are awarded for the METHOD as much as the final result, so reproduce the steps rather than memorising the last line. Where a solution states a law, a formula or a definition, learn that wording — examiners look for it.
Related practice for this chapter: chapter MCQs, previous-year questions, revision notes and sample papers.