CBSE Class 12 Biology Chapter 9 Biotechnology — Principles and Processes Worksheet with Answers

Quick Chapter Recap — Biotechnology: Principles and Processes

• Recombinant DNA technology involves cutting DNA with restriction enzymes and joining with ligase.
• PCR amplifies DNA using Taq polymerase, primers, and thermal cycling (denaturation at 94°C, annealing at 50-60°C, extension at 72°C).
• Cloning vectors must have ori (origin of replication), selectable markers, and restriction sites.
• Bioprocess engineering includes upstream and downstream processing for large-scale product purification.
• Gel electrophoresis separates DNA fragments based on size; smaller fragments migrate faster.

Section A — Multiple Choice Questions (MCQs)

• Q1. Which enzyme is called 'molecular scissors' in genetic engineering? (a) DNA ligase (b) DNA polymerase (c) Restriction endonuclease (d) RNA polymerase
• Q2. Taq polymerase used in PCR is obtained from: (a) E. coli (b) Thermus aquaticus (c) Agrobacterium tumefaciens (d) Bacillus subtilis
• Q3. The first restriction endonuclease discovered was: (a) EcoRI (b) HindIII (c) BamHI (d) Hind II
• Q4. A good cloning vector must NOT have: (a) Origin of replication (b) Selectable marker (c) Multiple cloning sites (d) High molecular weight
• Q5. Which of the following is NOT a step in downstream processing? (a) Separation (b) Purification (c) Sterilisation of bioreactor (d) Formulation
• Q6. Insertion of recombinant DNA into host cells is called: (a) Ligation (b) Transformation (c) Translation (d) Transcription

Section B — Fill in the Blanks

• Q7. Restriction enzymes recognise specific __________ sequences in DNA.
• Q8. The enzyme __________ joins DNA fragments by forming phosphodiester bonds.
• Q9. The antibiotic resistance gene in a plasmid acts as a __________ marker.
• Q10. PCR requires a heat-stable enzyme called __________.
• Q11. The technique used to separate DNA fragments by size is __________ electrophoresis.

Section C — True or False Statements

• Q12. All restriction enzymes produce sticky ends after cutting DNA. (True / False)
• Q13. Agrobacterium tumefaciens is used as a cloning vector in animal cells. (True / False)
• Q14. The annealing step in PCR occurs at the highest temperature in the cycle. (True / False)
• Q15. Bioreactors provide optimal conditions of temperature, pH, and oxygen for microbial growth. (True / False)
• Q16. Gel electrophoresis separates DNA based on charge only, not size. (True / False)

Section D — Short Answer Questions (2-3 Marks Each)

• Q17. Define recombinant DNA technology. Why is it called so?
• Q18. Name the three basic steps in genetically modifying an organism.
• Q19. What are palindromic sequences? Give one example with a restriction enzyme.
• Q20. Explain the role of selectable markers in cloning vectors.
• Q21. Differentiate between upstream and downstream processing in bioprocess engineering.

Section E — Long Answer and HOTS Questions (5 Marks Each)

• Q22. Describe the role of restriction endonucleases in recombinant DNA technology. How are they named?
• Q23. Explain the Polymerase Chain Reaction (PCR) with the role of each component and the three main steps in each cycle.
• Q24. What are the key features required in a cloning vector? Discuss with reference to plasmids.

Section F — Case Study Question

Complete Answer Key with Explanations

• A1. (c) Restriction endonuclease — these enzymes cut DNA at specific palindromic sequences.
• A2. (b) Thermus aquaticus — Taq polymerase is heat-stable, isolated from this thermophilic bacterium.
• A3. (d) Hind II — discovered by Hamilton Smith in 1970 from Haemophilus influenzae.
• A4. (d) High molecular weight — vectors should be small for easy manipulation and replication.
• A5. (c) Sterilisation of bioreactor — this is part of upstream processing, not downstream.
• A6. (b) Transformation — process of introducing foreign DNA into competent bacterial cells.
• A7. palindromic (or specific palindromic)
• A8. DNA ligase
• A9. selectable
• A10. Taq polymerase
• A11. gel
• A12. False — Some enzymes like SmaI produce blunt ends; only some produce sticky ends.
• A13. False — Agrobacterium tumefaciens is a natural vector for plant cells, not animal cells.
• A14. False — Annealing occurs at the lowest temperature (~50-60°C); denaturation is at ~94°C.
• A15. True — Bioreactors maintain optimal growth conditions including temperature, pH, oxygen, and nutrient supply.
• A16. False — Gel electrophoresis separates DNA primarily by size; smaller fragments migrate faster toward the anode.
• A17. Recombinant DNA technology is the process of joining DNA molecules from two different sources (often different species) to create a new combination of genes. It is called 'recombinant' because the resulting DNA is a hybrid formed by recombining genetic material from different organisms.
• A18. The three basic steps are: (i) Identification and isolation of the desired gene, (ii) Insertion of the gene into a suitable cloning vector to form recombinant DNA, (iii) Transfer of recombinant DNA into a host cell and selection of genetically modified organisms.
• A19. Palindromic sequences are DNA sequences that read the same on both strands in the 5' to 3' direction. Example: EcoRI recognises the sequence 5'-GAATTC-3' on one strand and 3'-CTTAAG-5' on the complementary strand, which is palindromic.
• A20. Selectable markers are genes in cloning vectors (e.g. antibiotic resistance genes like ampR or tetR) that allow identification and selection of transformed host cells. Only cells that have taken up the recombinant vector survive when grown on media containing the antibiotic, facilitating easy screening.
• A21. Upstream processing involves preparation of the culture system, including formulation of medium, sterilisation, and maintenance of sterile conditions in the bioreactor. Downstream processing involves separation and purification of the desired product after biosynthesis, including filtration, centrifugation, chromatography, and formulation for commercial use.
• A22. Restriction endonucleases are enzymes that cut DNA at specific palindromic recognition sequences, producing either sticky or blunt ends. They are essential tools in recombinant DNA technology for isolating genes and inserting them into vectors. Naming convention: First letter (genus) + first two letters (species) + strain/serotype + order of discovery (Roman numeral). Example: EcoRI from Escherichia coli strain RY13, first enzyme isolated.
• A23. PCR amplifies specific DNA segments in vitro. Components: Template DNA, two primers (oligonucleotides complementary to target DNA ends), Taq polymerase (thermostable DNA polymerase), dNTPs, and buffer. Steps per cycle: (i) Denaturation (~94°C) — DNA strands separate; (ii) Annealing (~50-60°C) — primers bind to complementary sequences; (iii) Extension (~72°C) — Taq polymerase synthesises new DNA strands from primers. After 25-30 cycles, millions of copies are produced exponentially.
• A24. A cloning vector must have: (i) Origin of replication (ori) for autonomous replication inside host, (ii) Selectable marker (e.g. antibiotic resistance gene) to identify transformants, (iii) Cloning sites (recognition sites for restriction enzymes) for inserting foreign DNA, (iv) Small size for easy manipulation. Example: pBR322 plasmid has ori, ampR and tetR markers, and multiple restriction sites.
• Case study answers: (i) EcoRI was used because it cuts DNA at specific palindromic sequences, creating sticky ends that facilitate ligation of the insulin gene into the plasmid. (ii) Ampicillin resistance marker allows selection — only transformed E. coli cells carrying the recombinant plasmid survive on ampicillin-containing medium. (iii) E. coli is easy to culture, grows rapidly, and is well-characterised genetically, making it an ideal host. (iv) The bioreactor provides controlled optimal conditions (temperature, pH, oxygen, nutrients) for large-scale growth of bacteria and maximum insulin production.

How to Use This Worksheet for Maximum Benefit

• Attempt the worksheet in exam-like conditions: 90 minutes, no notes, quiet environment.
• Use the answer key only after completing all sections to ensure honest self-assessment.
• Review NCERT Class 12 Biology Chapter 9 pages for any topic where you scored poorly.
• Focus on terminology: recombinant DNA, restriction enzymes, PCR, cloning vectors, bioprocess engineering.
• Practice drawing labelled diagrams of plasmid vectors and PCR cycle steps for 5-mark questions.
• Revisit incorrect answers after 2-3 days to check retention and conceptual clarity.

Common Mistakes to Avoid in Biotechnology Chapter Questions

• Do not confuse DNA ligase (joins DNA) with restriction enzymes (cut DNA at specific sites).
• Remember PCR temperature sequence: Denaturation (highest ~94°C), Annealing (lowest ~50-60°C), Extension (~72°C).
• Mention all three features of cloning vectors: ori, selectable marker, cloning/restriction sites.
• Differentiate upstream (preparation, sterilisation) from downstream (separation, purification) processing clearly.
• Use correct scientific spelling: palindromic, Thermus aquaticus, recombinant, endonuclease.
• Support long answers with specific examples: EcoRI, pBR322, Taq polymerase, E. coli as host.

Recommended Resources and Further Practice

• NCERT Class 12 Biology Textbook Chapter 9 — in-text and end-of-chapter exercises for foundational practice.
• CBSE Sample Papers 2025 and previous years' board question papers for exam pattern familiarity.
• NCERT Exemplar Class 12 Biology — advanced MCQs and HOTS questions on biotechnology.
• CBSETUTOR.ai — AI tutor with photo upload, unlimited doubt solving, topic notes at ₹999/month, 3-day free trial.
• YouTube channels by experienced CBSE Biology teachers for visual explanations of PCR, recombinant DNA, and bioprocess diagrams.
• Group study and peer discussions to clarify doubts on complex topics like restriction mapping and vector construction.