Class 12 Biology Sample Paper – 2026

Time: 3 Hours
Maximum Marks: 70

Section A – MCQs (1×16 = 16 Marks)

Choose the correct option:

1. The enzyme responsible for joining Okazaki fragments is:
   a) DNA polymerase
   b) Ligase
   c) Helicase
   d) Primase

2. The functional unit of kidney is:
   a) Neuron
   b) Nephron
   c) Alveolus
   d) Glomerulus

3. Which hormone regulates blood sugar level?
   a) Thyroxine
   b) Insulin
   c) Adrenaline
   d) Estrogen

4. Double fertilization occurs in:
   a) Gymnosperms
   b) Pteridophytes
   c) Angiosperms
   d) Bryophytes

5. BT cotton is resistant to:
   a) Fungi
   b) Bacteria
   c) Insects
   d) Viruses

6. The “Father of Green Revolution in India” is:
   a) Norman Borlaug
   b) M.S. Swaminathan
   c) Watson
   d) Mendel

7–16. (Add similar MCQs from Genetics, Evolution, Ecology, Reproduction, Biotechnology etc.)

Section B – Very Short Answer (2×5 = 10 Marks)

1. Define transcription.

2. What is ecological succession?

3. Name two contraceptive methods.

4. What are homologous organs?

5. Define biodiversity.

Section C – Short Answer (3×7 = 21 Marks)

1. Explain the structure of DNA with diagram.

2. Describe menstrual cycle phases.

3. What is PCR? Explain its steps.

4. Write short note on Hardy–Weinberg principle.

5. Explain nitrogen cycle.

6. What are plant growth regulators?

7. Describe lac operon model.

Section D – Long Answer (4×3 = 12 Marks)

1. Explain human heart structure and double circulation.

2. Describe inheritance of blood groups.

3. Explain in vitro fertilization (IVF).

Section E – Case Study Based (5×2 = 10 Marks)

Case Study 1: AIDS

HIV attacks immune system and reduces CD4 cells.

a) Name the virus causing AIDS.
b) How is HIV transmitted?
c) Why does immunity decrease?
d) Name one prevention method.
e) Expand ART.

✅ ANSWER KEY

Section A:

1. b) Ligase

2. b) Nephron

3. b) Insulin

4. c) Angiosperms

5. c) Insects

6. b) M.S. Swaminathan

Section B:

1. Transcription is synthesis of RNA from DNA template.

2. Gradual change in species composition in ecosystem over time.

3. Condoms, Oral pills.

4. Organs with same origin but different functions.

5. Variety of living organisms in a region.

Section C (Brief Points):

1. DNA: Double helix, sugar-phosphate backbone, A-T & G-C pairing.

2. Menstrual phases: Menstrual, Follicular, Ovulation, Luteal.

3. PCR Steps: Denaturation, Annealing, Extension.

4. p² + 2pq + q² = 1

5. Nitrogen fixation → Nitrification → Assimilation → Denitrification.

6. Auxins, Gibberellins, Cytokinins, Ethylene, ABA.

7. Gene regulation in bacteria (inducible system).

Section D:

(Explain in 5–6 detailed points each)

Section E:

1. HIV

2. Blood transfusion, unprotected sex, mother-to-child

3. CD4 cells destroyed

4. Safe sex

5. Anti-Retroviral Therapy

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