Top 50 CBSE Class 12 Biology MCQs with Answers: CBSE Class 12 Biology Board Exam 2026, scheduled for 27 March 2026 (Friday), is an important exam for students preparing for the final board examination. To support effective revision, this article provides the Top 50 MCQs for CBSE Class 12 Biology, selected from CBSE previous year question papers and based on recent exam patterns.
These CBSE Class 12 Biology MCQs with answers cover important concepts that are frequently asked in pre-boards and boards. Practising these top 50 MCQs will strengthen conceptual clarity, improve accuracy, and boost confidence before the exam. This MCQ set is ideal for last-minute revision and smart preparation to score high in the CBSE Class 12 Biology Pre Board Exam 2026.
Top 50 CBSE Class 12 Biology MCQs
1. Meselson and Stahl proved that DNA replication is
(a) Conservative
(b) Semi-conservative
(c) Dispersive
(d) Random
2. In Meselson–Stahl experiment, bacteria were first grown in medium containing
(a) N¹⁴
(b) N¹⁵
(c) P³²
(d) S³⁵
3. Male honey bees are haploid because they develop from
(a) Fertilised eggs
(b) Unfertilised eggs
(c) Zygote
(d) Spores
4. Which type of evolution is shown by Australian marsupial mouse and placental mouse?
(a) Divergent evolution
(b) Parallel evolution
(c) Convergent evolution
(d) Adaptive radiation
5. Strawberry is an example of fruit formed from
(a) Ovary
(b) Thalamus
(c) Endosperm
(d) Pericarp
6. Surgical method of contraception in human males is called
(a) Tubectomy
(b) Vasectomy
(c) Hysterectomy
(d) Ligation
7. Hormones active during ovulatory phase are
(a) FSH and Estrogen
(b) LH and Estrogen
(c) Estrogen and Progesterone
(d) FSH and Progesterone
8. Which organism fixes atmospheric nitrogen but is not autotrophic?
(a) Nostoc
(b) Anabaena
(c) Oscillatoria
(d) Rhizobium
9. During transcription in prokaryotes, sigma factor helps in
(a) Termination
(b) Elongation
(c) Initiation
(d) Splicing
10. Entry of untreated sewage in a river is indicated by
(a) High dissolved oxygen
(b) Low BOD
(c) Sudden fall in dissolved oxygen
(d) Increase in fish population
11. Expanding human population is shown by
(a) Narrow base pyramid
(b) Bell-shaped pyramid
(c) Broad base pyramid
(d) Inverted pyramid
12. First transgenic product approved for human use was
(a) Insulin
(b) Interferon
(c) α-1 antitrypsin
(d) Growth hormone
13. Directional selection is best explained by
(a) Giraffe neck evolution
(b) Sickle cell anemia
(c) Industrial melanism
(d) Blood groups
14. DNA fingerprinting is based on
(a) VNTRs
(b) mRNA
(c) rRNA
(d) tRNA
15. Number of pollen grains formed from 325 microspore mother cells is
(a) 325
(b) 650
(c) 975
(d) 1300
16. Apomictic embryo formed from nucellus is
(a) Haploid
(b) Diploid
(c) Triploid
(d) Tetraploid
17. Guanine pairs with Cytosine by
(a) One hydrogen bond
(b) Two hydrogen bonds
(c) Three hydrogen bonds
(d) Four hydrogen bonds
18. Chromosomal disorder with short stature and furrowed tongue is
(a) Turner syndrome
(b) Down syndrome
(c) Klinefelter syndrome
(d) Edwards syndrome
19. Pink flowers in Snapdragon show
(a) Codominance
(b) Incomplete dominance
(c) Dominance
(d) Epistasis
20. Dark-winged moths increased after industrialisation due to
(a) Mutation
(b) Migration
(c) Natural selection
(d) Genetic drift
21. Restriction enzyme cuts DNA at
(a) Random sites
(b) Palindromic sites
(c) Coding region
(d) Non-coding region
22. Sticky ends are formed due to
(a) Straight cut
(b) Uneven cut
(c) Circular cut
(d) Blunt cut
23. Bioreactors commonly used are
(a) Airlift type
(b) Stirred tank
(c) Batch type
(d) All of these
24. Bt cotton is resistant to
(a) Aphids
(b) Bollworm
(c) Whitefly
(d) Mosquito
25. Cry genes are obtained from
(a) E. coli
(b) Bacillus thuringiensis
(c) Agrobacterium
(d) Rhizobium
26. HIV attacks
(a) RBCs
(b) Neurons
(c) B-cells
(d) T-helper cells
27. Interferons are
(a) Antibiotics
(b) Vaccines
(c) Antiviral proteins
(d) Hormones
28. Vaccine prepared from killed pathogen is
(a) Live vaccine
(b) Subunit vaccine
(c) Inactivated vaccine
(d) DNA vaccine
29. Secondary productivity refers to
(a) Plant biomass
(b) Animal biomass
(c) Decomposer biomass
(d) Producer biomass
30. Pyramid of energy is always
(a) Inverted
(b) Upright
(c) Spindle-shaped
(d) Irregular
31. Ex-situ conservation includes
(a) Wildlife sanctuary
(b) National park
(c) Zoological park
(d) Biosphere reserve
32. Hot spots are regions with
(a) Low biodiversity
(b) High endemism
(c) High pollution
(d) Cold climate
33. Anther contains
(a) Ovules
(b) Microsporangia
(c) Megasporangia
(d) Endosperm
34. Double fertilisation occurs in
(a) Gymnosperms
(b) Algae
(c) Angiosperms
(d) Bryophytes
35. Fusion of male gamete with egg is called
(a) Syngamy
(b) Triple fusion
(c) Pollination
(d) Germination
36. Seed without fertilisation is called
(a) Parthenocarpy
(b) Apomixis
(c) Polyembryony
(d) Hybridisation
37. PCR stands for
(a) Protein chain reaction
(b) Polymerase chain reaction
(c) Peptide chain reaction
(d) Primer chain reaction
38. Enzyme used in PCR is
(a) DNA ligase
(b) RNA polymerase
(c) Taq polymerase
(d) Restriction enzyme
39. AIDS is caused by
(a) DNA virus
(b) Bacteria
(c) RNA virus
(d) Protozoa
40. Female Anopheles mosquito transmits
(a) Dengue
(b) Malaria
(c) Typhoid
(d) Cholera
41. Fertilisation in Plasmodium occurs in
(a) Human liver
(b) Human RBC
(c) Mosquito gut
(d) Mosquito salivary gland
42. Sporogony occurs in
(a) Human
(b) Mosquito
(c) Both
(d) None
43. Detritivores feed on
(a) Producers
(b) Consumers
(c) Detritus
(d) Parasites
44. Maximum energy is available at
(a) Tertiary consumers
(b) Secondary consumers
(c) Primary consumers
(d) Producers
45. Lichens indicate pollution because they are sensitive to
(a) CO₂
(b) SO₂
(c) O₂
(d) NO₂
46. Mutualism is seen in
(a) Lichen
(b) Tapeworm
(c) Cuscuta
(d) Plasmodium
47. Gene responsible for colour blindness is
(a) Autosomal dominant
(b) Autosomal recessive
(c) X-linked recessive
(d) Y-linked
48. Chromosome number in human secondary spermatocyte is
(a) 44
(b) 46
(c) 23
(d) 22
49. Insulin was first produced by genetic engineering in
(a) Plants
(b) Animals
(c) Bacteria
(d) Fungi
50. Biodiversity is highest in
(a) Temperate forests
(b) Deserts
(c) Tundra
(d) Tropical rainforests
Top 50 CBSE Class 12 Biology MCQs with Answers
| Question No. | Correct Answer |
| 1 | (b) |
| 2 | (b) |
| 3 | (b) |
| 4 | (c) |
| 5 | (b) |
| 6 | (b) |
| 7 | (b) |
| 8 | (d) |
| 9 | (c) |
| 10 | (c) |
| 11 | (c) |
| 12 | (c) |
| 13 | (a) |
| 14 | (a) |
| 15 | (d) |
| 16 | (b) |
| 17 | (c) |
| 18 | (b) |
| 19 | (b) |
| 20 | (c) |
| 21 | (b) |
| 22 | (b) |
| 23 | (d) |
| 24 | (b) |
| 25 | (b) |
| 26 | (d) |
| 27 | (c) |
| 28 | (c) |
| 29 | (b) |
| 30 | (b) |
| 31 | (c) |
| 32 | (b) |
| 33 | (b) |
| 34 | (c) |
| 35 | (a) |
| 36 | (b) |
| 37 | (b) |
| 38 | (c) |
| 39 | (c) |
| 40 | (b) |
| 41 | (c) |
| 42 | (b) |
| 43 | (c) |
| 44 | (d) |
| 45 | (b) |
| 46 | (a) |
| 47 | (c) |
| 48 | (c) |
| 49 | (c) |
| 50 | (d) |
Regular practice of these CBSE Class 12 Biology MCQs will improve accuracy, speed, and confidence before the exam. Use this MCQ set for smart revision to perform well in the CBSE Class 12 Biology Pre Board Exam 2026.
Also check:
Comments
All Comments (0)
Join the conversation