CBSE Class 12 Biology - 25 PYQ MCQ Quiz with answers

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CBSE Class 12 Biology – 25 PYQ-Based MCQ Quiz

25 board-exam style Biology questions based on recurring CBSE previous-year question themes.

Select one answer for each question and click Submit Quiz.

Note: These are PYQ-based/paraphrased practice questions, not verbatim CBSE paper questions. Topics follow the CBSE Class XII Biology curriculum and recent question-paper patterns.

Sexual Reproduction in Flowering Plants

1. In a flowering plant, the pollen grain develops from a:

(A) Megaspore(B) Microspore(C) Ovule(D) Zygote

Correct Answer: (B) Microspore

Sexual Reproduction in Flowering Plants

2. Double fertilisation in angiosperms results in the formation of:

(A) Two zygotes(B) Zygote and primary endosperm nucleus(C) Two embryos(D) Only endosperm

Correct Answer: (B) Zygote and primary endosperm nucleus

Sexual Reproduction in Flowering Plants

3. The mature embryo sac of a typical angiosperm contains:

(A) 3 cells and 3 nuclei(B) 5 cells and 5 nuclei(C) 7 cells and 8 nuclei(D) 8 cells and 8 nuclei

Correct Answer: (C) 7 cells and 8 nuclei

Human Reproduction

4. Which hormone is mainly responsible for ovulation in human females?

(A) FSH(B) LH(C) Progesterone(D) Oxytocin

Correct Answer: (B) LH

Human Reproduction

5. Fertilisation in humans normally occurs at the:

(A) Uterus(B) Cervix(C) Ampullary-isthmic junction of fallopian tube(D) Vagina

Correct Answer: (C) Ampullary-isthmic junction of fallopian tube

Human Reproduction

6. Which hormone maintains the endometrium during pregnancy?

(A) Progesterone(B) FSH(C) LH(D) Adrenaline

Correct Answer: (A) Progesterone

Reproductive Health

7. Which contraceptive method acts as a physical barrier preventing sperm from entering the female reproductive tract?

(A) Oral pills(B) Condom(C) Copper-T(D) Hormonal implant

Correct Answer: (B) Condom

Reproductive Health

8. Intrauterine transfer (IUT) involves transfer of an embryo into the:

(A) Ovary(B) Fallopian tube(C) Uterus(D) Cervix

Correct Answer: (C) Uterus

Reproductive Health

9. Amniocentesis can be used for:

(A) Determining blood pressure(B) Detecting certain genetic disorders(C) Increasing ovulation(D) Treating infertility directly

Correct Answer: (B) Detecting certain genetic disorders

Principles of Inheritance

10. A cross between Tt and tt gives the phenotypic ratio:

(A) 3:1(B) 1:1(C) 1:2:1(D) All tall

Correct Answer: (B) 1:1

Principles of Inheritance

11. The law of segregation states that:

(A) Alleles of a gene separate during gamete formation(B) Genes never change(C) Only dominant alleles are inherited(D) All genes assort independently

Correct Answer: (A) Alleles of a gene separate during gamete formation

Principles of Inheritance

12. A haemophilic male marries a normal homozygous female. Their sons are expected to be:

(A) All haemophilic(B) All normal with respect to haemophilia(C) 50% haemophilic(D) All carriers

Correct Answer: (B) All normal with respect to haemophilia

Molecular Basis of Inheritance

13. The enzyme that joins Okazaki fragments is:

(A) DNA polymerase(B) Helicase(C) DNA ligase(D) RNA polymerase

Correct Answer: (C) DNA ligase

Molecular Basis of Inheritance

14. The genetic material of most organisms is:

(A) RNA(B) DNA(C) Protein(D) Lipid

Correct Answer: (B) DNA

Molecular Basis of Inheritance

15. Synthesis of RNA from a DNA template is called:

(A) Translation(B) Replication(C) Transcription(D) Translocation

Correct Answer: (C) Transcription

Evolution

16. Hardy-Weinberg equilibrium describes a population in which:

(A) Allele frequencies change rapidly(B) Allele frequencies remain constant from generation to generation(C) Mutation is always absent(D) Natural selection is always intense

Correct Answer: (B) Allele frequencies remain constant from generation to generation

Evolution

17. The wings of a bird and butterfly are analogous because they:

(A) Have identical origin(B) Perform the same function but have different origins(C) Have identical embryonic structure(D) Are vestigial

Correct Answer: (B) Perform the same function but have different origins

Human Health and Disease

18. Antibody-secreting cells derived from activated B-lymphocytes are:

(A) Plasma cells(B) Helper T-cells(C) Memory T-cells(D) Macrophages

Correct Answer: (A) Plasma cells

Human Health and Disease

19. Malaria is caused by:

(A) Plasmodium(B) Salmonella(C) Entamoeba(D) Ascaris

Correct Answer: (A) Plasmodium

Human Health and Disease

20. HIV primarily attacks:

(A) Red blood cells(B) Helper T-lymphocytes(C) Platelets(D) B-lymphocytes only

Correct Answer: (B) Helper T-lymphocytes

Microbes in Human Welfare

21. The microorganism commonly used in bread and alcohol production is:

(A) Lactobacillus(B) Saccharomyces cerevisiae(C) Penicillium(D) Rhizobium

Correct Answer: (B) Saccharomyces cerevisiae

Biotechnology

22. Restriction enzymes are important in recombinant DNA technology because they:

(A) Join DNA fragments only(B) Cut DNA at specific recognition sites(C) Translate mRNA(D) Replicate proteins

Correct Answer: (B) Cut DNA at specific recognition sites

Biotechnology

23. PCR is used to:

(A) Amplify a specific DNA segment(B) Separate proteins(C) Produce antibodies directly(D) Destroy DNA

Correct Answer: (A) Amplify a specific DNA segment

Biotechnology

24. Bt cotton was developed mainly for resistance against:

(A) Bacterial diseases(B) Insect pests(C) Fungal diseases(D) Viral diseases

Correct Answer: (B) Insect pests

Ecology

25. The pyramid of energy in an ecosystem is always:

(A) Inverted(B) Upright(C) Spindle-shaped(D) Irregular

Correct Answer: (B) Upright