CBSE Class 12 Biology Flashcards

24 sample cards from the Biology deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. In the lac operon, what role does the inducer (lactose/allolactose) play?

   The inducer binds to and inactivates the repressor protein, allowing RNA polymerase to transcribe the structural genes (z, y, a) for lactose metabolism.

2. What is the main goal of the Human Genome Project (HGP), and approximately how many genes were found?

   The HGP aimed to sequence all base pairs in the human genome (about 3 billion bp); it found approximately 20,000-25,000 genes.

3. What is the difference between transcription and translation?

   Transcription is synthesis of RNA from a DNA template (in the nucleus in eukaryotes). Translation is synthesis of a polypeptide (protein) from mRNA on ribosomes.

4. What did the Miller-Urey experiment demonstrate about the origin of life?

   It demonstrated chemical (abiogenic) origin of life: passing electric sparks through a mixture of CH4, NH3, H2, and water vapour produced amino acids, supporting Oparin-Haldane's theory.

5. Differentiate homologous organs from analogous organs, with one example each.

   Homologous organs have similar structure/origin but different functions (e.g., forelimbs of mammals) showing divergent evolution. Analogous organs have similar function but different structure/origin (e.g., wings of birds and insects) showing convergent evolution.

6. What is the Hardy-Weinberg principle, and what equation describes allele frequencies?

   It states that allele and genotype frequencies in a population remain constant across generations in the absence of evolutionary influences. Equation: p^2 + 2pq + q^2 = 1, where p + q = 1.

7. Name the five factors that can disturb Hardy-Weinberg equilibrium (cause evolution).

   Gene migration (gene flow), genetic drift, mutation, genetic recombination, and natural selection.

8. What does the example of industrial melanism in the peppered moth (Biston betularia) illustrate?

   It illustrates natural selection: dark moths increased in industrial (soot-covered) areas because they were better camouflaged from predators, demonstrating adaptation to environment.

9. Differentiate innate (non-specific) immunity from acquired (specific) immunity.

   Innate immunity is present from birth, non-specific (e.g., skin, phagocytes, inflammation). Acquired immunity is pathogen-specific, develops after exposure, and has memory (e.g., antibody-mediated and cell-mediated responses).

10. Differentiate active immunity from passive immunity.

    Active immunity: the body produces its own antibodies after exposure to antigen/vaccine (slow, long-lasting). Passive immunity: ready-made antibodies are given directly (e.g., mother's milk, antiserum) (fast, short-lived).

11. Name the causative organism and a key feature for malaria.

    Malaria is caused by Plasmodium (e.g., P. vivax, P. falciparum), transmitted by female Anopheles mosquito; it causes recurring chills and high fever due to release of haemozoin.

12. Which cells does HIV primarily attack, and what disease results?

    HIV attacks helper T-lymphocytes (CD4+ T cells), leading to AIDS (Acquired Immuno Deficiency Syndrome) by weakening the immune system.

13. What is the difference between a benign tumour and a malignant tumour?

    Benign tumours remain confined to their site and do not spread. Malignant tumours grow rapidly, invade surrounding tissues, and spread to distant sites via metastasis.

14. Define inbreeding and inbreeding depression in animal husbandry.

    Inbreeding is mating between closely related individuals of the same breed for 4-6 generations. Inbreeding depression is the reduced fertility and productivity resulting from continued inbreeding.

15. What is heterosis (hybrid vigour)?

    Heterosis is the superiority of crossbred/hybrid offspring over their parents in qualities like growth, yield, and disease resistance, achieved through outbreeding.

16. What is the difference between somatic hybridisation and micropropagation in plant breeding?

    Somatic hybridisation is fusion of protoplasts of two different plants to form a hybrid (somatic hybrid). Micropropagation is producing many plants through tissue culture, yielding genetically identical somaclones.

17. What is single cell protein (SCP)? Give an example organism.

    SCP is protein obtained from microbial biomass used as food/feed supplement, e.g., from Spirulina, mushrooms, or yeast (Saccharomyces).

18. What is biofortification?

    Biofortification is breeding crops with higher levels of vitamins, minerals, proteins, or healthier fats to improve public nutritional quality (e.g., vitamin-A enriched carrots/spinach).

19. Which microorganism is used to make curd from milk, and what does it produce?

    Lactic Acid Bacteria (LAB), e.g., Lactobacillus, convert milk to curd by producing lactic acid, which coagulates and partially digests milk proteins.

20. Which microorganism is used in baking bread and brewing, and what is it called?

    Saccharomyces cerevisiae (brewer's/baker's yeast); it ferments sugars producing CO2 (for bread rising) and ethanol (in brewing).

21. Name the organisms that produce the antibiotic penicillin and the drug cyclosporin A.

    Penicillin is produced by the fungus Penicillium notatum (discovered by Alexander Fleming). Cyclosporin A (an immunosuppressant) is produced by the fungus Trichoderma polysporum.

22. What are biogas, its main constituent, and the microbes involved?

    Biogas is a mixture of gases (mainly methane) produced by microbial activity (methanogens, e.g., Methanobacterium) on organic waste/sewage; it is used as fuel.

23. Name two microbes used as biofertilizers and the nutrient they provide.

    Rhizobium (symbiotic) and Azotobacter/Azospirillum (free-living) fix atmospheric nitrogen; mycorrhiza (Glomus) helps absorb phosphorus.

24. What is a biocontrol agent? Give one example used against insect pests.

    A biocontrol agent is a biological organism used to control pests/pathogens. Example: Bacillus thuringiensis (Bt) used against butterfly caterpillars; ladybird beetles against aphids.

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