CUET UG 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. What is single-cell protein (SCP) and biofortification?

   SCP is protein obtained from microbes (e.g., Spirulina, Methylophilus) grown in mass as an alternative source of protein for food/feed. Biofortification is breeding crops with higher levels of vitamins, minerals, or proteins (e.g., iron-rich rice, vitamin-A-enriched carrots, protein-rich wheat 'Atlas 66').

2. What are the three core techniques (tools) of recombinant DNA technology?

   (1) Restriction enzymes (molecular scissors) to cut DNA at specific sites; (2) cloning vectors (e.g., plasmids) to carry and replicate the foreign DNA; (3) DNA ligase to join DNA fragments. Also: a competent host cell to transform.

3. What is a restriction endonuclease, and what type of ends does it create?

   A restriction endonuclease cuts DNA at specific palindromic recognition sequences. Cutting between the same bases on both strands at slightly staggered positions produces single-stranded overhangs called 'sticky ends' (cohesive ends), e.g., EcoRI.

4. List the three steps of one PCR (Polymerase Chain Reaction) cycle.

   (1) Denaturation — DNA strands separate at high temperature (~94°C); (2) Annealing — primers bind to complementary sequences at lower temperature; (3) Extension — Taq DNA polymerase synthesizes new strands. The cycle is repeated to amplify DNA exponentially.

5. Why is Agrobacterium tumefaciens important in genetic engineering, and what is its Ti plasmid?

   Agrobacterium tumefaciens naturally transfers DNA into plant cells. Its Ti (tumour-inducing) plasmid is modified (disarmed) and used as a vector to deliver desired genes into plant cells, making it a key tool in producing transgenic plants.

6. What features must a good cloning vector possess?

   An origin of replication (ori) for autonomous multiplication, a selectable marker (e.g., antibiotic resistance gene) to identify transformants, unique recognition (restriction) sites for inserting foreign DNA, and (ideally) low molecular size with high copy number.

7. What is gel electrophoresis used for in genetic engineering, and which way do DNA fragments move?

   It separates DNA (or RNA) fragments by size. Since DNA is negatively charged (due to phosphate groups), fragments move toward the positive (anode) electrode through an agarose gel; smaller fragments move farther. Bands are visualized with ethidium bromide under UV light.

8. What is Bt cotton and how does the Bt toxin work?

   Bt cotton is a transgenic crop carrying cry genes from Bacillus thuringiensis. The bacterium produces inactive protoxin crystals (Cry proteins); when eaten by the insect, the alkaline gut pH solubilizes and activates the toxin, which binds the midgut epithelium, creating pores that swell and lyse cells, killing the pest (e.g., bollworm).

9. What is RNA interference (RNAi) and how was it used to make pest-resistant tobacco (Meloidogyne resistance)?

   RNAi is a cellular defense where double-stranded RNA silences a specific mRNA by complementary binding. Tobacco was made resistant to the nematode Meloidogyne incognita by introducing nematode-specific genes that produce dsRNA, silencing the parasite's mRNA so it cannot survive in the transgenic host.

10. What are gene therapy and ELISA, and give one application of each.

    Gene therapy is correcting a genetic defect by inserting a functional gene into a patient (first used for ADA deficiency / SCID). ELISA (Enzyme-Linked Immuno-Sorbent Assay) detects pathogens/antibodies by antigen-antibody interaction; used to diagnose diseases like HIV/AIDS.

11. Name two products made using genetically engineered organisms (transgenic/recombinant products) in medicine.

    Human insulin (Humulin, made in E. coli — produced as separate A and B chains then joined), human growth hormone, clotting factor VIII, hepatitis B vaccine, and recombinant interferon (any two).

12. How is recombinant human insulin produced, and how does it differ from earlier insulin?

    The genes for insulin's A and B polypeptide chains are inserted into E. coli plasmids; the bacteria produce the chains separately, which are then extracted and joined by disulfide bonds. Earlier insulin was extracted from pig/cattle pancreas and could cause allergy; recombinant insulin (Humulin) is identical to human insulin.

13. Define a population and name any three of its characteristic attributes.

    A population is a group of individuals of the same species living in a defined geographical area, sharing resources and able to interbreed. Attributes: birth rate (natality), death rate (mortality), sex ratio, age distribution (age pyramid), and population density.

14. Write the exponential and logistic population growth equations and define carrying capacity (K).

    Exponential growth: dN/dt = rN (J-shaped curve, unlimited resources). Logistic growth: dN/dt = rN[(K − N)/K] (S-shaped/sigmoid curve, limited resources). Carrying capacity (K) is the maximum population size the environment can sustainably support.

15. Match these population interactions to their effects (+/−): mutualism, competition, predation, parasitism, commensalism, amensalism.

    Mutualism (+ +): both benefit. Competition (− −): both harmed. Predation (+ −): predator benefits, prey harmed. Parasitism (+ −): parasite benefits, host harmed. Commensalism (+ 0): one benefits, other unaffected. Amensalism (− 0): one harmed, other unaffected.

16. What is an ecological pyramid, and which type is always upright?

    An ecological pyramid is a graphical representation of the relationship between trophic levels in terms of number, biomass, or energy. The pyramid of energy is always upright (energy decreases at each successive trophic level due to the 10% law).

17. State the 10 percent law of energy flow in an ecosystem (Lindeman).

    Only about 10% of the energy at one trophic level is transferred to and stored in the next trophic level; the remaining ~90% is lost mainly as heat (metabolic/respiration). This limits the number of trophic levels in a food chain.

18. Differentiate primary and secondary ecological succession.

    Primary succession starts on a bare, lifeless area with no pre-existing soil (e.g., bare rock, new volcanic land, cooled lava) and is very slow; the first colonizers (pioneer species) are usually lichens. Secondary succession occurs where a community was removed but soil remains (e.g., abandoned farmland, burnt forest) and is faster.

19. Distinguish gross primary productivity (GPP) from net primary productivity (NPP).

    GPP is the total rate of organic matter (energy) produced by photosynthesis. NPP is the GPP minus the energy used by producers in respiration (R): NPP = GPP − R. NPP is the biomass available to consumers (herbivores and decomposers).

20. What are the four levels (types) of biodiversity, and which level is measured by species richness?

    Genetic diversity, species diversity, and ecological/ecosystem diversity (sometimes also molecular/community). Species diversity is measured by species richness (the number of species per unit area).

21. Explain in-situ and ex-situ conservation with one example each.

    In-situ ('on site') conservation protects species in their natural habitat, e.g., national parks, wildlife sanctuaries, biosphere reserves, sacred groves. Ex-situ ('off site') conservation protects species outside their habitat, e.g., zoos, botanical gardens, seed banks, cryopreservation.

22. What is a biodiversity hotspot, and how many are recognized in India?

    A biodiversity hotspot is a region with very high species richness and a high degree of endemism that is under serious threat of habitat loss. India has 4 hotspots: the Himalayas, the Western Ghats, the Indo-Burma region, and Sundaland (Nicobar Islands).

23. List 'The Evil Quartet' — the four major causes of biodiversity loss.

    (1) Habitat loss and fragmentation (the most important cause), (2) over-exploitation, (3) invasion by alien (exotic) species, and (4) co-extinctions.

24. What do the IUCN Red List categories 'Endangered' and 'Extinct' indicate, and name one critically endangered/threatened Indian species.

    The IUCN Red List documents the conservation status of species. 'Endangered' = at very high risk of extinction in the wild; 'Extinct' = no living individuals remain. Example threatened Indian species: the great Indian bustard, the one-horned rhinoceros, or the Asiatic lion.

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