JIPMER Entrance Botany Flashcards

24 sample cards from the Botany deck

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

1. Where does the Krebs cycle occur and what are its products per turn (per acetyl-CoA)?

   In the mitochondrial matrix. Per acetyl-CoA: 3 NADH, 1 FADH2, 1 GTP (ATP), and 2 CO2 released.

2. Define respiratory quotient (RQ) and give the RQ for carbohydrates, fats and organic acids.

   RQ = volume of CO2 released / volume of O2 consumed. Carbohydrates: RQ = 1; fats: RQ < 1 (~0.7); organic acids: RQ > 1; proteins: ~0.9.

3. Name the five major plant growth hormones and one key function of each.

   Auxin (cell elongation, apical dominance); Gibberellin (stem elongation, seed germination, bolting); Cytokinin (cell division, delays senescence); Ethylene (fruit ripening, abscission); Abscisic acid/ABA (stomatal closure, dormancy, stress hormone).

4. What is photoperiodism and what are short-day, long-day, and day-neutral plants?

   Photoperiodism is the response of plants to the relative length of day/night for flowering. Short-day plants flower when day length is below a critical period; long-day plants flower when above it; day-neutral plants are unaffected by photoperiod.

5. What is vernalisation?

   The promotion of flowering by exposure to low temperature (cold treatment); required by certain plants (e.g., winter wheat) to flower.

6. Define the parts of a typical anther and the process of microsporogenesis.

   Anther is bilobed, tetrasporangiate; wall layers: epidermis, endothecium, middle layers, tapetum (nourishes pollen). Microsporogenesis = formation of haploid microspores from diploid microspore mother cells (pollen mother cells) by meiosis, forming microspore tetrads.

7. Describe the structure of a mature embryo sac (female gametophyte) in angiosperms.

   7-celled, 8-nucleate: 3 antipodal cells, 2 polar nuclei (in central cell), 1 egg cell and 2 synergids (egg apparatus). Develops from the functional megaspore (monosporic, Polygonum type).

8. Explain double fertilisation in angiosperms.

   One male gamete fuses with the egg cell (syngamy) to form the diploid zygote; the second male gamete fuses with the two polar nuclei (triple fusion) to form the triploid primary endosperm nucleus. Discovered by Nawaschin.

9. What are the contributions of Mendel's laws? State the Law of Segregation and Law of Independent Assortment.

   Law of Segregation: the two alleles of a gene separate during gamete formation, each gamete receiving only one. Law of Independent Assortment: alleles of different genes assort independently of one another during gamete formation.

10. What phenotypic and genotypic ratios result from a monohybrid and a dihybrid cross in F2?

    Monohybrid F2: phenotypic 3:1, genotypic 1:2:1. Dihybrid F2: phenotypic 9:3:3:1.

11. Define incomplete dominance and codominance with an example of each.

    Incomplete dominance: heterozygote shows an intermediate phenotype (e.g., pink Antirrhinum/Mirabilis from red × white). Codominance: both alleles expressed fully in heterozygote (e.g., AB blood group, IA and IB).

12. What is a test cross and what is its purpose?

    Crossing an individual of dominant phenotype (unknown genotype) with a homozygous recessive individual to determine whether the dominant individual is homozygous or heterozygous.

13. State Chargaff's rules and the structure of DNA per the Watson-Crick model.

    Chargaff's rules: A = T and G = C, so purines = pyrimidines. DNA is a right-handed antiparallel double helix; ~10 base pairs per turn; pitch 3.4 nm; distance between adjacent base pairs 0.34 nm; bases paired by H-bonds (A=T two, G≡C three).

14. What did the Meselson-Stahl experiment (1958) demonstrate?

    That DNA replication is semiconservative — each daughter DNA molecule has one parental (old) strand and one newly synthesised strand. Used 15N/14N density gradient centrifugation in E. coli.

15. Explain the lac operon and its components.

    An inducible operon in E. coli for lactose metabolism. Components: regulatory gene (i), promoter (p), operator (o), and structural genes z (β-galactosidase), y (permease), a (transacetylase). Lactose acts as inducer, inactivating the repressor so transcription proceeds.

16. What are the salient features of the genetic code?

    Triplet (codon of 3 nucleotides), degenerate (multiple codons per amino acid), unambiguous and specific, nearly universal, non-overlapping and comma-less. Start codon AUG (Met); stop codons UAA, UAG, UGA.

17. Define the ecological terms: population density, natality, mortality, and carrying capacity.

    Population density: number of individuals per unit area/volume. Natality: birth rate. Mortality: death rate. Carrying capacity (K): the maximum population size an environment can sustain.

18. Differentiate exponential growth and logistic growth equations.

    Exponential: dN/dt = rN (J-shaped curve, unlimited resources). Logistic: dN/dt = rN[(K−N)/K] (S-shaped/sigmoid curve, limited resources, K = carrying capacity).

19. What is the 10% law of energy transfer (Lindeman) and define ecological pyramids?

    10% law: only about 10% of energy is transferred from one trophic level to the next; the rest is lost as heat. Ecological pyramids represent number, biomass, or energy at each trophic level; the pyramid of energy is always upright.

20. What is ecological succession, and distinguish primary from secondary succession?

    Succession is the gradual, orderly change in species composition of a community over time leading to a climax community. Primary succession starts on bare/lifeless areas (no soil, e.g., bare rock, pioneers are lichens); secondary succession occurs where a community was destroyed but soil remains (faster).

21. What are the four major causes of biodiversity loss (the 'Evil Quartet')?

    Habitat loss and fragmentation, over-exploitation, alien species invasions, and co-extinctions.

22. Differentiate in-situ and ex-situ conservation with examples.

    In-situ: conservation in natural habitat (national parks, wildlife sanctuaries, biosphere reserves, sacred groves). Ex-situ: conservation outside natural habitat (zoos, botanical gardens, seed banks, cryopreservation, in vitro culture).

23. Name two genetically modified (Bt) crops used in agriculture and the source of the gene.

    Bt cotton and Bt corn/maize (also Bt brinjal). The cry genes (e.g., cryIAc, cryIIAb, cryIAb) producing Bt toxin are derived from the soil bacterium Bacillus thuringiensis, conferring resistance against insect pests.

24. How does RNA interference (RNAi) provide pest resistance, as used in nematode-resistant tobacco?

    RNAi silences specific mRNA by complementary double-stranded RNA. Tobacco plants are transformed to produce dsRNA matching nematode (Meloidogyne incognita) genes; the dsRNA silences the parasite's genes, so it cannot survive in the transgenic host.

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