- Detection of internal organ cancers requires imaging techniques that can visualize tissues inside the body.

- Radiography uses X-rays to produce images of internal structures, helpful for tumors in dense tissues.

- MRI (Magnetic Resonance Imaging) produces detailed images of soft tissues, making it effective for detecting internal organ cancers.

- Computed Tomography (CT) scan combines X-ray images from multiple angles to create cross-sectional images of internal organs.

- Widal test is a serological test for typhoid fever, not for cancer detection.
Quick Tip: Remember: Imaging techniques like Radiography, MRI, and CT are used for detecting internal organ cancers. Blood tests like Widal test are disease-specific and not useful for cancer detection.

- Malaria is caused by protozoan parasites of the genus Plasmodium.

- \textit{Plasmodium falciparum causes the most severe form called malignant malaria, leading to complications like cerebral malaria and organ failure.

- Other species (\textit{P. vivax, P. malariae) cause milder forms.

- Correct identification is crucial for appropriate treatment.
Quick Tip: Associate \textit{P. falciparum with severe/malignant malaria, while P. vivax and P. malariae cause milder disease.

- Cyclosporin-A is an immunosuppressive drug used to prevent organ transplant rejection.

- It inhibits T-lymphocyte activity to prevent immune-mediated damage to transplanted organs.

- Cyclosporin-A is a cyclic peptide produced by the fungus Trichoderma polysporum.

- Other options like statins are produced by different fungi (\textit{Monascus purpureus) and are used for cholesterol control, not transplant medicine.
Quick Tip: Connect Cyclosporin-A with organ transplant and \textit{Trichoderma polysporum. Remember: immunosuppressive drugs prevent graft rejection.

- Biocontrol uses living organisms to control pests and pathogens in crops instead of chemical pesticides.

- Examples include \textit{Trichoderma, \textit{Bacillus thuringiensis, and predatory insects.

- \textit{Trichoderma species act against fungal pathogens through competition, antibiosis, and mycoparasitism, making them effective biocontrol agents.
Quick Tip: Remember: Biocontrol = use of living organisms. Trichoderma is a fungal biocontrol agent effective against plant pathogens.

- a) Streptococcus is matched with ii) Colt buster, as it is known to cause diseases like strep throat and is associated with colt-related infections.
- b) Penicillium is matched with iii) Source of antibiotic, as it produces penicillin, a well-known antibiotic.
- c) Methanogens are matched with iv) Biogas production, as they produce methane gas used in biogas.
- d) Anabaena is matched with i) Free living nitrogen fixing bacteria, as it is a cyanobacterium that fixes nitrogen in the soil.

Thus, the correct matching is a-ii, b-iii, c-iv, d-i.
Quick Tip: Match based on biological roles: Antibiotics from fungi, nitrogen fixation by cyanobacteria, biogas from methanogens.

- a) Bioreactors are matched with ii) Vessels which convert raw material into specific product, as they are used to facilitate biological reactions.
- b) Downstream processing is matched with iv) Involves separation and purification, as it includes the steps to purify products after biosynthesis.
- c) Recombinant protein is matched with i) Insulin produced by rDNA technology, as recombinant DNA technology is used to produce insulin.
- d) PCR is matched with iii) Detect mutated genes in suspected cancer patient, as it is a technique used to amplify DNA for genetic analysis.

Thus, the correct matching is a-ii, b-iv, c-i, d-iii.
Quick Tip: Understand biotechnology processes: Bioreactors for conversion, downstream for purification, rDNA for proteins, PCR for gene detection.

- Plasmids like pBR322 have an origin of replication (Ori) that allows autonomous replication in host cells.

- "rop" gene regulates plasmid copy number, not replication directly.

- Cloning site is used for insertion of foreign DNA.

- Selectable markers (e.g., antibiotic resistance) allow identification of transformed cells.
Quick Tip: Ori site = origin of replication, essential for plasmid duplication. Remember distinction between regulatory genes, cloning site, and selectable marker.

- Fungal cell walls contain chitin → use Chitinase to break them.

- Bacterial cell walls contain peptidoglycan → Lysozyme hydrolyzes the β-1,4-glycosidic linkages in peptidoglycan.

- Plant cell walls contain cellulose → Cellulase is required to degrade cellulose for DNA extraction.
Quick Tip: Match the enzyme to the major structural polymer of the cell wall: Chitin (fungi), Peptidoglycan (bacteria), Cellulose (plants).

- Insulin is initially synthesized as preproinsulin → proinsulin → mature insulin.

- Proinsulin has A, B, and C peptides.

- During maturation, C-peptide is cleaved off, leaving A and B chains linked by disulfide bonds.

- Therefore, mature insulin contains only A and B peptides; C-peptide is not present.
Quick Tip: Remember: C-peptide is removed to activate insulin. Its measurement in blood is used to assess endogenous insulin production.

- Apical and axillary meristems are regions of actively dividing cells at the tips and nodes of plants.

- These meristems are often free from systemic viruses because they grow faster than virus spread.

- Mature stem and mesophyll cells may contain viruses; thus, they are not ideal for virus-free cultures.
Quick Tip: For virus-free plant tissue culture, always use apical or axillary meristem. Fast-dividing meristematic cells exclude viruses.

- Bacillus thuringiensis (Bt) produces Cry proteins toxic to specific insects.

- Targets include Lepidopteran larvae like cotton bollworm, tobacco budworm, armyworm.

- Tapeworm is a helminth (parasitic worm) not susceptible to Bt toxins.
Quick Tip: Bt toxins are insect-specific; they do not affect mammals or helminths. Know the Lepidopteran pests targeted.

- Population density increases if the number of individuals entering or born exceeds those leaving or dying.

- Natality (birth rate) adds individuals; Immigration brings individuals from other populations.

- Mortality (death rate) and Emigration reduce population density.
Quick Tip: For population growth: \textbf{Increase factors = Natality + Immigration, Decrease factors = Mortality + Emigration}.

- Death rate = Number of deaths / Total population

- Here, Number of deaths = 8, Population = 80
\[ Death rate = \frac{8}{80} = 0.1 individual/time interval \]
- This indicates that 10% of the population died during that interval.
Quick Tip: Death rate is calculated as deaths divided by total population. Always convert numbers to the same unit (individuals/time interval) for clarity.

- Decomposition is the breakdown of organic matter by detritivores and microbes.

- Step 1: Fragmentation – larger debris is broken into smaller pieces by detritivores.

- Step 2: Leaching – soluble substances are removed by water.

- Step 3: Catabolism – microbial enzymatic breakdown of organic molecules.

- Step 4: Humification – formation of humus from partially decomposed matter.

- Step 5: Mineralisation – conversion of organic nutrients into inorganic forms usable by plants.
Quick Tip: Remember the decomposition sequence: Fragmentation → Leaching → Catabolism → Humification → Mineralisation. Focus on the order from physical breakdown to chemical conversion.

- Ecological pyramids represent energy, biomass, or numbers in trophic levels.

- Limitations:

- a) Cannot show species in multiple trophic levels (e.g., omnivores).

- b) Assumes linear food chain; real ecosystems are complex food webs.

- d) Cannot accommodate complex food webs.

- Saprophytes are decomposers and not represented in trophic pyramids.
Quick Tip: Remember: Pyramids simplify ecosystems; they cannot depict omnivores, saprophytes, or food webs.

- The Sixth Extinction refers to the rapid ongoing loss of species caused by human activities.

- Current extinction rates are estimated 1000–10000 times higher than background rates observed in previous mass extinctions.

- Causes include habitat destruction, overexploitation, pollution, invasive species, and climate change.
Quick Tip: Associate 'Sixth Extinction' with human-driven species loss, much faster than natural historical extinctions.

- Latitudinal gradient of biodiversity: species diversity is highest at the equator and decreases toward the poles.

- Factors: stable climate, higher primary productivity, and more complex habitats in tropics.

- Polar regions have extreme climates and fewer resources, limiting species diversity.
Quick Tip: Remember: Tropical regions (Equator) = high diversity; Polar regions = low diversity. This is a fundamental pattern in ecology.

A pedigree chart helps determine the inheritance pattern based on distribution of affected individuals across generations and sexes.

- Sex-linked recessive traits appear more in males because they have only one X chromosome.
- Affected males pass the trait to all daughters (carriers), not sons.
- The trait can skip generations.

Assuming I-1 is affected male, II-2 carrier daughter, III-1 affected male, this matches sex-linked recessive inheritance seen in hemophilia or color blindness.

- Autosomal dominant: affects both sexes equally, does not skip generations.
- Autosomal recessive: requires both parents to be carriers, affects both sexes.
- Sex-linked dominant: more females affected, does not skip generations.

Thus, correct identification is sex-linked recessive. Quick Tip: Look for male predominance and carrier females in pedigrees to identify sex-linked recessive traits.

- Conjoint collateral vascular bundles = xylem and phloem together.

- Open vascular bundles have a cambium between xylem and phloem → capable of secondary growth.

- Monocot stems show open, conjoint collateral bundles arranged scattered in ground tissue.

- Roots usually have radial or closed bundles; dicot stems have closed bundles arranged in a ring.
Quick Tip: Key identifiers: Conjoint + open → Monocot stem; Conjoint + closed → Dicot stem; Radial → Root.

- Telophase is the stage where separated chromatids reach opposite poles.

- Nuclear membrane re-forms around each set; chromosomes decondense into chromatin.

- Metaphase → chromosomes aligned at equatorial plate; Anaphase → chromatids separate; Prophase → chromosomes condense.
Quick Tip: Identify mitotic stages: Chromosome location and spindle attachment are key. Chromosomes at poles = Telophase.

- Biological names are always Latin or Latinised; italics indicate scientific naming convention, not origin.

- First word = genus (capitalized), second = specific epithet (lowercase).

- When handwritten, underline both words separately.
Quick Tip: Remember: Italics indicate scientific naming format, not non-Latin origin. Genus capitalized, species lowercase.

a) Coccus: Refers to spherical-shaped bacteria, so it matches with iii.


b) Bacillus: Refers to rod-shaped bacteria, so it matches with i.


c) Vibrio: Refers to comma-shaped bacteria, so it matches with iv.


d) Spirillum: Refers to spiral-shaped bacteria, so it matches with ii.

Thus, the correct matching is a-iii, b-i, c-iv, d-ii. Quick Tip: Match bacterial shapes with their morphological characteristics for accurate pairing.

- Gemmae are asexual buds, not sexual. They develop in gemma cups for vegetative propagation.

- Protonema is the first filamentous stage of a moss, which develops directly from a haploid spore.
Quick Tip: Gemmae = asexual, not sexual. Protonema originates from spore in bryophytes.

- Balanoglossus is a hemichordate with tripartite body: proboscis, collar, trunk.

- Pterophyllum = freshwater fish; Trygon = stingray; Ophiura = echinoderm (brittle star).
Quick Tip: Body divisions help in identifying hemichordates. Proboscis + collar + trunk = Balanoglossus.

Aestivation is the arrangement of petals or sepals in a flower bud.

- Vexillary: one posterior petal overlaps two lateral petals (e.g., pea).
- Imbricate: irregular overlapping (e.g., Cassia).
- Twisted: one margin overlaps adjacent petal (e.g., China rose).
- Valvate: edges meet, no overlapping (e.g., mustard).

Assigning labels logically:

- 'a' → Vexillary
- 'b' → Imbricate
- 'c' → Twisted
- 'd' → Valvate

Thus, option (1) is correct. Quick Tip: Recall aestivation types with examples: Vexillary (pea), Imbricate (Cassia), Twisted (China rose), Valvate (mustard).

- a (Radial, tetrarch, cambial ring at later stages) matches ii (T.S of dicot root): Dicot roots have radial bundles and typically a diarch to tetrarch number of xylem groups. Though typically cambial rings form during secondary growth, the core root characteristics are radial and tetrarch.

- b (Conjoint, open and endarch) matches iv (T.S of dicot stem): Dicot stems have conjoint (xylem and phloem together), open (presence of cambium), and endarch (protoxylem towards the pith) vascular bundles.

- c (Radial, Polyarch, large pith without cambial ring) matches iii (T.S of monocot root): Monocot roots have radial bundles, polyarch (many xylem groups), a large pith, and lack a cambial ring as they do not undergo secondary growth.

- d (Conjoint, closed with sclerenchymatous bundle sheath) matches i (T.S of monocot stem): Monocot stems have conjoint, closed (absence of cambium) bundles, often surrounded by a prominent sclerenchymatous bundle sheath.

- The correct matching combination is \(\mathbf{a - ii, b - iv, c - iii, d - i}\).
Quick Tip: Remember the key rules: \textbf{Roots} are \textbf{Radial}, \textbf{Stems} are \textbf{Conjoint}. \textbf{Dicot stems} are \textbf{Open} (cambium), \textbf{Monocot stems} are \textbf{Closed} (no cambium).

- Male frogs have Bidder’s canals in testes for sperm transport.

- Copulatory pads are present in males to hold female during amplexus, not females.

- Vocal sacs in male frogs help amplify mating calls.

- Cloaca is present in both male and female frogs for excretion and reproduction.
Quick Tip: Remember: Male frogs → Bidder’s canals + vocal sacs + copulatory pads; Cloaca in both sexes.

- Prokaryotic cells store reserve materials as inclusion bodies in the cytoplasm.

- Examples: glycogen granules, polyhydroxybutyrate granules, sulfur granules.

- Exclusion bodies refer to pathological aggregates; fat bodies are storage in some eukaryotes.
Quick Tip: In prokaryotes: Inclusion bodies = nutrient storage in cytoplasm.

- Mycoplasma are prokaryotes that naturally lack a cell wall.

- Other prokaryotes like Cyanobacteria, Bacteria, and Blue-Green Algae have peptidoglycan-based cell walls.

- Lack of cell wall allows flexibility but makes them sensitive to osmotic stress.
Quick Tip: Cell wall absent = Mycoplasma; Remember it’s the only naturally wall-less prokaryote.

In enzyme kinetics, activation energy is the energy barrier for a reaction.

- Without enzyme: higher activation energy (M).
- With enzyme: lower activation energy (N), as enzyme stabilizes the transition state.

Graph shows:

- Higher peak: uncatalyzed reaction
- Lower peak: catalyzed reaction

Options about temperature or substrate are irrelevant to activation energy. Correct identification is M → without enzyme, N → with enzyme. Quick Tip: Enzymes lower activation energy; identify peaks in energy profiles for catalyzed vs. uncatalyzed reactions.

a) Leptotene: Chromosomes appear as thin threads, so it matches with iv.


b) Zygotene: Homologous chromosomes pair up and become shorter and thicker, so it matches with i.


c) Pachytene: Crossing over occurs between homologous chromosomes, so it matches with ii.


d) Diplotene: Chromosomes start to separate, and crossing over is visible, so it matches with iii.


e) Diakinesis: Terminalization of chiasmata occurs, so it matches with v.


Thus, the correct matching is a-iv, b-i, c-ii, d-iii, e-v. Quick Tip: Understand the sequence and key events of prophase I stages for accurate matching.

- Calvin cycle (C3 pathway) uses RuBP Carboxylase (Rubisco) for carboxylation of RuBP with CO\(_2\).

- Hatch-Slack pathway (C4 pathway) uses PEP Carboxylase to fix CO\(_2\) into oxaloacetate.

- Statement I is reversed; Statement II is true.
Quick Tip: C3: RuBP Carboxylase; C4: PEP Carboxylase. Do not confuse Calvin and Hatch-Slack pathways.

- In the TCA (Krebs) cycle, acetyl-CoA (2C) condenses with oxaloacetic acid (4C) to form citric acid (6C).

- This is catalyzed by citrate synthase.

- α-Ketoglutarate and succinate are intermediate compounds formed later.
Quick Tip: TCA start: Acetyl-CoA + Oxaloacetate → Citrate. Key for remembering Krebs cycle entry step.

- a (Auxin) is an Indole compound (ii), as the primary natural auxin, Indole-3-acetic acid (IAA), is an indole derivative.

- b (Gibberellin) is a Terpene (iv). Gibberellins (GAs) are synthesized from mevalonic acid pathway intermediates, which classify them as terpenes.

- c (Cytokinin) is an Adenine derivative (i), with the main natural form (Zeatin) being a modified adenine.

- d (Abscisic acid - ABA) is a Carotenoid derivative (iii), specifically synthesized from cleavage of carotenoids (xanthophylls) in plants.

- The correct match is: \(\mathbf{a-iii, b-iv, c-i, d-ii}\).
Quick Tip: Remember the chemical classes: Auxin \(\rightarrow\) Indole; Cytokinin \(\rightarrow\) Adenine; Gibberellin \(\rightarrow\) Terpene; Abscisic Acid \(\rightarrow\) Carotenoid.

- Medulla oblongata controls involuntary respiration via respiratory centers.

- Pneumotaxic center in pons regulates rate and depth of breathing.

- Chemoreceptive areas detect CO\(_2\), O\(_2\) and pH changes to modify respiration.

- Corpus callosum is for brain hemispheric communication; not respiratory control.
Quick Tip: Respiration centers: Medulla + Pons → control breathing rate and depth. Remember chemoreceptors for feedback.

- Blood vessels have three layers:

1. Tunica intima: Innermost endothelial layer, providing smooth lining for blood flow.

2. Tunica media: Middle layer made of smooth muscle and elastic fibers, regulates vessel diameter and blood pressure.

3. Tunica externa (adventitia): Outer connective tissue layer, provides mechanical support and prevents overexpansion.

- In arteries, tunica media is thick due to high pressure and elastic recoil.

- In veins, tunica media is thin as veins operate under lower pressure and rely on valves and surrounding skeletal muscles for blood return.

- Tunica externa is relatively thicker in veins to provide structural support.
Quick Tip: Artery: Thick tunica media; Vein: Thin tunica media, thick tunica externa. Always link thickness to pressure handled by the vessel.

- The counter-current mechanism is crucial for concentrating urine and maintaining osmotic gradient in kidney medulla.

- Components: Henle's loop (descending and ascending limbs) and Vasa Recta (peritubular capillaries).

- Mechanism:

1. Descending limb is permeable to water but not solutes → water moves out, concentrating filtrate.

2. Ascending limb is impermeable to water but actively pumps out Na\(^+\) and Cl\(^-\) → dilutes filtrate.

3. Vasa recta maintains osmotic gradient by absorbing water and solutes in opposite direction (counter-current exchange).

- Collecting duct also participates but counter-current system is defined by Henle’s loop + Vasa Recta.
Quick Tip: Counter-current mechanism = Henle + Vasa Recta. Remember: descending = water out, ascending = salts out, maintains medullary osmotic gradient.

- Skeletal muscle contraction follows the sliding filament theory:

1. Thin filaments (actin) slide over thick filaments (myosin).

2. A-band (length of myosin) remains constant as thick filaments do not shorten.

3. I-band (region with only actin) reduces as filaments slide over each other.

4. Z-lines move closer, shortening the sarcomere and thus the whole muscle.

- So, I-bands shorten, A-bands retain length during contraction.
Quick Tip: Sliding filament theory: A-band constant, I-band shortens. Z-line movement indicates contraction.

- Steps of neurotransmission at chemical synapse:

1. Arrival of action potential at axon terminal.

2. Depolarization opens voltage-gated Ca\(^{{2+}}\) channels → synaptic vesicles release neurotransmitter.

3. Neurotransmitter diffuses across the synaptic cleft.

4. Binds to receptors on post-synaptic membrane, generating postsynaptic potential.

5. Signal propagates in post-synaptic neuron.

- Sequence reflects the correct flow of information in chemical synapses.
Quick Tip: Synapse steps: AP arrives → vesicles release → cleft diffusion → postsynaptic binding → neuron activation.

- Cortisol is a glucocorticoid hormone from adrenal cortex; its main functions:

1. Maintains cardiovascular function by sensitizing vessels to catecholamines → i is true.

2. Anti-inflammatory action by inhibiting cytokines and prostaglandins → ii is true.

3. Does not directly maintain electrolyte balance, osmosis, or BP → iii is false; aldosterone is responsible for these.

4. Suppresses immune response (iv) → actually true for preventing excessive immunity.

5. Does not stimulate RBC production (v) → this is function of erythropoietin.
Quick Tip: Cortisol = stress hormone, anti-inflammatory, regulates metabolism. Electrolytes & BP → aldosterone, not cortisol.

- Xenogamy = cross-pollination between different plants → genetic variation.

- Autogamy = self-pollination within the same flower.

- Geitonogamy = transfer of pollen between flowers of the same plant.

- Dichogamy = temporal separation of male and female maturation in same flower.
Quick Tip: Xenogamy = cross-plant fertilization; remember: auto = self, geito = same plant, dichogamy = timing difference.

- In angiosperms, double fertilization occurs:

1. One sperm fuses with egg → forms zygote (syngamy).

2. Other sperm fuses with two polar nuclei in central cell → forms triploid primary endosperm (triple fusion).

- Apomixis = asexual seed formation without fertilization.

- So, fusion with central cell specifically = triple fusion.
Quick Tip: Double fertilization: sperm + egg = zygote; sperm + 2 polar nuclei = triploid endosperm (triple fusion). Key for angiosperms.

Pollen grain contains:

- Generative cell: divides to form two male gametes during pollen tube growth.
- Vegetative cell: larger cell forming pollen tube with food reserves.

In diagram:

- 'A' → generative cell → male gametes
- 'B' → vegetative cell → pollen tube

Option (3) correctly assigns roles. Quick Tip: Remember: Generative cell → male gametes, Vegetative cell → pollen tube in pollen grain structure.

- a (hCG and hPL) are produced primarily by the Placenta (ii).

- b (Progesterone) is initially produced by the Corpus luteum (iii) and later in pregnancy also by the placenta.

- c (Androgens) are produced by the Leydig cells (iv) in the testes.

- d (Relaxin) is produced by the Ovary (i) (specifically the corpus luteum) and the placenta during pregnancy.

- The correct matching combination is \(\mathbf{a-ii, b-iii, c-iv, d-i}\).
Quick Tip: Hormones like hCG and hPL are unique to pregnancy and are placental hormones. Progesterone and Relaxin have multiple sources during the reproductive cycle.

- Seminiferous tubules: site of spermatogenesis in testes.

- Rete testis: network connecting seminiferous tubules to vasa efferentia.

- Vasa efferentia: transport sperm from rete testis to epididymis.

- Epididymis: sperm maturation and storage.

- Vas deferens: muscular tube carrying sperm from epididymis to ejaculatory duct.

- Ejaculatory duct: connects vas deferens to urethra for ejaculation.

- Sequence reflects proper anatomical flow from sperm production to release.
Quick Tip: Sperm transport sequence: Testes → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra.

- First month: Formation of heart begins (organogenesis starts).

- Second month: Limbs, fingers, eyes develop; foetal movement is minimal and not perceptible externally (movements usually detectable ~4th–5th month).

- Third month: Major organ systems completed.

- Sixth month: Eyelids separate, eyelashes and eyebrows develop.

- Therefore, statement b is mismatched.
Quick Tip: Foetal development: Heart → month 1; Limbs, face → month 2; Organ systems → month 3; Eye lashes & external features → month 6.

- Natural methods: No artificial device or chemical, e.g.,

- Lactational amenorrhea (temporary infertility during breastfeeding).

- Periodic abstinence (avoiding intercourse during fertile period).

- Coitus interruptus (withdrawal method).

- Implants: artificial hormonal device → artificial method, not natural.
Quick Tip: Natural contraception = no devices or chemicals; Implants and IUDs are artificial methods.

- ZIFT (Zygote Intrafallopian Transfer): fertilized zygote (1-cell) cultured in vitro until 8-cell stage.

- Embryo then transferred into fallopian tube for natural implantation in uterus.

- Advantages: allows natural transport to uterus, mimics in vivo fertilization timing.

- Later stages (16, 32 blastomeres) are transferred in IVF directly into uterus.
Quick Tip: ZIFT = 1-cell → 8-cell zygote into fallopian tube; IVF embryo transfer = later stage into uterus.

- MTP (Medical Termination of Pregnancy) is performed to terminate unwanted pregnancy safely.

- Legal requirements: must be done by certified doctors in authorized clinics with proper medical justification.

- Statement I correctly explains purpose; Statement II correctly explains legal framework.
Quick Tip: MTP = safe, legal abortion. Key: both purpose and legal execution must be considered.

- Number of gametes = \( 2^n \), where \( n \) = number of heterozygous loci.

- Given genotype: AaBbCc → 3 heterozygous loci (A, B, C).

- Total gametes = \( 2^3 = 8 \).

- Possible gametes: ABC, ABc, AbC, Abc, aBC, aBc, abC, abc.
Quick Tip: Gametes = combination of alleles from heterozygous loci only. Formula: 2\(^n\), n = number of heterozygotes.

- Pleiotropy: single gene influences multiple, apparently unrelated traits.

- Example: Marfan syndrome → mutation in fibrillin gene affects skeletal system, eyes, cardiovascular system.

- Co-dominance → both alleles expressed equally.

- Polygenic inheritance → multiple genes affect single trait.

- Incomplete dominance → heterozygote shows intermediate phenotype.
Quick Tip: Pleiotropy = one gene, multiple effects. Polygenic = many genes, one effect. Co-dominance = both alleles expressed. Incomplete = intermediate.

- Colour blindness: X-linked recessive (X\(^c\)).

- Father: X\(^c\)Y; Mother: X\(^C\)X\(^c\) (carrier).

- Punnett square: \[ \begin{array}{c|cc} & X^C & X^c
\hline X^c & X^C X^c & X^c X^c
Y & X^C Y & X^c Y \end{array} \]
- Progeny: 2 out of 4 males will be colourblind → 50%. Females: 1 carrier, 1 affected → only males counted usually.
Quick Tip: X-linked recessive inheritance: Males XY, Females XX. Carrier female + affected male → 50% sons affected, 50% daughters carriers.

- Pair (c) is correct: Down's Syndrome is characterized by broad palms and intellectual/physical developmental delays. Turner's Syndrome is characterized by sterile females with underdeveloped (rudimentary) ovaries.

- Pair (a) is incorrect: Gynaecomastia is a feature of Klinefelter's Syndrome (\(\mathbf{47, XXY}\)), not Turner's Syndrome (\(\mathbf{45, X}\)).

- Pair (b) is incorrect: Overall masculine development does not describe Turner's Syndrome (which results in sterile females).

- Pair (d) is incorrect: The Down's Syndrome feature listed (additional copy of an X-chromosome) describes Klinefelter's Syndrome (\(\mathbf{47, XXY}\)), not Down's (which is Trisomy 21).
Quick Tip: Associate \textbf{Down's Syndrome} with \textbf{Trisomy 21} (autosomal), and \(\mathbf{47}\) total chromosomes. Associate \textbf{Turner's Syndrome} with \(\mathbf{45, X}\) (monosomy of sex chromosome), resulting in sterile female features.

- RNA polymerase II transcribes heterogeneous nuclear RNA (hnRNA), which is processed into mRNA in eukaryotes.

- RNA polymerase I → rRNA, RNA polymerase III → tRNA and 5S rRNA.

- hnRNA contains introns and exons → splicing yields mature mRNA.
Quick Tip: Eukaryotic transcription: Pol I → rRNA, Pol II → mRNA/hnRNA, Pol III → tRNA \& 5S rRNA.

- Lac permease: membrane protein facilitating uptake of lactose into bacterial cell.

- β-galactosidase: hydrolyses lactose → glucose + galactose.

- Transacetylase: detoxifies non-metabolizable lactose analogues.

- Amylase: hydrolyzes starch, irrelevant for lactose.
Quick Tip: Lactose uptake: Permease brings lactose in, β-galactosidase breaks it down. Permease increases membrane permeability to lactose.

- Prokaryotic genome characteristics:

- Usually polycistronic operons exist (one mRNA codes for multiple proteins), so option 1 is incorrect.

- Introns are absent in prokaryotic structural genes → option 2 correct.

- Transcription and translation are coupled in cytoplasm since no nucleus → option 3 correct.

- No splicing occurs in prokaryotes → option 4 incorrect.

- Single RNA polymerase synthesizes all RNA types → option 5 correct.
Quick Tip: Prokaryotic genome: Polycistronic operons, no introns, transcription \& translation coupled, single RNA polymerase, no splicing.

- Genetic drift: Random fluctuations in allele frequencies due to chance, especially in small populations.

- Example: A few individuals reproduce by chance → some alleles may be lost.

- Distinction:

- Founder effect: a type of genetic drift in new populations.

- Genetic recombination: exchange of alleles during meiosis.

- Gene migration: movement of alleles between populations.
Quick Tip: Genetic drift = random allele frequency change; more pronounced in small populations; includes founder effect.

- Adaptive radiation: diversification of a single ancestral species into multiple species adapted to different ecological niches.

- Darwin’s finches on Galapagos Islands: different beak shapes evolved according to food sources.

- Not chemical evolution (origin of life), not genetic equilibrium (population stability), not migration.
Quick Tip: Adaptive radiation = one species → multiple species in different niches; classic example: Darwin's finches.

- 1) True: Darwin's voyage on HMS Beagle (1831–1836).

- 2) True: gradual evolution through natural selection.

- 3) False: fitness = reproductive success, not physical fitness.

- 4) True: fossils = preserved hard parts (bones, shells) of organisms.

- 5) False: Hugo De Vries worked on mutation theory in the Netherlands, not Malay Archipelago.
Quick Tip: Darwin facts: HMS Beagle voyage, gradual evolution, fitness = reproductive success; fossils preserve hard parts; De Vries = mutation theory, Netherlands.

- HIV targets CD4+ cells: mainly helper T-lymphocytes.

- Virus binds to CD4 receptor + co-receptor → enters cell → reverse transcription → viral replication → new virions released.

- Killer T-cells (cytotoxic) destroy infected cells, not main replication site.

- Suppressor and memory T-cells less affected.
Quick Tip: HIV = retrovirus; primary target = CD4+ helper T-cells; replication occurs inside helper T-lymphocytes, reducing immune defense.