• n (haploid): Found in antipodal cells.
• 2n (diploid): Found in the zygote formed by fertilization.
• 3n (triploid): Found in the endosperm formed by double fertilization.

This distribution of ploidy levels is a characteristic feature of angiosperm reproduction.

• Turner’s syndrome is caused by the absence of one X chromosome, resulting in a 45, XO chromosomal pattern.
• This is a type of aneuploidy, which refers to the presence of an abnormal number of chromosomes.

Turner’s syndrome affects females and is characterized by short stature, infertility, and other physical abnormalities.

• P – Transcription: The process of synthesizing mRNA from DNA.
• Q – mRNA: Serves as a template for protein synthesis.
• R – Translation: The process where the mRNA sequence is decoded to synthesize a protein.

The Central Dogma describes the flow of genetic information from DNA to RNA to Protein.

• A – Connective: Tissue joining the two lobes of the anther.
• B – Endothecium: The outer layer of the pollen sac that provides mechanical support.
• C – Pollen grain: The male gametophyte formed within the pollen sac.

The anther is a bilobed structure that contains microsporangia, which develop into pollen sacs housing pollen grains.

• Ovum (B): The unfertilized egg.
• Morula (D): A solid ball of cells formed after a series of mitotic divisions.
• Blastocyst (G): A hollow structure in early embryonic development that implants into the uterine wall.

The blastocyst stage is critical for implantation into the uterine lining, marking the beginning of pregnancy.

• A – The pill: Inhibits ovulation (III).
• B – Condom: Prevents sperm from reaching the cervix (I).
• C – Vasectomy: Semen contains no sperm after the vas deferens is cut or tied (IV).
• D – Copper-T: Prevents implantation of the fertilized egg (II).

• The disorder is seen in both males and females, indicating autosomal inheritance.
• It skips generations, suggesting recessive inheritance.
• Affected offspring have parents who are carriers of the recessive allele.

Autosomal recessive disorders often require both parents to contribute the recessive allele for the disorder to manifest in offspring.

• ELISA (Enzyme-Linked Immunosorbent Assay) detects specific antigens or antibodies using the principle of antigen-antibody interaction.
• The binding is detected through an enzyme-linked reaction, often resulting in a color change.

ELISA is extensively used in medical diagnostics, such as detecting infections like HIV and hepatitis.

• Homologous organs have a similar structure but may perform different functions, e.g., human arm and bat wing.
• These similarities suggest a common ancestor and illustrate divergent evolution.

Divergent evolution demonstrates how species adapt differently to various environments while sharing a common ancestry.

• Restriction enzymes, also known as molecular scissors, cut DNA at specific recognition sequences.
• They are widely used in genetic engineering and molecular biology for cloning and gene editing.

Restriction enzymes revolutionized molecular biology, enabling precise DNA manipulation for research and therapeutic purposes.

• The Y chromosome is the smallest human chromosome and contains the least number of genes.
• It carries genes essential for male sex determination and spermatogenesis.

• Cyclosporin-A: Produced by Monascus purpureus, used as an immunosuppressant.
• Statins: Derived from Trichoderma polysporum, these lower blood cholesterol.
• Streptokinase: Obtained from Streptococcus, used to remove blood clots.
• Penicillin: Produced by Penicillium notatum, an antibiotic effective against bacterial infections.

• Plasmids are circular DNA molecules capable of autonomous replication.
• They are commonly found in prokaryotic cells like bacteria, not in eukaryotic cells.

• Patents are legal rights granted to inventors for exclusive use of their inventions.
• Preventing unauthorized use is the primary reason for granting patents, ensuring inventors can commercialize their inventions without competition for a limited time.

• Fig and wasp share an obligate mutualistic relationship where each depends on the other for survival and reproduction.
• Wasps pollinate the fig while laying eggs, ensuring mutual benefit.

• Inverted biomass pyramids occur in aquatic ecosystems where the biomass of primary consumers exceeds that of producers.
• More energy is required by organisms occupying higher trophic levels, but this does not explain why inverted biomass pyramids occur in aquatic ecosystems.

• Artificial Insemination: A technique in Assisted Reproductive Technology (ART) where semen is artificially introduced into the female reproductive tract.
• Conditions for Medical Advice:
  • When the male partner has a low sperm count or poor sperm motility.
  • In cases of physical or anatomical issues in natural intercourse.

• Repeated Infusions:
  • ADA (Adenosine Deaminase) deficiency leads to severe immune system dysfunction.
  • Repeated infusions of genetically engineered lymphocytes temporarily restore immune function by providing the necessary enzyme.
• Permanent Remedy:
  • Gene therapy to introduce a functional ADA gene into the patient’s bone marrow cells.
  • This approach ensures lifelong production of the enzyme.

• Woman X:
  • Normal thickening of the uterine wall due to regular hormonal activity.
• Woman Y:
  • Lack of thickening indicates hormonal imbalance or insufficient secretion of estrogen and progesterone.

• Biodiversity hotspots:
  • Regions with high species richness and endemic species but face significant habitat destruction.
  • Protecting these areas ensures species survival, maintains ecosystem stability, and preserves genetic resources for future use.

• Western Ghats.
• Indo-Burma region.

• Grazing Food Chain:
  • Begins with producers (plants) consumed by herbivores.
  • Example: Grass → Deer → Lion.
• Detritus Food Chain:
  • Begins with decomposers breaking down organic matter.
  • Example: Dead leaves → Fungi → Earthworms.

• Brood Parasitism: A reproductive strategy where one species lays its eggs in the nest of another species.
• Example: Cuckoo lays its eggs in crow nests, and cuckoo chicks often outcompete crow chicks for food.

• Garden Pea: F1 progeny exhibits complete dominance, showing the dominant flower color.
• Antirrhinum: F1 progeny exhibits incomplete dominance, resulting in an intermediate flower color (e.g., pink when red and white are crossed).

• Diagram should include:
  • Generative Cell.
  • Tube Cell.
  • Pollen Wall.
  • Pollen Grain.
• Functions:
  • Generative Cell: Divides to form two male gametes.
  • Tube Cell: Grows into a pollen tube to facilitate fertilization.

• Answer: Steroids.
• How they are consumed: Orally, injected, or applied topically depending on their formulation.
• Organ affected: Liver.

• Antibody Diagram: Should include:
  • Light Chain.
  • Heavy Chain.
  • Antigen Binding Site.
  • Disulfide Bond.
• Chemical Nature: Glycoproteins composed of polypeptide chains.
• Producing Cells: B-Lymphocytes or Plasma Cells.

• Transgenic animals are genetically modified to produce important biological substances like proteins, enzymes, and hormones.
• Example: Transgenic goats produce antithrombin, a protein used to treat blood clotting disorders.

• Transgenic animals are used as model organisms to study human diseases, their progression, and treatment.
• Example: Transgenic mice are used to study cancer, diabetes, and Alzheimer’s disease.

• Transgenic animals are used to test the safety and efficacy of chemicals and drugs before human use.
• Example: Toxicity testing using transgenic rodents ensures the safety of pharmaceuticals and other chemicals.

• A: Vector DNA.
• B: Foreign DNA.

The palindrome sequence recognized by EcoRI is:

5'-GAATTC-3'
3'-CTTAAG-5'

• EcoRI cuts between G and A in the sequence, generating sticky ends.
• Events that follow:
  • The sticky ends of vector DNA and foreign DNA pair through complementary base pairing.
  • DNA ligase seals the nicks, forming recombinant DNA.

• A symbiotic association between fungi and plant roots.
• Enhances water and nutrient absorption, particularly phosphorus.

• A cyanobacterium capable of nitrogen fixation.
• Provides nitrogen to plants in a usable form and enhances soil fertility.

• A bacterium that forms nodules on the roots of leguminous plants.
• Converts atmospheric nitrogen into ammonia, which is used by the plant.

• Skull A: Homo sapiens.
• Skull B: Neanderthals.
• Skull C: Australopithecus.
• More Similar: Skulls A and B (Homo sapiens and Neanderthals).

• (i) Ape-like: Australopithecus.
• (ii) Man-like: Homo erectus.

• RNA Product: Messenger RNA (mRNA).
• Enzyme: RNA Polymerase II.

• Process: Splicing.
• Explanation:
  • The pre-mRNA transcribed from DNA contains both coding (exons) and non-coding (introns) regions.
  • During splicing, introns are removed, and exons are joined to form a mature mRNA, which is translated into a protein.

• Prokaryotes: Have a single RNA polymerase.
• Eukaryotes: Have three RNA polymerases:
  • RNA Polymerase I: Synthesizes rRNA.
  • RNA Polymerase II: Synthesizes mRNA.
  • RNA Polymerase III: Synthesizes tRNA and some small RNAs.

• Prokaryotes: Transcription occurs in the cytoplasm.
• Eukaryotes: Transcription occurs in the nucleus.
• Explanation:
  • Prokaryotes lack a defined nucleus, so transcription occurs directly in the cytoplasm where translation can occur simultaneously.
  • Eukaryotes have a defined nucleus where transcription occurs, separating it from translation, which happens in the cytoplasm.

• Curve ‘A’: Exponential growth curve.
• Curve ‘B’: Logistic growth curve.

• The dotted line indicates the carrying capacity (K).
• Importance: Carrying capacity represents the maximum population size that an environment can sustain indefinitely. It depends on resource availability and environmental constraints.

• Curve ‘B’ (Logistic Growth): Accounts for environmental resistance, stabilizing population size as it approaches the carrying capacity.
• Curve ‘A’ (Exponential Growth): Assumes unlimited resources, which is unrealistic in natural environments.

• Curve ‘B’ (Logistic Growth): It reflects real-world conditions where resources are limited, and competition regulates population size.

• Exponential growth curve (Curve ‘A’): Relevant because human populations continue to grow rapidly due to advancements in healthcare and technology.
• However, environmental challenges may enforce a shift to a logistic growth model over time.

• The uterine lining sheds due to a drop in progesterone levels, resulting in menstrual bleeding.

• FSH stimulates the development of follicles, and estrogen levels increase, thickening the uterine lining.

• After ovulation, the ruptured follicle forms the corpus luteum, secreting progesterone to maintain the uterine lining for possible implantation.

• Identifies the fertile window for conception or avoiding pregnancy.
• Helps monitor reproductive health and detect irregularities.

• Reason: Endosperm development ensures a nutrient supply for the developing embryo.
• Role in albuminous seeds: In seeds like wheat and maize, the endosperm persists in mature seeds and provides nutrients during germination.

• Stages include globular, heart-shaped, torpedo, and mature embryo stages.
• Key structures: Cotyledons, Plumule (shoot tip), Radicle (root tip).

• Entry: HIV attaches to CD4 receptors on T-cells and fuses with the cell membrane.
• Reverse Transcription: Viral RNA is converted into DNA by reverse transcriptase.
• Integration: Viral DNA integrates into the host genome via integrase.
• Replication: Host cell machinery synthesizes viral proteins and RNA.
• Release: New viruses assemble and exit, destroying T-cells over time.
• Progression: Immune system weakens, leading to opportunistic infections and AIDS.

• Symptoms:
  • Recurring high fever with chills.
  • Sweating and shivering.
  • Headache and body aches.
  • Nausea and vomiting.
  • Fatigue and weakness.
• Cause: Symptoms are due to the release of merozoites into the bloodstream when red blood cells rupture. Haemozoin, a toxic substance, is released, triggering the immune response.

• Steps:
  • Gamete Formation: Gametocytes form in humans and are ingested by a mosquito.
  • Fertilization: Male and female gametocytes fuse in the mosquito's gut to form a zygote.
  • Ookinete Formation: The zygote develops into a motile ookinete, penetrating the gut wall.
  • Oocyst Development: The ookinete forms an oocyst on the mosquito’s gut wall.
  • Sporozoite Formation: The oocyst divides to produce sporozoites, which migrate to the salivary glands.
  • Completion: Sporozoites are injected into a new human host when the mosquito feeds.

• Polarity: 5’ to 3’.
• Additional Amino Acids: Determined by the number of untranslated codons remaining in the mRNA. Each codon translates to one amino acid until a stop codon is reached.

• Initiating Codon: AUG.
• Anticodon: UAC.
• Amino Acid: Methionine.

• Charging Process: tRNA is charged by attaching an amino acid using aminoacyl-tRNA synthetase.
• Purpose: A charged tRNA ensures the correct amino acid is added during translation, enabling accurate protein synthesis.

• Reason: Sickle-cell anaemia is named after the sickle-shaped red blood cells that appear under low oxygen levels.

• Cause: A point mutation in the β-globin gene replaces glutamic acid with valine in haemoglobin.
• Effect: Abnormal haemoglobin (HbS) polymerizes under low oxygen, deforming red blood cells.

• Parental Genotypes: HbA HbS (carriers).
• Child Genotypes: HbA HbA (normal), HbA HbS (carrier), HbS HbS (affected).
• Punnett Square: Shows a 25% probability of an affected child.