• 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.

• 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.

• 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.

• 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.

• Correct Answer: (B) Evening primrose
• Solution: Hugo de Vries observed sudden heritable changes (mutations) while working with the evening primrose plant (Oenothera lamarckiana). His mutation theory proposed that these sudden changes serve as the basis for evolution, introducing new traits into populations.

• Correct Answer: (C) (iii) (ii) (iv) (i)
• Solution: The correct matches between the organisms and the products they produce are:
  • Lactobacillus – Cheese
  • Saccharomyces cerevisiae – Curd
  • Aspergillus niger – Citric acid
  • Acetobacter aceti – Acetic acid

• Correct Answer: (B) A – III, B – I, C – IV, D – II
• Solution:
  • A. The pill – III. Inhibits ovulation
  • B. Condom – I. Prevent sperm reaching cervix
  • C. Vasectomy – IV. Semen contains no sperm
  • D. Copper-T – II. Prevent implantation

• Correct Answer: (C) Ovum – A, Morula – E, Blastocyst – G
• Solution: Based on the stages of development in the female reproductive system:
  • Ovum (A): The unfertilized egg
  • Morula (E): The solid mass of cells resulting from cleavage of the fertilized egg
  • Blastocyst (G): The structure that implants into the uterine wall for further development

• Correct Answer: (C) BAC and YAC
• Solution: BAC (Bacterial Artificial Chromosome) and YAC (Yeast Artificial Chromosome) were used as vectors in the Human Genome Project due to their capacity to clone large fragments of DNA efficiently.

• Correct Answer: (A) Aneuploidy
• Solution: Turner’s syndrome is a chromosomal disorder caused by the presence of only one X chromosome in females (45, X). This is an example of aneuploidy, which refers to the presence of an abnormal number of chromosomes.

• Correct Answer: (B) Antigen-antibody interaction
• Solution: ELISA (Enzyme-Linked Immunosorbent Assay) detects and quantifies antigens or antibodies using the principle of antigen-antibody interaction. This method is widely used for diagnostic purposes in medical and research fields.

• Correct Answer: (D) Restriction enzymes
• Solution: Restriction enzymes, also known as molecular scissors, cut DNA at specific sequences called recognition sites. These enzymes are essential tools in genetic engineering and molecular biology.

• Correct Answer: (C) (A) is true, but (R) is false
• Solution: Plasmids are autonomously replicating circular DNA molecules found in prokaryotic cells, not eukaryotic cells. These plasmids are widely used as vectors in genetic engineering.

• Correct Answer: (A) Both (A) and (R) are true and (R) is the correct explanation of (A)
• Solution: The mutualistic relationship between figs and fig wasps involves the wasp pollinating the fig flowers while depositing eggs. This ensures species-specific pollination.

• Correct Answer: (B) Both (A) and (R) are true and (R) is not the correct explanation of (A)
• Solution: Inverted biomass pyramids occur in aquatic ecosystems because the biomass of primary producers (phytoplankton) is smaller but reproduces rapidly, supporting higher trophic levels. The reason provided is true, but it is not the correct explanation for inverted biomass pyramids. Energy typically decreases with increasing trophic levels, but rapid reproduction of primary producers compensates for their low biomass.

• Correct Answer: (A) Both (A) and (R) are true and (R) is the correct explanation of (A).
• Solution: Patents are legal rights granted to inventors to protect their innovations, preventing unauthorized commercial use by others. The reason correctly explains the assertion.

• Correct Answer: Rosie
• Solution: Rosie was the first transgenic cow developed in 1997. It produced milk enriched with human protein (alpha-lactalbumin), making it more nutritionally suitable for infants.

• Correct Answer: The milk contained human alpha-lactalbumin.
• Solution: Rosie’s milk was enriched with human alpha-lactalbumin, making it nutritionally superior. This milk provided essential proteins required for infant growth and development.

• Correct Answer: Woman ‘X’ indicates pregnancy; Woman ‘Y’ indicates no pregnancy.
• Solution:
  • In woman ‘X,’ the uterine wall continues to thicken after ovulation, indicating successful implantation and pregnancy.
  • In woman ‘Y,’ the uterine wall thickness reduces after ovulation, indicating no fertilization, leading to menstruation.

• Correct Answer:
  1. Unprotected sexual contact.
  2. Sharing of contaminated needles.

• Correct Answer: Early detection helps in timely treatment and prevents disease progression.
• Solution:
  • HIV and Hepatitis-B can spread through unprotected sexual contact, blood transfusion, or contaminated syringes.
  • Early detection helps in timely management, reduces transmission risk, and improves patient outcomes.

• Correct Answer: Biodiversity hotspots have high species richness and endemic species. Protecting these areas prevents habitat destruction and species extinction.
• Solution:
  • Biodiversity hotspots are regions with a high level of species richness and endemic species under threat due to human activities.
  • Protection efforts such as habitat restoration, creating reserves, and sustainable practices help in preserving these species.

• Correct Answer:
  1. Western Ghats
  2. Indo-Burma region

• Correct Answer:
  • Grazing food chain:
    • Starts with living plants (producers) that are consumed by herbivores (primary consumers).
    • Example: Grass → Grasshopper → Frog → Snake.
  • Detritus food chain:
    • Begins with dead organic matter (detritus) that is consumed by decomposers (detritivores) like fungi and bacteria.
    • Example: Dead leaves → Earthworm → Bird.

• Correct Answer: Brood parasitism is when a bird lays its eggs in the nest of another bird species, letting the host bird incubate and raise its young. Example: Cuckoo lays eggs in the crow’s nest.
• Solution: Brood parasitism involves one species, like the cuckoo, exploiting another species (e.g., crow) to raise its offspring. The parasitic bird’s eggs mimic the host’s eggs to avoid detection.

Figure 1: Schematic diagram of the E.coli vector pBR322 with marked features.

• ori: Origin of replication.
• rop: Codes for proteins to regulate plasmid replication.
• Ampicillin-resistant gene: Labeled as 'ampR'.
• Tetracycline-resistant gene: Labeled as 'tetR'.
• Restriction site BamHI: Located at a specific position on the vector.
• Restriction site EcoRI: Located at a specific position on the vector.

• Correct Answer: Agrobacterium tumefaciens is used to transfer nematode-specific genes into tobacco plants, producing RNA interference (RNAi) that silences the gene responsible for infestation.
• Solution:
  • A nematode-specific gene is introduced into the tobacco plant using Agrobacterium tumefaciens.
  • The plant produces double-stranded RNA (dsRNA), initiating RNA interference (RNAi).
  • RNAi silences the vital genes of Meloidogyne incognita, reducing infestation and damage.

• Correct Answer: Flocs: Aggregates of bacteria and fungi that degrade organic matter during the secondary treatment of sewage.
• Solution:
  • Flocs are masses of aerobic bacteria and fungi that degrade organic matter, reducing Biochemical Oxygen Demand (BOD) in sewage water.

• Correct Answer: Anaerobic sludge digester: Breaks down organic matter in sludge into biogas and stabilizes waste.
• Solution:
  • The anaerobic sludge digester processes the settled sludge from the primary treatment under anaerobic conditions, producing biogas (methane, carbon dioxide) as a by-product.

• Correct Answer:
  • (A) Ape-like.
  • (B) Man-like.
  • (C) Similar to humans.
  • Skulls (B) and (C) are more similar to each other.

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

• Correct Answer: Steroids.
• Solution: Steroids are a group of lipophilic compounds with a characteristic four-ring structure, widely used in medicine as anti-inflammatory and hormonal drugs.

• Correct Answer: Steroids are usually consumed orally, injected, or applied topically, depending on their type and purpose.

• Correct Answer: Liver.
• Solution: The liver metabolizes steroids. Long-term or excessive use can damage the liver and other organs.

• Correct Answer:
  • Diagram: Antibody structure with labeled parts (e.g., heavy chain, light chain, antigen-binding site, disulfide bonds).
  • Chemical nature: Antibodies are glycoproteins.
  • Produced by: B-lymphocytes.

• Correct Answer: This represents a monohybrid cross, where the purple flower trait is dominant over the white flower trait.
• Solution:
  • The first generation (F1) produced only purple-flowered plants because purple is dominant.
  • In the second generation (F2), the ratio of purple to white flowers is approximately 3:1.

  		P: PP (purple) × pp (white)
  		F1: All Pp (purple)
  
  		F2 generation cross:
  		P p × P p gives: PP, Pp, Pp, pp.
  
  		Phenotypic ratio: 3 (purple):1 (white).
  		

• Correct Answer:
  • Diagram: Microspore with labeled parts (e.g., vegetative nucleus, generative nucleus, exine, intine).
  • Functions:
    • Vegetative nucleus: Controls pollen tube growth.
    • Generative nucleus: Divides to form two male gametes for fertilization.

• Correct Answer:
  • RNA product: mRNA.
  • Enzyme: RNA polymerase II.
• Explanation: mRNA is transcribed from DNA and carries the genetic information for protein synthesis. RNA polymerase II is responsible for transcribing protein-coding genes in eukaryotes.

• Correct Answer: RNA splicing.
• Solution:
  • Introns (non-coding regions) are removed, and exons (coding regions) are joined to form a mature mRNA strand.
  • This process reduces the RNA length to 1200 nucleotides, ready for translation.

• Correct Answer:
  • Prokaryotes: One RNA polymerase.
  • Eukaryotes: Three RNA polymerases (RNA polymerase I, II, and III).

• Correct Answer:
  • Prokaryotes: Transcription occurs in the cytoplasm.
  • Eukaryotes: Transcription occurs in the nucleus.
• Explanation: The separation of transcription and translation in eukaryotes allows for RNA processing, which is absent in prokaryotes.

• 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.

• Correct Answer: Growth curve ‘B’ considers environmental resistance (e.g., resource availability, competition), which limits population growth, unlike curve ‘A’.

• 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.

• Correct Answer:
  • Polarity: 5′ to 3′.
  • Number of amino acids: 4 amino acids.
• Reason: Translation proceeds in the 5′ to 3′ direction, and the remaining codons in the segment can accommodate 4 amino acids.

• Correct Answer:
  • Initiating codon: AUG.
  • Anticodon: UAC (on tRNA).
  • Amino acid: Methionine.

• Correct Answer:
  • Charging of tRNA (adaptor molecule): The process involves attaching a specific amino acid to its corresponding tRNA with the help of the enzyme aminoacyl-tRNA synthetase and ATP.
  • Need for charging: Charged tRNA delivers the correct amino acid to the ribosome during protein synthesis.
• Explanation: Charged tRNA ensures the fidelity of translation by accurately matching amino acids to their corresponding codons on the mRNA strand.

• Correct Answer: Sickle-cell anaemia is named after the sickle-shaped red blood cells observed in affected individuals, caused by abnormal haemoglobin.

• Correct Answer: The disorder is caused by a point mutation in the β-globin gene, resulting in the substitution of glutamic acid with valine at the sixth position of the haemoglobin molecule.
• Explanation: This mutation causes haemoglobin molecules to polymerize under low oxygen conditions, leading to the characteristic sickle shape of red blood cells.

• Correct Answer:

  		Parental Genotype: Both parents are carriers (HbA HbS).
  
  		Punnett Square:
  
  		      HbA     HbS
  		HbA   HbAHbA  HbAHbS
  		HbS   HbAHbS  HbSHbS
  
  		Results:
  		• 25% normal (HbAHbA).
  		• 50% carriers (HbAHbS).
  		• 25% sickle-cell anaemic (HbSHbS).
  		

• Entry and Integration: The virus enters the host body and attaches to CD4 receptors on helper T-cells. It injects its RNA and viral enzymes into the host cell.
• Reverse Transcription: Viral RNA is converted into DNA by reverse transcriptase.
• Integration: The viral DNA integrates into the host genome with the help of integrase enzyme.
• Replication and Assembly: The host cell machinery is used to produce viral RNA and proteins. New viruses are assembled.
• Release and Maturation: Newly formed viruses bud off from the host cell, ready to infect other cells. Over time, the number of helper T-cells decreases, leading to immune system failure (AIDS).

• Symptoms: Fever, chills, sweating, headache, muscle pain, and fatigue.
• Cause: Malaria is caused by Plasmodium parasites. These parasites infect red blood cells, causing their rupture and the release of toxins into the bloodstream.

• Gametocytes: Male and female gametocytes are ingested by a mosquito during a blood meal.
• Fertilization: Gametocytes fuse in the mosquito’s gut to form a zygote.
• Development: The zygote develops into an ookinete, which penetrates the gut wall and forms an oocyst.
• Sporozoites: The oocyst releases sporozoites that migrate to the mosquito’s salivary glands, ready to infect a new host.

• Objective: To obtain desired traits such as disease resistance, higher yield, or improved quality in plants by crossing two genetically different plants.

• Emasculation: Removal of stamens from the bisexual flowers of the female parent to prevent self-pollination.
• Bagging: Covering the emasculated flower with a bag to prevent contamination from unwanted pollen.
• Pollination: Dusting pollen from the male parent onto the stigma of the female parent.
• Re-bagging: Re-covering the flower to ensure fertilization occurs without external interference.

• Development: The placenta develops from the chorionic villi of the embryo and the uterine tissue of the mother. It establishes a structural and functional connection between the fetus and the mother.

• Functions:
  • Facilitates exchange of nutrients, gases, and waste products between the mother and fetus.
  • Produces hormones such as hCG, progesterone, and estrogens to maintain pregnancy.
  • Acts as a barrier to certain harmful substances while allowing essential nutrients to pass through.