Section-A / Objective Type Questions
Question Nos 1 to 70 have four options, out of which only one is correct, You have to mark your selected option on the OMR Sheet. Answer any 35 questions. 35 x 1 = 35
Section-B / Short Answer Type Questions
Question Nos 1 to 20 are short Answer Type. Answer any 10 questions. Each question carries 2marks. 10 x 2 = 20
- What is polyembryony? Give two examples.
Polyembryony is the phenomenon where multiple embryos develop from a single fertilized egg or ovule.
Examples: Citrus fruits (e.g., orange) and certain gymnosperms (e.g., pine). - Define monosporic development of embryo sac.
Monosporic development is the formation of the embryo sac from a single megaspore (out of four produced by meiosis), where the other three megaspores degenerate. It is the most common type in angiosperms (e.g., Polygonum type). - Where are Leydig or interstitial cells found and what is their role?
Leydig cells are found in the interstitial tissue between the seminiferous tubules in the testes.
Their role is to produce and secrete testosterone (androgens) in response to luteinizing hormone (LH). - What is ZIFT?
ZIFT (Zygote Intrafallopian Transfer) is an assisted reproductive technique where eggs are fertilized in vitro with sperm, and the resulting zygote is transferred into the fallopian tube. - What is Chromosomal theory of inheritance?
The chromosomal theory of inheritance states that genes are located on chromosomes, and the behavior of chromosomes during meiosis explains Mendel's laws of segregation and independent assortment. It was proposed by Sutton and Boveri. - Define homology and give example of homologous organs.
Homology is the similarity in structure and origin of organs due to common ancestry, despite different functions.
Example: Forelimbs of vertebrates (human arm, bat wing, whale flipper, horse leg). - Name pentose sugar and nitrogenous bases found in RNA.
Pentose sugar: Ribose.
Nitrogenous bases: Adenine (A), Guanine (G), Cytosine (C), Uracil (U). - What are parts of transcription unit? Define them.
A transcription unit consists of three parts:
- Promoter: DNA sequence where RNA polymerase binds to initiate transcription.
- Structural gene: The segment that is transcribed into RNA.
- Terminator: Sequence that signals the end of transcription. - What is the meaning of charging of tRNA?
Charging of tRNA (aminoacylation) is the process where a specific amino acid is attached to its corresponding tRNA by aminoacyl-tRNA synthetase, using ATP energy, preparing it for protein synthesis. - Name three species of Plasmodium causing malaria. Which species of Plasmodium causes malignant malaria?
Three species: Plasmodium vivax, Plasmodium falciparum, Plasmodium malariae.
Plasmodium falciparum causes malignant (tertian) malaria. - What are interferons? What is their role?
Interferons are signaling proteins (cytokines) produced and released by cells in response to viral infections.
Their role is to interfere with viral replication, activate immune cells, and enhance antiviral defenses in neighboring cells. - Define primary lymphoid organs. What are their names?
Primary lymphoid organs are sites where lymphocytes (B and T cells) mature and acquire antigen-specific receptors.
Names: Bone marrow (for B cells) and thymus (for T cells). - What is the source of statin? Write its use.
Statins are derived from fungi (e.g., Aspergillus terreus for lovastatin) or synthesized chemically.
Use: To lower blood cholesterol levels by inhibiting HMG-CoA reductase, reducing risk of cardiovascular diseases. - Define Plasmid.
A plasmid is a small, circular, double-stranded DNA molecule found in bacteria (and some eukaryotes) that replicates independently of the chromosomal DNA and often carries accessory genes (e.g., for antibiotic resistance). - What is the use of PCR? Write down name of steps involved in it only.
Uses: Amplification of DNA for cloning, diagnostics, forensics, and research.
Steps: Denaturation, Annealing, Extension (Elongation). - What is BT Cotton?
Bt cotton is genetically modified cotton incorporating genes from Bacillus thuringiensis (Bt) bacterium, which produce toxins lethal to bollworm pests, making the plant pest-resistant. - What is competitive exclusion principle?
The competitive exclusion principle states that two species competing for the same limited resources cannot coexist indefinitely; one will outcompete and eliminate the other. - Define primary productivity?
Primary productivity is the rate at which producers (autotrophs) convert solar energy into chemical energy (biomass) through photosynthesis or chemosynthesis. - What is in situ conservation? What are the main methods of such conservation?
In situ conservation is the protection of species in their natural habitats.
Main methods: National parks, wildlife sanctuaries, biosphere reserves, and protected areas. - What is rivet popper hypothesis?
The rivet popper hypothesis (by Paul Ehrlich) compares species in an ecosystem to rivets in an airplane: loss of some species (rivets) may not immediately affect function, but excessive loss weakens the ecosystem; loss of key species is especially critical.
Section-C / Long Answer Type Questions
Question Nos 21 to 26 are Long Answer Type. Answer any three questions. Each question carries 5 marks. 3 x 5 = 15
- Explain the reasons of loss of biodiversity.
Loss of biodiversity is mainly caused by human activities and natural factors. The major reasons are often remembered by the acronym HIPPO:
- Habitat loss and fragmentation: Deforestation, urbanization, agriculture, mining, and infrastructure development destroy or fragment natural habitats.
- Invasive species: Introduction of alien species that compete with, prey upon, or bring diseases to native species.
- Pollution: Air, water, soil, and noise pollution affect survival and reproduction of species.
- Population (Human overpopulation): Increased demand for resources leads to overexploitation.
- Overexploitation: Overhunting, overfishing, and excessive harvesting of plants and animals.
- Other factors: Climate change causing shifts in habitats, and natural disasters (though minor compared to anthropogenic causes).
- What is gene therapy? Describe first case of clinical gene therapy.
Gene therapy is a therapeutic technique in which a functional gene is introduced into the cells of a patient to correct a genetic disorder caused by a defective or missing gene.
It can be ex vivo (cells removed, treated, and returned) or in vivo (direct delivery into body).
First clinical gene therapy case:
In September 1990, a 4-year-old girl named Ashanti DeSilva suffering from Adenosine Deaminase (ADA) deficiency (a severe combined immunodeficiency disorder) was treated at NIH, USA, by Dr. W. French Anderson and team.
Her T-lymphocytes were removed, transfected with a normal ADA gene using a retroviral vector (ex vivo), and reintroduced into her body.
The therapy was partially successful; she showed improvement but required periodic treatments. - Explain differences between any two –
1. Innate Immunity and Acquired Immunity
- Innate immunity is present from birth, non-specific, and provides immediate first-line defense (e.g., skin, mucus, phagocytes, fever).
- Acquired immunity develops after exposure to antigen, is highly specific, has memory, and provides long-term protection (involves B and T lymphocytes).
- Innate has no memory, while acquired shows immunological memory.
- Innate response is rapid but same on repeated exposure; acquired response is slower initially but stronger and faster on subsequent exposure.
- Active immunity develops when the person's own immune system produces antibodies after exposure to antigen (natural: infection; artificial: vaccination). It is long-lasting with memory.
- Passive immunity involves direct transfer of pre-formed antibodies (natural: maternal antibodies via placenta/colostrum; artificial: antisera/injection of immunoglobulins). It is immediate but short-lived with no memory.
- What is genetic code? Describe its salient features.
Genetic code is the sequence of nucleotides (triplets or codons) in mRNA that specifies the sequence of amino acids in a polypeptide during translation.
Salient features:
- Triplet nature: Each codon consists of three nucleotides (64 codons for 20 amino acids + 3 stop codons).
- Degeneracy/Redundancy: Most amino acids are coded by more than one codon (e.g., leucine by 6 codons).
- Universality: Same in almost all organisms (few exceptions like mitochondria).
- Non-overlapping and commaless: Codons are read sequentially without overlapping or gaps.
- Start and stop codons: AUG is initiation codon (codes for methionine); UAA, UAG, UGA are termination codons.
- Non-ambiguous: Each codon specifies only one amino acid.
- Describe spermatogenesis. Explain roles of hormones also.
Spermatogenesis is the process of formation of mature spermatozoa from spermatogonia in the seminiferous tubules of testes.
Stages:
- Multiplication phase: Spermatogonia (2n) divide mitotically to form primary spermatocytes (2n).
- Growth phase: Primary spermatocytes undergo growth.
- Maturation phase: Primary spermatocytes undergo meiosis I → secondary spermatocytes (n); meiosis II → spermatids (n).
- Spermiogenesis: Spermatids transform into spermatozoa (sperm) by losing cytoplasm, forming acrosome, condensing nucleus, and developing tail.
- FSH (Follicle Stimulating Hormone): Stimulates Sertoli cells, which provide nourishment and support to developing germ cells.
- LH (Luteinizing Hormone): Stimulates Leydig cells to secrete testosterone.
- Testosterone: Essential for spermatogenesis, promotes maturation of germ cells and development of male characteristics.
- GnRH from hypothalamus regulates FSH and LH secretion.
- Write short notes on any two –
i. Types of pollination
Pollination is the transfer of pollen grains from anther to stigma.
Types:
- Self-pollination (Autogamy): Pollen from same flower or same plant transferred to stigma (e.g., pea). Ensures seed set but reduces genetic variation.
- Cross-pollination (Allogamy): Pollen from one flower transferred to stigma of another flower on different plant of same species. Promotes genetic diversity.
- Agents: Anemophily (wind), Hydrophily (water), Entomophily (insects), Ornithophily (birds), Chiropterophily (bats).
Double fertilisation is a unique process in angiosperms discovered by Nawaschin (1898).
One male gamete fuses with egg cell → zygote (2n) → embryo.
Second male gamete fuses with two polar nuclei → primary endosperm nucleus (3n) → endosperm (nutritive tissue).
It ensures that endosperm develops only after fertilisation (economy of resources) and is characteristic of flowering plants.
iii. Pleiotropy
Pleiotropy is the phenomenon where a single gene influences multiple, seemingly unrelated phenotypic traits.
Example: In humans, the gene for phenylketonuria (PKU) causes mental retardation, reduced skin/hair pigmentation, and other symptoms due to accumulation of phenylalanine.
Another example: In sickle cell anaemia, the mutant haemoglobin gene causes sickling of RBCs, anaemia, and resistance to malaria.
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