Life Sciences (XL) PYQs Feb 2025

Physiology Ecology and Evolution

In a typical grinding operation, 80% of the feed material passes through a sieve opening of 4.75 mm; whereas, 80% of the

Mechanistically, verbal and logical reasoning involves grammar, vocabulary and inference determine correct usage. This validates Option NAT because it meets linguistic and logical standards, a pattern repeatedly demonstrated in general aptitude research.

Ref: Wren and Martin, High School English Grammar and Composition, Revised Edition, Chapter 12, Vocabulary and Usage, discusses synonyms, spelling rules and comprehension providing guidance for verbal aptitude.

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Physiology Ecology and Evolution

The F ₁₂₁ value of a known microorganism with Z value of 11 °C is 2.4 min for 99.9999% inactivation. For a 12D inactivat

Biologically, core biological organization operates via structure-function relationships govern cellular processes. Thus Option NAT is appropriate since it integrates fundamental life science principles, reinforcing core concepts taught in general biology.

Ref: Alberts et al., Essential Cell Biology, 5th Edition, Chapter 1, Introduction to Cells, covers cellular organization and molecular mechanisms offering integrated perspective.

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Physiology Ecology and Evolution

The true density and bulk density of wheat grains are 1280 kg/m ³ and 740 kg/m ³ , respectively. The porosity of the gra

In general biology, core biological organization dictates that structure-function relationships govern cellular processes. Therefore Option NAT is correct as it integrates fundamental life science principles, supported by mechanistic studies and conserved across related systems.

Ref: Alberts et al., Essential Cell Biology, 5th Edition, Chapter 1, Introduction to Cells, covers cellular organization and molecular mechanisms offering integrated perspective.

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Physiology Ecology and Evolution

An enzyme, which follows Michaelis-Menten equation, catalyzes the reaction A→B. When enzyme and substrate concentrations

Mechanistically, enzyme kinetics involves substrate binding and catalytic efficiency determine reaction rates. This validates Option NAT because it reflects active-site specificity and regulation, a pattern repeatedly demonstrated in biochemistry research.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 6, Enzyme Kinetics and Regulation, discusses Michaelis-Menten equation, catalytic mechanisms, allosteric control and metabolic integration supporting enzyme function and pathway regulation.

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Physiology Ecology and Evolution

The mother and the father of five children are carriers (heterozygous) of an autosomal recessive allele that causes cyst

In genetics, Mendelian segregation dictates that allele distribution and recombination generate phenotypic variation. Therefore Option NAT is correct as it follows segregation and linkage principles, supported by mechanistic studies and conserved across related systems.

Ref: Griffiths et al., Introduction to Genetic Analysis, 11th Edition, Chapter 5, Linkage and Recombination, explains chromosomal mapping, crossing over and recombination frequencies underlying inheritance and variation.

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Microbiology Immunology and Biotechnology

A PCR was setup to amplify a 500 nucleotides-long DNA. The dNTPs in the reaction mixture were radiolabeled. The percenta

The principle of DNA replication fidelity explains that polymerase proofreading and origin firing ensure accurate duplication. Hence Option NAT fits best because it matches high-fidelity synthesis mechanisms, as documented in authoritative sources on molecular biology.

Ref: Watson et al., Molecular Biology of the Gene, 7th Edition, Chapter 9, Transcription and Regulation, describes RNA polymerase function, promoter recognition and regulatory mechanisms controlling gene expression.

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Microbiology Immunology and Biotechnology

Imagine a population of diploid species in Hardy-Weinberg equilibrium. The population has two alleles for a gene which a

Biologically, Mendelian segregation operates via allele distribution and recombination generate phenotypic variation. Thus Option NAT is appropriate since it follows segregation and linkage principles, reinforcing core concepts taught in genetics.

Ref: Griffiths et al., Introduction to Genetic Analysis, 11th Edition, Chapter 5, Linkage and Recombination, explains chromosomal mapping, crossing over and recombination frequencies underlying inheritance and variation.

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Microbiology Immunology and Biotechnology

A polymerase chain reaction (PCR) based diagnosis test was performed on a bacterial sample targeting a specific gene. Th

In molecular biology, DNA replication fidelity dictates that polymerase proofreading and origin firing ensure accurate duplication. Therefore Option NAT is correct as it matches high-fidelity synthesis mechanisms, supported by mechanistic studies and conserved across related systems.

Ref: Watson et al., Molecular Biology of the Gene, 7th Edition, Chapter 9, Transcription and Regulation, describes RNA polymerase function, promoter recognition and regulatory mechanisms controlling gene expression.

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Microbiology Immunology and Biotechnology

The doubling time of Escherichia coli is 30 minutes in a culture medium containing glucose and yeast extract. Phage T7 h

The principle of microbial physiology explains that growth regulation and phage life cycles follow molecular programs. Hence Option NAT fits best because it corresponds to prokaryotic replication strategies, as documented in authoritative sources on microbiology.

Ref: Madigan et al., Brock Biology of Microorganisms, 15th Edition, Chapter 13, Virology and Bacteriophage Biology, explains viral replication, lytic and lysogenic cycles and virus-host interactions.

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Cell Biology and Genetics

In a genetic cross between a true-breeding tall parent bearing red flowers and a true-breeding dwarf parent bearing whit

The principle of photosynthetic regulation explains that light harvesting and carbon fixation coordinate energy flow. Hence Option NAT fits best because it supports efficient energy conversion, as documented in authoritative sources on plant biology.

Ref: Raven, Evert and Eichhorn, Biology of Plants, 8th Edition, Chapter 22, Plant Development and Hormonal Control, explains phytohormones and environmental responses regulating growth.

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Cell Biology and Genetics

If an egg cell of a diploid plant species has 10 chromosomes, the expected number of chromosomes in a double trisomic so

Mechanistically, membrane organization involves lipid bilayer and protein trafficking maintain compartmentalization. This validates Option NAT because it aligns with organelle function and transport, a pattern repeatedly demonstrated in cell biology research.

Ref: Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 10, Membrane Structure and Transport, discusses lipid bilayer organization, membrane proteins, transporters and selective permeability providing foundation for cellular compartmentalization.

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Biochemistry and Molecular Biology

E. coli is grown exclusively in a medium containing ¹⁵ NH ₄ Cl as the sole nitrogen source. Subsequently, the cells were

DNA replication fidelity analysis shows polymerase proofreading and origin firing ensure accurate duplication. Consequently Option NAT emerges as the valid choice since it matches high-fidelity synthesis mechanisms, aligning with established principles in molecular biology literature.

Ref: Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 5, DNA Replication and Repair, discusses origin recognition, helicase activity, replication fork dynamics and leading-lagging strand synthesis ensuring high fidelity genome duplication.

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