DHR - BRET PYQs Sept 2022

Immunology & Molecular Biology

Sebaceous glands secrete through which mode of secretion?

Sebaceous glands associated with hair follicles secrete sebum via holocrine mode where entire cell disintegrates to release lipid-rich product. Accumulated sebum lubricates skin and hair. Merocrine releases via exocytosis without loss, apocrine pinches apical cytoplasm, unlike holocrine complete rupture.

Ref: Ross Michael H., Pawlina Wojciech, Histology A Text and Atlas, 7th Edition, Chapter 15 Integumentary System, explains sebaceous gland holocrine secretion mode involving whole cell disintegration versus merocrine and apocrine mechanisms for sebum release, published by Wolters Kluwer Lippincott Williams and Wilkins.

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Immunology & Molecular Biology

Which of the following is the glycoprotein layer surrounding oocyte?

Zona pellucida is translucent extracellular matrix composed of ZP1, ZP2, ZP3 sulfated glycoproteins surrounding mammalian oocyte inside cumulus. It mediates species-specific sperm binding, triggers acrosome reaction, blocks polyspermy and protects preimplantation embryo until hatching.

Ref: Alberts Bruce, Johnson Alexander, Lewis Julian, Morgan David, Raff Martin, Roberts Keith, Walter Peter, Molecular Biology of the Cell, 6th Edition, Chapter 20 Fertilization, describes zona pellucida glycoprotein matrix ZP1 ZP2 ZP3 around oocyte sperm binding and polyspermy block, published by Garland Science.

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Immunology & Molecular Biology

The male reproductive tract develops from:

In male embryos, testosterone stabilizes mesonephric Wolffian ducts which differentiate into epididymis, vas deferens and seminal vesicles. Anti-Mullerian hormone causes regression of Mullerian paramesonephric ducts. Female tract conversely retains Mullerian derivatives, demonstrating hormone-dependent duct fate.

Ref: Moore Keith L., Persaud T.V.N., Torchia Mark G., The Developing Human Clinically Oriented Embryology, 11th Edition, Chapter 12 Urogenital System, explains Wolffian mesonephric duct forming male tract epididymis vas deferens under testosterone and Mullerian regression, published by Elsevier.

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Immunology & Molecular Biology

Which one of the following is a marine fish?

Rohu, Catla and Common carp are freshwater Indian major carps cultured in ponds. Hilsa ilisha, belonging to Clupeidae, is anadromous but predominantly marine, inhabiting Bay of Bengal and migrating to rivers for breeding, hence classified as marine fish economically important.

Ref: Jhingran V.G., Fish and Fisheries of India, Revised 1991 Edition, Chapter 6 Commercial Marine and Freshwater Fishes, details Rohu Catla common carp as freshwater carps and Hilsa as marine anadromous clupeid fishery importance, published by Hindustan Publishing Corporation.

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Immunology & Molecular Biology

Which one of the following is a breed of cattle?

Ayrshire is a recognized dairy cattle breed originating from Ayrshire, Scotland, known for high milk yield, reddish-brown spots and hardiness. Ghagus and Kadaknath are poultry breeds, Scampi denotes prawn, thus cattle identification relies on breed registry classifications.

Ref: Banerjee Gautam C., A Textbook of Animal Husbandry, 8th Edition, Chapter 5 Cattle Breeds, describes Ayrshire as exotic dairy cattle breed characteristics origin productivity versus indigenous breeds and poultry breeds Ghagus Kadaknath, published by Oxford and IBH Publishing.

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Immunology & Molecular Biology

Which of the following reproduces sexually only once in its life time?

Monocarpic plants flower and set seed once before senescence, investing accumulated resources into single reproductive event. According to given key, tomato is considered in this category within this question set, contrasting with polycarpic perennials like mango and eucalyptus that reproduce repeatedly over many seasons.

Ref: Raven Peter H., Evert Ray F., Eichhorn Susan E., Biology of Plants, 8th Edition, Chapter 19 Reproductive Strategies, explains monocarpic versus polycarpic life histories, annuals flowering once, perennials reproducing repeatedly, resource allocation concepts, published by W.H. Freeman.

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Immunology & Molecular Biology

Long plants are able to stand erect due to presence of:

Tall plants resist gravity and wind through mechanical tissues. Sclerenchyma fibres and sclereids possess heavily lignified secondary walls providing tensile strength and rigidity after cell death. Collenchyma offers flexible support in young organs, but prolonged erect habit depends on sclerenchyma.

Ref: Esau Katherine, Evert Ray F., Esau's Plant Anatomy, 3rd Edition, Chapter 8 Sclerenchyma, discusses lignified secondary walls, mechanical support, tall plant erect habit due to sclerenchyma fibres versus collenchyma and parenchyma, published by Wiley Interscience.

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Immunology & Molecular Biology

Hormone responsible for growth of the root in micropropagation is:

In plant tissue culture, cytokinin to auxin ratio determines organogenesis. High auxin promotes root initiation by inducing dedifferentiation, activating root meristem genes, stimulating pericycle divisions and lateral root primordia formation. Auxins like NAA, IBA are routinely used for rooting microshoots.

Ref: Bhojwani Sant S., Dantu Prem Kumar, Plant Tissue Culture An Introductory Text, Edition 2013, Chapter 5 Organogenesis and Micropropagation, discusses auxin cytokinin ratio, auxin role in root induction and rooting of shoots, published by Springer India.

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Immunology & Molecular Biology

Which one of the following is an example for homology?

Homologous structures originate from common ancestral organ but diverge functionally. Thorn of Bougainvillea and tendril of Cucurbita both are modified axillary stems with similar vascular anatomy and developmental origin, despite protective versus climbing roles, demonstrating divergent evolution, unlike analogous eye or wings.

Ref: Campbell Neil A., Reece Jane B., Biology, 11th Edition, Chapter 22 Descent with Modification, explains homology versus analogy, thorns of Bougainvillea and tendrils of Cucurbita as homologous modified stems demonstrating divergent evolution, published by Pearson.

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Immunology & Molecular Biology

Kranz anatomy occurs in:

Kranz anatomy characterizes C4 plants where bundle sheath cells surround vascular bundles in wreath-like arrangement, containing centripetally arranged chloroplasts. Mesophyll cells fix CO2 into C4 acids transported to sheath for Calvin cycle, minimizing photorespiration, predominantly in leaves.

Ref: Taiz Lincoln, Zeiger Eduardo, Møller Ian Max, Plant Physiology and Development, 6th Edition, Chapter 8 Photosynthesis C4 Pathway, describes Kranz anatomy in leaves, bundle sheath and mesophyll dimorphism in C4 plants, published by Sinauer Associates.

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Immunology & Molecular Biology

Which of the following is used as an atmospheric pollution indicator?

Lichens lack roots and absorb nutrients directly from air, making them highly sensitive to SO2, NOx and heavy metals which bleach chlorophyll and inhibit photosynthesis. Their absence in polluted urban areas and diversity indices therefore reliably indicate air quality and atmospheric pollutant loads.

Ref: Begon Michael, Townsend Colin R., Harper John L., Ecology From Individuals to Ecosystems, 4th Edition, Chapter 15 Pollution Ecology, details lichens as bioindicators of air pollution, sensitivity to sulfur dioxide and heavy metals, published by Wiley-Blackwell.

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Immunology & Molecular Biology

Fossils are generally found in:

Igneous rocks form from molten magma at temperatures destroying organic remains, metamorphic rocks undergo intense heat pressure similarly degrading fossils. Sedimentary rocks form by deposition and lithification at low temperatures, preserving organisms in strata, thus providing primary archive of paleontological record.

Ref: Press Frank, Siever Raymond, Understanding Earth, 7th Edition, Chapter 3 Sedimentary Rocks and Fossil Preservation, explains why fossils are preserved almost exclusively in sedimentary rocks versus igneous metamorphic destruction, published by W.H. Freeman and Company.

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