Biochemistry & Agriculture

Biochemistry & Agriculture

The chemical test that is used for diagnosis of typhoid is:

Widal test detects Salmonella Typhi O and H agglutinins in patient serum through tube agglutination with killed antigens. Rising titre indicates enteric fever, though interpretation requires clinical correlation due to cross-reactivity and endemic baseline antibodies.

Ref: Ananthanarayan and Paniker, Textbook of Microbiology, 11th Edition, Chapter 33 Enterobacteriaceae and Serology, describes Widal test as tube agglutination test detecting O and H agglutinins for diagnosis of typhoid fever caused by Salmonella Typhi, published by Universities Press.

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Biochemistry & Agriculture

The vaccine against polio viruses is an example of:

Polio vaccines both OPV and IPV stimulate host immune system to produce memory cells and neutralizing antibodies against poliovirus. This active immunization requires immune response generation, unlike passive immunization involving direct transfer of ready-made immunoglobulins temporarily.

Ref: Park, Park's Textbook of Preventive and Social Medicine, 26th Edition, Chapter 7 Immunization and Plotkin Vaccines, classifies polio vaccines IPV and OPV as active immunization inducing long-term memory and neutralizing antibodies, published by Elsevier Saunders.

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Biochemistry & Agriculture

The infectious stage of Plasmodium that enters the human body is:

Plasmodium sporozoites injected by Anopheles mosquito during blood meal migrate to liver hepatocytes. This infective stage initiates pre-erythrocytic schizogony before merozoites enter erythrocytes, establishing clinical malaria infection cycle in humans efficiently.

Ref: Garcia, Tropical Parasitology and CDC Malariology Manual, Plasmodium Life Cycle chapter, and Paniker's Textbook of Medical Parasitology, defines sporozoites as infectious stage inoculated by Anopheles mosquito entering human liver, published by Jaypee Brothers.

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Biochemistry & Agriculture

Which type of immunity is developed after exposure to pathogens?

Natural active acquired immunity develops following natural infection where host immune system generates memory B and T cells against pathogen. This long-lasting protection contrasts with artificial immunity from vaccines or passive transfer of preformed antibodies externally.

Ref: Delves et al., Roitt's Essential Immunology, 13th Edition, Chapter 10 Acquired Immunity, distinguishes natural active acquired immunity developed after pathogen exposure with memory formation from artificial and passive types, published by Wiley-Blackwell.

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Biochemistry & Agriculture

Perforin lined pores in target cell are developed by:

Natural killer cells release perforin and granzymes from cytotoxic granules upon recognition of virus-infected or malignant targets. Perforin polymerizes forming transmembrane pores facilitating granzyme entry triggering caspase-dependent apoptosis, independent of MHC restriction for killing.

Ref: Abbas, Lichtman and Pillai, Cellular and Molecular Immunology, 10th Edition, Chapter 12 Immunity to Microbes and NK Cells, describes natural killer cells forming perforin-lined pores delivering granzymes inducing target apoptosis without MHC restriction, published by Elsevier.

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Biochemistry & Agriculture

Which of the following produce antibodies?

B lymphocytes differentiate into plasma cells upon antigen stimulation and T helper interaction, synthesizing and secreting immunoglobulins. These antibodies mediate humoral immunity through neutralization, opsonization, and complement activation, unlike T cells, monocytes, or granulocytes primarily.

Ref: Owen, Punt and Stranford, Kuby Immunology, 8th Edition, Chapter 2 Innate and Adaptive Immunity and Chapter 9 B Cell Activation, states B-lymphocytes differentiate into plasma cells producing antibodies mediating humoral immunity, published by W.H. Freeman.

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Biochemistry & Agriculture

Radioactive decay of the nucleus emits which of the following electromagnetic radiations?

Gamma rays are high-energy electromagnetic photons emitted from unstable nuclei during alpha or beta decay when daughter nucleus transitions from excited state. Their high penetration distinguishes them from UV, IR, and X-rays produced by extranuclear processes.

Ref: Krane, Introductory Nuclear Physics, Revised Edition, Chapter 9 Gamma Decay and Lilley, Nuclear Physics Principles, explains radioactive decay emits gamma rays as high-energy electromagnetic radiation from excited nuclei during de-excitation, published by Wiley.

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Biochemistry & Agriculture

The dual resistance vector is:

pBR322 is an early artificial E. coli cloning vector carrying ampicillin and tetracycline resistance genes as dual selectable markers. Its small size, high copy number, and unique restriction sites enabled insertional inactivation screening for recombinant selection.

Ref: Brown, Gene Cloning and DNA Analysis, 7th Edition, Chapter 6 Cloning Vectors and Primrose, Principles of Gene Manipulation, describes pBR322 as dual antibiotic resistance vector carrying ampicillin and tetracycline markers for selection, published by Wiley-Blackwell.

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Biochemistry & Agriculture

The computational methodology that tries to find the best matching between two molecules, a receptor and ligand is calle

Molecular docking predicts preferred orientation and binding affinity of ligand within receptor active site using scoring functions and conformational search algorithms. It underpins structure-based drug design for lead optimization and virtual screening of compound libraries.

Ref: Leach, Molecular Modelling Principles and Applications, 2nd Edition, Chapter 8 Docking and Drug Design, defines molecular docking as computational methodology predicting optimal receptor-ligand binding poses and affinities using scoring functions, published by Pearson Education.

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Biochemistry & Agriculture

The first clinical application of gene therapy over a 4-year-old girl was for:

The first FDA-approved gene therapy trial in 1990 treated Ashanti DeSilva aged four with adenosine deaminase deficiency causing SCID. Autologous T cells transduced with functional ADA cDNA via retroviral vector restored immune function temporarily, pioneering therapy.

Ref: Friedmann and Roblin, Gene Therapy, Science 1972 proposal and Watson et al., Molecular Biology of the Gene, 7th Edition, Chapter 19 Human Genetics, documents first clinical gene therapy trial in 1990 for adenosine deaminase deficiency SCID, published by Pearson.

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Biochemistry & Agriculture

Which of the following amino acids does not have an aromatic ring?

Proline contains pyrrolidine ring attached to alpha carbon, not an aromatic benzene-type system. Tryptophan possesses indole, tyrosine phenol, and histidine imidazole, all meeting aromaticity criteria with conjugated pi electrons, while proline is imino acid.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 3 Amino Acids and Proteins, classifies tryptophan, tyrosine, histidine as aromatic amino acids with conjugated rings while proline is imino acid with pyrrolidine ring, published by W.H. Freeman.

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Biochemistry & Agriculture

The colour of earthworm body is brown due to:

Earthworm dorsal body wall contains porphyrin pigment deposited in cuticle and epidermis, imparting brown color. Unlike hemoglobin in blood, porphyrin acts as photoprotective substance shielding tissues from UV radiation, contributing to body coloration and light sensitivity.

Ref: Barnes, Invertebrate Zoology, 5th Edition and Kotpal, Modern Textbook of Zoology Invertebrates, Chapter Annelida Earthworm, states brown coloration of body wall is due to porphyrin pigment deposition providing photoprotection, not hemoglobin, published by Saunders.

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