DHR - BRET Biochemistry PYQs Sept 2024

Plant Physiology & Molecular Techniques

The trisomy condition in Down Syndrome is due to non-disjunction of chromosome during gamete formation. This process occ

Down syndrome 47, +21 typically arises from meiotic nondisjunction in maternal meiosis I during gametogenesis producing disomic oocyte, fertilized to trisomic zygote, not from mitotic errors in somatic cells of parents.

Ref: Robert L. Nussbaum, Roderick R. McInnes and Huntington F. Willard, Thompson & Thompson Genetics in Medicine, 8th Edition, Chapter 6 Chromosomal Disorders, section on Down Syndrome Trisomy 21 Due to Meiotic Nondisjunction During Gamete Formation, Elsevier Saunders.

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Plant Physiology & Molecular Techniques

Klinefelter syndrome is

Klinefelter 47,XXY results from nondisjunction of sex chromosomes leading to sex chromosome aneuploidy with tall stature, gynecomastia, small testes, hypergonadotropic hypogonadism and infertility, distinct from autosomal trisomy 21 causing Down syndrome and its phenotype.

Ref: Robert L. Nussbaum, Roderick R. McInnes and Huntington F. Willard, Thompson & Thompson Genetics in Medicine, 8th Edition, Chapter 6 Chromosomal Disorders, section on Sex Chromosome Aneuploidies and Klinefelter Syndrome 47,XXY Genetics, Elsevier Saunders.

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Plant Physiology & Molecular Techniques

Telomerase enzyme plays role in

Telomerase is ribonucleoprotein reverse transcriptase carrying RNA template that adds TTAGGG telomeric repeats to eukaryotic chromosome 3' ends, compensating for end-replication problem in lagging strand synthesis, preventing senescence, not involved in whole genome replication.

Ref: Bruce Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 5 DNA Replication and Chapter 8 Telomeres and Telomerase Mechanism for Chromosome End Extension Solving End-Replication Problem, Garland Science.

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Plant Physiology & Molecular Techniques

Genetic code refers to the

Genetic code defines relationship between 64 triplet codons in mRNA and 20 amino acids, being degenerate, universal and non-overlapping, encoding specific amino acids or stop signals during translation at ribosome.

Ref: James D. Watson, Tania A. Baker, Stephen P. Bell and Alexander Gann, Molecular Biology of the Gene, 7th Edition, Chapter 9 Genetic Code, section on Triplet Codon to Amino Acid Correspondence and its Properties, Pearson Education.

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Plant Physiology & Molecular Techniques

A 36-year-old woman reported muscle weakness in the extraocular eye muscles and muscles of the extremities. Her muscle w

Autoantibodies against nicotinic acetylcholine receptors at neuromuscular junction cause fatigable weakness of ocular and limb muscles worsening with activity and improving with rest, sparing sensation, distinguishing myasthenia gravis from muscular dystrophy or neuropathies.

Ref: J. Larry Jameson et al., Harrison's Principles of Internal Medicine, 20th Edition, Chapter 440 Myasthenia Gravis and Disorders of Neuromuscular Junction, pathophysiology of Anti-AChR Antibodies and Fatigable Weakness, McGraw-Hill Education.

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Plant Physiology & Molecular Techniques

Given below are two statements : Statement I : Conditioned reflex is a classic example of dissociative learning . Statem

Conditioned reflex exemplifies associative learning, not dissociative, where a neutral conditioned stimulus after repeated pairing with unconditioned stimulus that normally elicits response begins to elicit similar response alone, as described by Pavlov.

Ref: Eric R. Kandel, James H. Schwartz and Thomas M. Jessell, Principles of Neural Science, 5th Edition, Chapter 53 Learning and Memory, section on Classical Conditioning and Associative Learning versus Dissociative Learning Definitions, McGraw-Hill.

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Plant Physiology & Molecular Techniques

Which of the following statements are CORRECT regarding angiotensin II? (A) It increases the glomerular filtration rate

Angiotensin II directly enhances Na+ and water reabsorption in proximal tubule, stimulates zona glomerulosa to release aldosterone, and is generated from angiotensin I by angiotensin converting enzyme in lungs, thereby supporting extracellular fluid volume and blood pressure regulation.

Ref: John E. Hall and Arthur C. Guyton, Guyton and Hall Textbook of Medical Physiology, 14th Edition, Chapter 27 Renin Angiotensin Aldosterone System, section on Angiotensin II Actions on Sodium Reabsorption, Aldosterone Secretion and ACE Conversion, Elsevier.

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Plant Physiology & Molecular Techniques

Which of the following factors lead to an increased cardiac output? (A) Increased sympathetic stimulation (B) Increased

Sympathetic activation and circulating catecholamines increase heart rate and contractility via beta-1 adrenergic receptors, enhancing stroke volume and cardiac output, while hypothermia and calcium channel blockers depress contractility and reduce output.

Ref: John E. Hall and Arthur C. Guyton, Guyton and Hall Textbook of Medical Physiology, 14th Edition, Chapter 20 Cardiac Muscle and Chapter 24 Cardiac Output Regulation by Sympathetic System and Catecholamines and Contractility, Elsevier.

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Plant Physiology & Molecular Techniques

Which of the following statements are correct regarding the term ‘Steatorrhea’? (A) It is passage of fatty, bulky and cl

Steatorrhea denotes bulky, fatty, pale clay-colored stools from fat maldigestion and malabsorption due to exocrine pancreatic destruction, lipase deficiency, bile salt deficiency or mucosal disease, leading to increased fecal fat excretion.

Ref: J. Larry Jameson et al., Harrison's Principles of Internal Medicine, 20th Edition, Chapter 324 Approach to Malabsorption and Steatorrhea, discussion on Pancreatic Exocrine Insufficiency, Lipase Deficiency and Fat Malabsorption, McGraw-Hill Education.

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Plant Physiology & Molecular Techniques

Which of the following statements are correct? (A) Oxygen and carbon dioxide diffuse into and out of capillaries followi

O2 and CO2 diffuse down partial pressure gradients, hemoglobin massively increases O2 carrying capacity and also transports CO2 as carbaminohemoglobin, majority CO2 travels as bicarbonate not carbolic acid, while buffers stabilize blood pH.

Ref: John E. Hall and Arthur C. Guyton, Guyton and Hall Textbook of Medical Physiology, 14th Edition, Chapter 40 Gas Transport in Blood, topic on Oxygen Hemoglobin Binding, CO2 Transport as Bicarbonate and Buffer Systems, Elsevier.

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Plant Physiology & Molecular Techniques

Given below are two statements: Statement I : Respiratory acidosis is caused by an abnormally high PCO₂ in systemic arte

Respiratory acidosis arises when arterial PCO2 exceeds 45 mmHg due to hypoventilation or diffusion defect, causing CO2 retention, rising carbonic acid formation and H+ accumulation, thus both statements correctly describe cause and mechanistic consequence.

Ref: John E. Hall and Arthur C. Guyton, Guyton and Hall Textbook of Medical Physiology, 14th Edition, Chapter 31 Acid-Base Regulation, section on Respiratory Acidosis Pathophysiology with Elevated PCO2 and H2CO3 Formation, Elsevier Saunders.

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Plant Physiology & Molecular Techniques

Which of the following statements are correct regarding the “surfactant” lining the alveoli of lungs? (A) It helps in pr

Pulmonary surfactant secreted by type II pneumocytes reduces surface tension via dipalmitoyl phosphatidylcholine preventing alveolar collapse at expiration. Its deficiency, not excess, causes infant respiratory distress syndrome due to atelectasis and impaired compliance.

Ref: John E. Hall and Arthur C. Guyton, Guyton and Hall Textbook of Medical Physiology, 14th Edition, Chapter 39 Pulmonary Surfactant and Chapter 44 Respiratory Distress Syndrome, role of Type II Cells and DPPC preventing alveolar collapse, Elsevier.

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