Medical Science 2023 Paper I 50 marks Describe

Q4

(a) (i) Describe the role of SRY (Sex-determining region on Y gene) transcription factors in testicular development. 10 (ii) Describe Vitelline duct abnormalities. 5 (b) (i) Describe the role of iodine in the synthesis of thyroid hormones. Discuss briefly about Hashimoto's Thyroiditis and the biochemical investigations that will be done for its diagnosis. 15 (ii) Explain briefly the biochemical role of Vitamin-K in the body. What is the biochemical basis of using Warfarin as an anticoagulant drug ? 5 (c) (i) Describe the functions of vasopressin and the regulation of vasopressin secretion. 5+5=10 (ii) Describe the physiological effects of glucagon. 5

हिंदी में प्रश्न पढ़ें

(a) (i) वृषण के विकास में वाई जीन के लिंग-निर्धारक क्षेत्र (SRY) के अनुलेखन घटकों की भूमिका का वर्णन कीजिए । (ii) पीतक कोश वाहिनी की अपसामान्यताओं का वर्णन कीजिए । (b) (i) अवटु हार्मोनों के संश्लेषण में आयोडीन की भूमिका का वर्णन कीजिए । हैशिमोटो अवटुशोथ और उसके निदान के लिए की जाने वाली जैव-रासायनिक जाँचों की संक्षेप में व्याख्या कीजिए । (ii) शरीर में विटामिन-के की जैव-रासायनिक भूमिका की संक्षिप्त व्याख्या कीजिए । वारफेरिन के स्कन्दनरोधी औषध के रूप में प्रयुक्त किए जाने के पीछे क्या जैव-रासायनिक आधार है ? (c) (i) वैसोप्रेसिन के कार्यों तथा वैसोप्रेसिन स्रवण नियमन का वर्णन कीजिए । (ii) ग्लूकागॉन के शारीरिकीयात्मक प्रभावों का वर्णन कीजिए ।

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Directive word: Describe

This question asks you to describe. The directive word signals the depth of analysis expected, the structure of your answer, and the weight of evidence you must bring.

See our UPSC directive words guide for a full breakdown of how to respond to each command word.

How this answer will be evaluated

Approach

The directive 'describe' demands comprehensive, structured exposition of mechanisms and features across all sub-parts. Allocate approximately 35% of time/words to (b)(i) as it carries 15 marks; 20% each to (a)(i) and (c)(i) at 10 marks each; and 15% combined for the three 5-mark sub-parts (a)(ii), (b)(ii), (c)(ii). Structure as: embryology section → endocrinology section → biochemistry section, with brief introductions and summaries for each major part.

Key points expected

SRY gene mechanism: SOX9 upregulation, SF1 interaction, testis-specific enhancer (TSE), Sertoli cell differentiation and AMH secretion
Vitelline duct abnormalities: Meckel's diverticulum (Rule of 2s), vitelline fistula, umbilical sinus, vitelline cyst; embryological basis of persistence
Iodine in thyroid hormone synthesis: iodide trapping by NIS, organification by TPO, coupling reaction; Hashimoto's as autoimmune destruction with anti-TPO and anti-Tg antibodies, elevated TSH, low T3/T4
Vitamin K biochemistry: gamma-carboxylation of glutamate residues (GLA domain) in Factors II, VII, IX, X; Warfarin as vitamin K epoxide reductase (VKORC1) inhibitor creating functional deficiency
Vasopressin (ADH): V2 receptor-mediated water reabsorption in collecting ducts via aquaporin-2 insertion; osmoreceptor (hypothalamic) and volume/pressure (baroreceptor) regulation; SIADH and diabetes insipidus correlation
Glucagon effects: glycogenolysis, gluconeogenesis, lipolysis, ketogenesis; cAMP/PKA signaling pathway; counter-regulatory hormone role

Evaluation rubric

Dimension	Weight	Max marks	Excellent	Average	Poor
Concept correctness	25%	12.5	Precise molecular mechanisms: for (a)(i) details SRY-SOX9-SF1 cascade and testis cord formation; for (b)(i) correctly sequences iodide transport, oxidation, coupling; for (b)(ii) accurately describes VKORC1 inhibition by warfarin; no factual errors in hormone signaling pathways	Broadly correct but misses key molecular details (e.g., mentions SRY causes testis development without SOX9 mechanism; describes iodine 'needed' for thyroid hormones without organification steps; vague on warfarin mechanism)	Major conceptual errors (e.g., confuses SRY with androgen receptor; states iodine deficiency causes Hashimoto's; describes warfarin as thrombin inhibitor directly; confuses glucagon with insulin actions)
Clinical correlation	20%	10	Strong disease links: for (a)(ii) connects Meckel's to intestinal obstruction/bleeding; for (b)(i) correlates Hashimoto's with goiter, hypothyroidism, and Indian iodine supplementation program relevance; for (c)(i) links vasopressin to SIADH/diabetes insipidus; for (c)(ii) connects glucagon to diabetic ketoacidosis and glucagonoma	Mentions clinical conditions superficially (e.g., lists Hashimoto's as 'thyroiditis' without hypothyroidism features; notes diabetes insipidus without central vs nephrogenic distinction; minimal Indian public health context)	Absent or incorrect clinical correlations (e.g., no mention of complications; confuses Hashimoto's with Graves' disease; describes vasopressin only as 'stress hormone' without endocrine pathology)
Diagram / pathway	20%	10	Includes well-labeled diagrams: for (a)(i) SRY gene structure and downstream targets; for (b)(i) thyroid hormone synthesis pathway with follicular cell schematic; for (b)(ii) vitamin K cycle showing epoxide reductase inhibition; for (c)(i) hypothalamic-posterior pituitary axis; clear hand-drawn quality with arrows and labels	Attempts diagrams but incomplete or poorly labeled (e.g., thyroid follicle without iodide transport details; vitamin K cycle missing reductase step; vasopressin pathway without neurohypophysis connection); text descriptions substitute for visual elements	No diagrams despite pathway-heavy content; or diagrams with fundamental errors (e.g., anterior pituitary shown for vasopressin; incorrect feedback loops; mislabeled structures)
Differential / staging	15%	7.5	Clear differentiation: for (a)(ii) distinguishes Meckel's from other vitelline remnants (fistula, cyst, sinus) by anatomical features; for (b)(i) stages Hashimoto's progression (euthyroid → subclinical → overt hypothyroidism) with antibody patterns; for (c)(i) differentiates central vs nephrogenic diabetes insipidus; for (c)(ii) contrasts glucagon actions by tissue	Lists types without clear distinguishing features (e.g., mentions 'different types of vitelline abnormalities' without anatomical basis; notes Hashimoto's 'stages' without TSH/T4 correlation; minimal differential approach)	No differential or staging attempted; or conflates distinct entities (e.g., treats all vitelline abnormalities as 'Meckel's diverticulum'; no progression concept in autoimmune thyroiditis; confuses glucagon and cortisol actions)
Management / public-health angle	20%	10	Integrates relevant management: for (b)(i) mentions levothyroxine replacement and monitoring; for (b)(ii) discusses warfarin dosing, INR monitoring, vitamin K reversal; for (c)(i) notes desmopressin therapy; references Indian iodine deficiency disorders (IDD) control program, salt iodization; mentions glucagon as emergency hypoglycemia treatment	Brief mention of treatments without specifics (e.g., 'thyroid hormone replacement' without naming levothyroxine; 'anticoagulant monitoring' without INR; generic 'hormone therapy' for diabetes insipidus); minimal public health reference	No management or public health content; or dangerously incorrect (e.g., suggests iodine treatment for Hashimoto's; describes stopping warfarin without reversal agent; no recognition of India's IDD program relevance)

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