Paper I — Q3
Describe the uterus under the following headings: (i) Gross anatomy (ii) Ligaments and supports (iii) Relations of uterus (iv)…
Describe the uterus under the following headings: Gross anatomy
Ligaments and supports
Relations of uterus
Blood supply
Lymphatic drainage
Applied aspects
Which antibiotics and toxins inhibit protein synthesis in prokaryotes and eukaryotes? Briefly explain the mechanism of action of each of them.
What are ribozymes? Explain briefly the role of any one ribozyme in protein synthesis.
Enumerate the major hormonal causes of dwarfism. Give their characteristic features.
Describe the principal events during oogenesis in brief.
हिंदी में प्रश्न पढ़ें
गर्भाशय का वर्णन निम्नलिखित शीर्षकों के अंतर्गत कीजिए : सकल शारीर
स्नायु एवं अवलम्ब
गर्भाशय के संबंध
रक्त आपूर्ति
लसीका जल-निकासी
अनुप्रयुक्त पहलू
कौन-से एंटीबायोटिक तथा कौन-से टॉक्सिन प्राकृतिककों और युक्रियकों में प्रोटीन संश्लेषण का संदमन करते हैं? प्रत्येक के कार्य करने की क्रियाविधि संक्षेप में समझाइए।
राइबोजाइम क्या होते हैं? प्रोटीन संश्लेषण में किसी एक राइबोजाइम की भूमिका संक्षेप में समझाइए।
बामना के प्रमुख हार्मोनल कारण गिनाइए। उनकी लाक्षणिक विशिष्टताएं बताइए।
डिंबजनन में होने वाली प्रमुख घटनाओं का संक्षेप में वर्णन कीजिए।
Model answer
Drafted with AI by UPSC Answer Check against this question's marking rubric, to the expected length. UPSC does not publish answers for Mains — this is one way to score well, not an official key. How we build rubrics and answers.
(a) Uterus. The uterus is a pear-shaped, thick-walled muscular organ, about 7.5 × 5 × 2.5 cm and 50–70 g, with fundus, body, isthmus and cervix, normally anteverted and anteflexed. Its wall has perimetrium, thick myometrium and endometrium (basal and functional layers). The broad ligament (mesometrium, mesosalpinx, mesovarium), round ligament (covered by peritoneum), uterosacral, pubocervical and cardinal/transverse cervical ligaments of Mackenrodt, with levator ani and urogenital diaphragm, support it. Anteriorly it lies with bladder and vesicouterine pouch; posteriorly with rectum and rectouterine pouch of Douglas; laterally with broad ligament, uterine artery and ureter. Blood supply is from uterine artery (anterior division of internal iliac) and ovarian artery (aorta); arcuate arteries in myometrium give radial arteries, which give basal and spiral arterioles; veins drain via uterine and ovarian plexuses, chiefly to internal iliac veins. Lymph from fundus/upper body goes to para-aortic nodes along ovarian vessels, and from near the cornua to superficial inguinal nodes along the round ligament; lower body/cervix to external/internal iliac, and cervix also to obturator/sacral nodes. Applied aspects include retroversion, prolapse with cystocele/rectocele, hysterectomy with ureter injury, endometrial carcinoma staging and leiomyoma.
(b)(i) Protein synthesis inhibitors. In prokaryotes, tetracyclines block the A-site on 30S; chloramphenicol inhibits 50S peptidyl transferase; macrolides block translocation on 50S; aminoglycosides cause 30S misreading; linezolid inhibits 70S initiation. Prokaryotic toxins include bacteriocins such as colicin E3, which cleaves 16S rRNA at the decoding site. In eukaryotes, cycloheximide blocks 60S translocation; puromycin mimics aminoacyl-tRNA and causes premature termination; diphtheria toxin ADP-ribosylates eEF-2; ricin depurinates 28S rRNA.
(b)(ii) Ribozymes. Ribozymes are catalytic RNAs; examples include RNase P and self-splicing introns. In protein synthesis, the peptidyl-transferase centre of 23S rRNA (bacteria) or 28S rRNA (eukaryotes) catalyses peptide-bond formation between peptidyl-tRNA and aminoacyl-tRNA.
(c)(i) Hormonal dwarfism. GH deficiency causes proportionate short stature with delayed bone age. Hypothyroidism/cretinism causes disproportionate short stature, coarse facies, hypotonia and intellectual disability. Glucocorticoid excess causes growth failure with obesity, hypertension and striae. Hypopituitarism/panhypopituitarism causes multiple hormone deficiencies; Laron GH resistance (high GH, low IGF-1) causes short stature. Precocious puberty causes early sexual maturation and early epiphyseal closure, limiting adult height.
(c)(ii) Oogenesis. Fetal oogonia proliferate mitotically and enter meiosis I, arresting in dictyate/prophase I. From puberty, one primary oocyte completes meiosis I to form secondary oocyte and first polar body; it arrests in metaphase II, ovulates, and completes meiosis II only if fertilized, forming the second polar body.
How this answer will be evaluated
Framework: null
What earns full marks: Comprehensive, accurate, and well-structured answers with all required details and mechanisms.
Evaluation rubric
Each sub-part is marked on its own, against the marks and word limit printed on the paper.
- (a) Uterus: gross anatomy, ligaments and supports, relations, blood supply, lymphatic drainage, applied aspects. 20 marks
describe— define → structure or process in order → labelled diagram → significance
Must cover
- Parts (fundus, body, isthmus, cervix), size, anteverted–anteflexed position, layers
- Supports: pelvic floor (levator ani), cardinal (Mackenrodt), uterosacral, pubocervical ligaments; broad and round ligaments as secondary
- Relations: bladder/vesicouterine pouch, rectum/pouch of Douglas, broad ligament, uterine artery crossing ureter
- Blood (uterine and ovarian arteries; arcuate, radial, spiral) and lymph (para-aortic, superficial inguinal via round ligament, iliac, sacral); applied — prolapse, ureter injury in hysterectomy, fibroids, carcinoma spread
Loses marks
- Treating broad ligament as main support
Earns more
- Labelled diagram
Extra mark
- Developmental anomalies
- (b)(i) Antibiotics and toxins inhibiting protein synthesis in prokaryotes and eukaryotes with mechanisms. 10 marks
explain— definition/context → points in order → small example → short close
Must cover
- 30S inhibitors: aminoglycosides (misreading), tetracyclines (block aminoacyl-tRNA binding)
- 50S inhibitors: chloramphenicol (peptidyl transferase), macrolides (translocation), linezolid (initiation complex)
- Eukaryotic: cycloheximide (60S translocation), diphtheria toxin (ADP-ribosylates eEF-2), ricin/shiga toxin (28S rRNA depurination)
- Puromycin in both (premature chain termination)
Loses marks
- Wrong subunit targets
Earns more
- Streptomycin at initiation
Extra mark
- Clinical relevance (grey baby syndrome)
- (b)(ii) Ribozymes; role of one ribozyme in protein synthesis. 5 marks
explain— definition/context → points in order → small example → short close
Must cover
- Definition: catalytic RNA
- Examples: RNase P, self-splicing introns, spliceosomal snRNA, peptidyl transferase
- 23S (prokaryotes)/28S (eukaryotes) rRNA as peptidyl transferase forming peptide bonds
- Brief mechanism in the ribosomal large subunit
Loses marks
- Calling ribozyme a protein enzyme
Earns more
- Discovery (Cech, Altman)
Extra mark
- RNA-world significance
- (c)(i) Major hormonal causes of dwarfism with characteristic features. 10 marks
enumerate— list the items in order → one line each → no commentary
Must cover
- GH deficiency: proportionate, normal intelligence, delayed bone age, cherubic face
- Hypothyroidism (cretinism): disproportionate, mental retardation, coarse features
- Glucocorticoid excess, Laron syndrome (GH resistance, low IGF-1)
- Precocious puberty/sex-steroid excess: early epiphyseal fusion; others (diabetes, pseudohypoparathyroidism)
Loses marks
- Achondroplasia as hormonal
Earns more
- Investigations
Extra mark
- Treatment principles
- (c)(ii) Principal events during oogenesis. 5 marks
describe— define → structure or process in order → labelled diagram → significance
Must cover
- Oogonia multiply in fetal ovary; primary oocytes enter meiosis I and arrest in prophase I (diplotene)
- At puberty, cyclic completion of meiosis I before ovulation → secondary oocyte + first polar body
- Arrest in metaphase II; completion only on fertilisation → second polar body
- Follicular development stages
Loses marks
- Meiosis II completed before ovulation
Earns more
- Numbers of oocytes over life
Extra mark
- Comparison with spermatogenesis
What "Describe" is asking you to do
Give a full, ordered account of the thing named — its parts, stages or mechanism — in the sequence in which it actually exists or occurs. Most describe questions come from the science optionals, where the marks sit in correct technical detail and, where the stem says so, a labelled diagram.
Structure that answers it
One-line identification of the subject → the parts or stages in their real order, each with its defining detail → labelled diagram where the subject is structural → closing line on function or significance
Where marks are lost
Loose general prose where the examiner is ticking named parts, correct terminology and their sequence; and in the General Studies papers, turning to evaluation before the description is finished.
Practice this exact question
Write your answer and it is marked point by point against the model answer above — what you covered, what you missed, what you got wrong.
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