Mock Exam 12
Mock Exam 12 — MRCOG Part 1 SBAs
Embryology · Genetics · Pathology
100 Questions — Answers & Explanations
Embryology
📘 Q1 (Embryology) — During oogenesis, the stage at which meiosis resumes just prior to ovulation is: A) Dictyate stage B) Metaphase II C) Anaphase I D) Prophase I E) Telophase II
Answer: B
Oocytes are arrested at prophase I (dictyate stage) from fetal life until puberty. In response to the LH surge, the primary oocyte completes meiosis I and progresses to metaphase II, where it arrests again. Ovulation releases a secondary oocyte at metaphase II; meiosis II is completed only if fertilisation occurs.
📘 Q2 (Embryology) — The acrosome reaction of spermatozoa occurs primarily to: A) Activate the fertilised ovum B) Enable the sperm to penetrate the zona pellucida C) Fuse with the vitelline membrane of the oocyte D) Trigger the cortical reaction E) Neutralise the acid pH of the female genital tract
Answer: B
The acrosome reaction involves exocytosis of hydrolytic enzymes (e.g., acrosin, hyaluronidase) from the sperm head, which digest the zona pellucida. This allows the sperm to reach the oolemma and fuse with the oocyte. The cortical reaction is triggered by sperm–oocyte fusion, not by the acrosome reaction itself.
📘 Q3 (Embryology) — The zona pellucida is composed primarily of: A) Hyaluronic acid B) Zona proteins (ZP1, ZP2, ZP3) C) Mucopolysaccharides D) Laminin and fibronectin E) Acidic glycoproteins secreted by the cumulus oophorus
Answer: B
The zona pellucida is an extracellular glycoprotein coat composed of three major proteins: ZP1, ZP2, and ZP3. ZP3 serves as the primary sperm receptor and is critical for species-specific sperm binding and induction of the acrosome reaction. It is secreted by the growing oocyte, not the cumulus cells.
📘 Q4 (Embryology) — Implantation of the blastocyst into the endometrium normally occurs on which day after fertilisation? A) Day 3 B) Day 5 C) Day 6–7 D) Day 10–12 E) Day 14
Answer: C
The blastocyst hatches from the zona pellucida around day 5–6 and begins implantation approximately on day 6–7 after fertilisation. The process involves apposition, adhesion, and invasion of the trophoblast into the decidualised endometrium. Implantation is largely complete by day 12.
📘 Q5 (Embryology) — The decidual reaction of the endometrium is primarily induced by: A) Oestrogen from the developing follicle B) Human chorionic gonadotrophin (hCG) from the syncytiotrophoblast C) Progesterone from the corpus luteum D) Prostaglandins from the endometrium E) Human placental lactogen (hPL)
Answer: C
Decidualisation involves transformation of endometrial stromal cells into specialised decidual cells that provide a nutritive and immunologically privileged environment. Progesterone from the corpus luteum is the principal hormonal driver; oestrogen primes the endometrium but progesterone induces the secretory transformation and decidualisation.
📘 Q6 (Embryology) — Which of the following is derived from the syncytiotrophoblast? A) Amniotic membrane B) Chorionic villi cytotrophoblast C) Human chorionic gonadotrophin (hCG) D) Yolk sac endoderm E) Extraembryonic mesoderm
Answer: C
The syncytiotrophoblast is a multinucleated, invasive layer derived from fusion of cytotrophoblast cells. It is the principal endocrine tissue of the early placenta, secreting hCG, hPL, and progesterone. hCG is detectable in maternal serum from around the time of implantation and forms the basis of pregnancy tests.
📘 Q7 (Embryology) — The umbilical cord normally contains: A) Two arteries and one vein B) One artery and two veins C) Two arteries and two veins D) One artery and one vein E) Three arteries and one vein
Answer: A
The normal umbilical cord contains two umbilical arteries (carrying deoxygenated blood from fetus to placenta) and one umbilical vein (carrying oxygenated blood from placenta to fetus). A single umbilical artery (SUA) is associated with fetal anomalies and aneuploidy, particularly trisomy 18.
📘 Q8 (Embryology) — The notochord is derived from which germ layer and is critical for: A) Mesoderm — forming the vertebrae B) Ectoderm — patterning the spinal cord C) Mesoderm — inducing neural tube formation D) Endoderm — forming the gut tube E) Ectoderm — forming the somites
Answer: C
The notochord is a midline mesodermal structure that forms during gastrulation. It serves as the primary inducer of the overlying ectoderm to differentiate into the neural plate (neurulation). The notochord also patterns the paraxial mesoderm into somites and ultimately degenerates into the nucleus pulposus of intervertebral discs.
📘 Q9 (Embryology) — Failure of the neural tube to close at the cranial end results in: A) Spina bifida occulta B) Meningocele C) Anencephaly D) Myelomeningocele E) Encephalocele
Answer: C
Neural tube closure begins in the cervical region and proceeds both cranially and caudally. Failure of the anterior neuropore to close by day 25–26 results in anencephaly, a lethal condition characterised by absence of the forebrain and calvarium. Folic acid supplementation before conception and in early pregnancy significantly reduces the risk of neural tube defects.
📘 Q10 (Embryology) — The urogenital sinus is an endodermal structure that gives rise to: A) The kidneys and ureters B) The urinary bladder, urethra, and lower vaginal tract C) The ovaries and testes D) The fallopian tubes and uterus E) The adrenal cortex
Answer: B
The urogenital sinus is derived from the cloaca (endoderm) after division by the urorectal septum. In females, it forms the urinary bladder, urethra, vestibular glands (Bartholin's), and the lower third of the vagina (the upper two-thirds derive from the paramesonephric ducts).
📘 Q11 (Embryology) — The paramesonephric (Müllerian) ducts develop into which female structures? A) Ovaries and fallopian tubes B) Fallopian tubes, uterus, cervix, and upper vagina C) Ovaries and uterus only D) Uterus, cervix, and lower vagina E) Ovaries, fallopian tubes, and uterus
Answer: B
The paramesonephric ducts arise laterally to the mesonephric (Wolffian) ducts. In the absence of anti-Müllerian hormone (AMH), they develop into the fallopian tubes (cranial unfused portion), uterus and cervix (fused caudal portion), and the upper two-thirds of the vagina. The ovaries develop from the genital ridges (mesoderm), not the paramesonephric ducts.
📘 Q12 (Embryology) — The mesonephric (Wolffian) ducts in female embryos: A) Form the fallopian tubes B) Regress due to absence of testosterone C) Form the rete ovarii D) Persist as the Gartner's duct remnants E) Both B and D
Answer: E
In female embryos, the absence of testicular testosterone and AMH means the mesonephric ducts regress. Small remnants may persist as Gartner's duct cysts along the lateral wall of the vagina or cervix. The mesonephric ducts are the precursors of the epididymis, vas deferens, and seminal vesicles in males.
📘 Q13 (Embryology) — The most common congenital uterine anomaly associated with recurrent first-trimester miscarriage is: A) Septate uterus B) Bicornuate uterus C) Unicornuate uterus D) Didelphys uterus E) Arcuate uterus
Answer: A
A septate uterus results from incomplete resorption of the midline septum after fusion of the paramesonephric ducts. It carries the highest risk of recurrent miscarriage among Müllerian anomalies because the septum is poorly vascularised and cannot adequately support implantation and placentation. Hysteroscopic septum resection improves pregnancy outcomes.
📘 Q14 (Embryology) — The yolk sac is most clinically significant in pregnancy because: A) It produces hCG in early pregnancy B) It is the site of early haematopoiesis and is seen on ultrasound as a marker of an intrauterine pregnancy C) It forms the definitive placenta D) It gives rise to the amniotic cavity E) It secretes progesterone
Answer: B
The secondary yolk sac is the first extraembryonic structure visible on transvaginal ultrasound (around 5–6 weeks gestation). It serves as the site of primitive haematopoiesis (before the liver takes over) and supplies nutrients to the embryo before the uteroplacental circulation is established. An absent or abnormally large yolk sac is associated with poor pregnancy outcomes.
📘 Q15 (Embryology) — The transformation of the cytotrophoblast into the syncytiotrophoblast is mediated by: A) Hypoxia-inducible factor 1 alpha (HIF-1α) B) Human chorionic gonadotrophin (hCG) C) Fusion of cytotrophoblast cells involving syncytin-1 and syncytin-2 D) Apoptosis of cytotrophoblast cells E) Progesterone from the corpus luteum
Answer: C
Syncytins are envelope proteins of endogenous retroviral origin that mediate cell–cell fusion of cytotrophoblasts to form the syncytiotrophoblast layer. This fusion is essential for placental barrier formation and endocrine function. hCG is secreted by the syncytiotrophoblast but does not cause the fusion itself.
📘 Q16 (Embryology) — The trophoblast cells that invade the spiral arteries and remodel them into high-capacitance, low-resistance vessels are: A) Syncytiotrophoblast B) Villous cytotrophoblast C) Extravillous trophoblast D) Amnioblasts E) Decidual natural killer cells
Answer: C
Extravillous trophoblasts (EVTs) invade the decidua and myometrium and remodel the maternal spiral arteries by replacing the endothelial lining and destroying the muscular media. This creates low-resistance, high-flow vessels that ensure adequate blood supply to the intervillous space. Inadequate remodelling is implicated in pre-eclampsia and fetal growth restriction.
📘 Q17 (Embryology) — The diaphragm develops from which four embryonic structures? A) Septum transversum, pleuroperitoneal membranes, dorsal mesentery of oesophagus, and body wall B) Septum transversum, pericardial cavity, somites, and neural crest C) Pleuropericardial folds, septum transversum, laryngotracheal groove, and body wall D) Septum transversum, urogenital ridge, pleuroperitoneal membranes, and notochord E) Pericardial cavity, pleuroperitoneal membranes, dorsal mesentery, and amniotic folds
Answer: A
The diaphragm develops from four components: the septum transversum (central tendon), the paired pleuroperitoneal membranes (posterolateral portions), the dorsal mesentery of the oesophagus (crura), and the body wall (peripheral rim). Congenital diaphragmatic hernia most commonly occurs through a posterolateral defect (Bochdalek hernia) due to failure of pleuroperitoneal membrane fusion.
📘 Q18 (Embryology) — The pharyngeal arches develop into which branchial arch derivatives? The second pharyngeal arch forms the: A) Maxilla and mandible B) Stapes, styloid process, stylohyoid ligament, and part of the hyoid bone C) Greater horn of hyoid bone D) Thyroid and cricoid cartilages E) Thymus and parathyroid glands
Answer: B
Each pharyngeal arch has a nerve, artery, cartilage, and muscle component. The second (hyoid) arch cartilage (Reichert's) ossifies to form the stapes and styloid process and gives rise to the stylohyoid ligament and the lesser horn/upper body of the hyoid bone. The first arch forms Meckel's cartilage (malleus, incus, mandible).
📘 Q19 (Embryology) — Sirenomelia (mermaid syndrome) is associated with: A) Defective neural crest migration B) Abnormal development of the caudal mesoderm leading to fusion of the lower limbs C) Failure of the pharyngeal arches to develop D) Incomplete closure of the anterior abdominal wall E) Twinning defect with incomplete separation
Answer: B
Sirenomelia is a rare congenital anomaly characterised by fusion of the lower limbs, often with associated renal agenesis, absence of the bladder, and imperforate anus. It results from a vascular steal phenomenon involving the caudal mesoderm during early embryogenesis, leading to deficient development of the caudal structures.
📘 Q20 (Embryology) — The primitive heart tube forms from which of the following? A) Lateral plate mesoderm B) Paraxial mesoderm C) Intermediate mesoderm D) Splanchnic mesoderm E) Ectoderm
Answer: D
The cardiogenic region is derived from splanchnic (visceral) lateral plate mesoderm. Cells migrate to form the paired endocardial tubes that fuse into a single primitive heart tube. The heart begins beating around day 22–23. Paraxial mesoderm forms somites; intermediate mesoderm forms the urogenital system.
📘 Q21 (Embryology) — The foramen ovale in the fetal heart: A) Connects the pulmonary artery to the aorta B) Shunts blood from the right atrium to the left atrium C) Shunts blood from the right ventricle to the left ventricle D) Connects the umbilical vein to the inferior vena cava E) Allows blood to bypass the lungs by shunting from the pulmonary trunk to the aorta
Answer: B
The foramen ovale is an opening in the interatrial septum that allows oxygenated blood from the placenta (returning via the umbilical vein and inferior vena cava) to pass directly from the right atrium to the left atrium, bypassing the fetal pulmonary circulation. It closes functionally at birth due to increased left atrial pressure. The ductus arteriosus shunts blood from the pulmonary trunk to the aorta.
📘 Q22 (Embryology) — The external genitalia of a female fetus develop under the influence of: A) Oestrogen from the maternal ovary B) Testosterone from the fetal ovary C) The absence of androgens D) Dihydrotestosterone (DHT) E) Anti-Müllerian hormone (AMH)
Answer: C
Female external genitalia development does not require ovarian hormones; it occurs by default in the absence of androgens. Under the influence of oestrogen (from both mother and fetus), the genital tubercle becomes the clitoris, the urogenital folds become the labia minora, and the labioscrotal swellings become the labia majora. In males, DHT drives external genital masculinisation.
📘 Q23 (Embryology) — The ligamentum teres of the liver in the adult is a remnant of the: A) Ductus venosus B) Umbilical vein C) Umbilical artery D) Ductus arteriosus E) Foramen ovale
Answer: B
The umbilical vein carries oxygenated blood from the placenta to the fetal liver. After birth, it involutes to form the ligamentum teres (round ligament) of the liver, which runs from the umbilicus to the portal vein. The ductus venosus becomes the ligamentum venosum, and the ductus arteriosus becomes the ligamentum arteriosum.
📘 Q24 (Embryology) — In a bicornuate uterus, the embryological defect is: A) Failure of Müllerian duct development on one side B) Failure of Müllerian duct fusion C) Failure of resorption of the midline septum D) Failure of canalisation of the vagina E) Hypoplasia of the uterovaginal primordium
Answer: B
A bicornuate uterus results from incomplete fusion of the paramesonephric (Müllerian) ducts at the level of the uterine fundus, leading to a heart-shaped uterine cavity with a single cervix. This differs from a septate uterus (failure of septum resorption after normal fusion) and a unicornuate uterus (failure of one duct to develop).
📘 Q25 (Embryology) — The cloaca is divided by the urorectal septum into: A) Urogenital sinus and anorectal canal B) Bladder and urethra C) Rectum and anal canal D) Vagina and rectum E) Allantois and hindgut
Answer: A
The cloaca is the terminal end of the hindgut that is divided by the urorectal septum (of Tourneux) into the urogenital sinus (anteriorly) and the anorectal canal (posteriorly). The division is completed by week 7. Failure of this separation results in a persistent cloaca, a rare congenital anomaly.
📘 Q26 (Embryology) — Which of the following congenital anomalies is associated with failure of the vitelline duct to obliterate? A) Tracheo-oesophageal fistula B) Meckel's diverticulum C) Patent urachus D) Omphalocele E) Gastroschisis
Answer: B
The vitelline (omphalomesenteric) duct connects the midgut to the yolk sac during early development and normally obliterates by week 8–9. If it persists, it forms a Meckel's diverticulum — a true diverticulum of the ileum containing all three layers of the bowel wall, located ~2 feet from the ileocaecal valve, often with ectopic gastric or pancreatic tissue.
📘 Q27 (Embryology) — The processus vaginalis is a diverticulum of the peritoneum that accompanies the: A) Round ligament through the inguinal canal B) Gubernaculum through the inguinal canal C) Spermatic cord through the inguinal canal D) Ureter into the pelvis E) Fallopian tube into the broad ligament
Answer: B
The processus vaginalis is an outpouching of the parietal peritoneum that precedes the descent of the testis through the inguinal canal, guided by the gubernaculum. In females, a small remnant (canal of Nuck) may persist. Incomplete obliteration of the processus vaginalis in males leads to indirect inguinal hernia or hydrocele.
📘 Q28 (Embryology) — The correct sequence of pre-embryonic development is: A) Morula → blastocyst → zygote → gastrula B) Zygote → morula → blastocyst → gastrula C) Zygote → blastocyst → morula → gastrula D) Zygote → gastrula → morula → blastocyst E) Blastocyst → zygote → morula → gastrula
Answer: B
After fertilisation, the zygote undergoes cleavage divisions to form a morula (solid ball of 16–32 cells at day 3–4). The morula develops into a blastocyst (with an inner cell mass and blastocyst cavity) around day 5. Gastrulation occurs in week 3, forming the three germ layers (ectoderm, mesoderm, endoderm).
📘 Q29 (Embryology) — The mechanism by which the spermatozoon and oocyte membranes fuse is mediated by: A) ZP3 receptor binding B) Acrosin release C) Binding of sperm Izumo1 to oocyte Juno (Folr4) D) CD9 on the sperm surface E) Hyaluronidase activity
Answer: C
Izumo1 is a transmembrane protein on the sperm surface that binds specifically to its receptor Juno (Folr4) on the oocyte membrane. This interaction is essential for gamete fusion. CD9 is a tetraspanin on the oocyte membrane that also participates in fusion. After fusion, the cortical reaction blocks polyspermy.
📘 Q30 (Embryology) — The primary embryonic inducer of kidney development is: A) The metanephric mesenchyme B) The ureteric bud C) The pronephros D) The mesonephros E) The cloaca
Answer: B
The definitive kidney (metanephros) develops from reciprocal induction between the ureteric bud (an outgrowth of the mesonephric duct) and the metanephric mesenchyme. The ureteric bud branches to form the collecting ducts, renal pelvis, and ureters, while the metanephric mesenchyme differentiates into nephrons. Failure of ureteric bud development results in renal agenesis.
📘 Q31 (Embryology) — Which immunoglobulin is selectively transported across the syncytiotrophoblast to provide passive immunity to the fetus? A) IgA B) IgG C) IgM D) IgE E) IgD
Answer: B
IgG is the only immunoglobulin class that is actively transported across the syncytiotrophoblast via neonatal Fc receptors (FcRn). This transplacental transfer begins around 13–16 weeks and increases through the third trimester, providing the newborn with protection against infections during the first months of life. IgM, IgA, IgE, and IgD do not cross the placenta.
📘 Q32 (Embryology) — The cervical epithelium undergoes a squamocolumnar junction. The original squamocolumnar junction is located at: A) The external os B) The internal os C) In the endocervical canal D) At the transformation zone E) On the ectocervix
Answer: A
At birth, the squamocolumnar junction (SCJ) lies at the external os. During puberty and pregnancy, oestrogen causes eversion of columnar epithelium onto the ectocervix (ectropion). The subsequent process of squamous metaplasia forms the transformation zone. Most cervical intraepithelial neoplasia and cervical cancers arise at the transformation zone.
📘 Q33 (Embryology) — The ovarian surface epithelium is derived from: A) Mesonephric duct B) Paramesonephric duct C) Coelomic epithelium (mesothelium) D) Primordial germ cells E) Neural crest
Answer: C
The ovaries develop from three embryonic sources: the coelomic epithelium (surface epithelium), the underlying mesenchyme (ovarian stroma), and the primordial germ cells (from the yolk sac endoderm). The surface epithelium of the ovary is thus derived from coelomic epithelium, and it is this epithelium that gives rise to the majority of epithelial ovarian cancers.
Genetics
📘 Q34 (Genetics) — Which of the following best describes the structure of a nucleosome? A) DNA wrapped around a core of eight histone proteins (H2A, H2B, H3, H4 each ×2) B) DNA wrapped around histone H1 alone C) RNA wrapped around a single histone tetramer D) A double-stranded DNA helix with no associated proteins E) Chromatin fibres coiled into heterochromatin
Answer: A
The nucleosome is the fundamental unit of chromatin. It consists of ~147 base pairs of DNA wrapped approximately 1.7 turns around a histone octamer (two molecules each of H2A, H2B, H3, and H4). Histone H1 binds the linker DNA between nucleosomes, stabilising higher-order chromatin folding.
📘 Q35 (Genetics) — The process by which mRNA is synthesised from a DNA template is called: A) Translation B) Replication C) Transcription D) Splicing E) Transduction
Answer: C
Transcription is the process by which RNA polymerase II synthesises pre-mRNA complementary to a DNA template. The pre-mRNA undergoes post-transcriptional modifications including 5′ capping, 3′ polyadenylation, and splicing (removal of introns) to form mature mRNA, which is then translated into protein in the cytoplasm.
📘 Q36 (Genetics) — The start codon (AUG) codes for which amino acid? A) Tryptophan B) Methionine C) Valine D) Leucine E) Arginine
Answer: B
AUG is the universal start codon that codes for methionine (Met). In eukaryotes, this initiates translation. Methionine is also encoded by a single triplet, making it unique among the 20 standard amino acids. The stop codons (UAA, UAG, UGA) do not code for any amino acid.
📘 Q37 (Genetics) — A frameshift mutation results from: A) Substitution of a single base B) Deletion or insertion of a number of bases not divisible by 3 C) Deletion of an entire exon D) A point mutation in a non-coding region E) Expansion of a trinucleotide repeat
Answer: B
Frameshift mutations occur when the number of inserted or deleted bases is not a multiple of three, shifting the reading frame for all downstream codons. This usually leads to premature stop codons and a truncated, non-functional protein. A single base substitution (missense or nonsense) is a point mutation that does not shift the reading frame.
📘 Q38 (Genetics) — The human genome contains approximately how many protein-coding genes? A) ~5,000 B) ~20,000 C) ~50,000 D) ~100,000 E) ~200,000
Answer: B
The Human Genome Project revealed that there are approximately 20,000–25,000 protein-coding genes in the human genome. This represents less than 2% of the total genomic DNA. The remainder includes non-coding RNA genes, regulatory elements, introns, repetitive sequences, and other functional elements.
📘 Q39 (Genetics) — Epigenetic modification that typically silences gene expression involves: A) Acetylation of histone lysine residues B) Methylation of CpG islands in promoter regions C) Phosphorylation of histone serine residues D) Ubiquitination of histones E) ADP-ribosylation of transcription factors
Answer: B
DNA methylation at CpG dinucleotides in promoter regions is a key epigenetic silencing mechanism. Methylated CpG islands recruit methyl-binding domain proteins and histone deacetylases, leading to condensed chromatin (heterochromatin) and transcriptional repression. Histone acetylation (option A) is associated with active transcription, not silencing.
📘 Q40 (Genetics) — Genomic imprinting is best described as: A) Inheritance of mitochondrial DNA from both parents B) Expression of a gene depending on its parental origin C) Inactivation of one X chromosome in females D) Silencing of both alleles of a tumour suppressor gene E) Mutation in the coding sequence of a gene
Answer: B
Genomic imprinting is an epigenetic phenomenon where certain genes are expressed in a parent-of-origin-specific manner. Imprinted genes are silenced by DNA methylation and histone modifications during gametogenesis. Examples include IGF2 (expressed from paternal allele) and H19 (expressed from maternal allele). Imprinting disorders include Beckwith-Wiedemann syndrome and Prader-Willi/Angelman syndromes.
📘 Q41 (Genetics) — A normal human female karyotype is written as: A) 46,XY B) 46,XX C) 45,X D) 47,XX,+21 E) 46,XX,del(5q)
Answer: B
The standard human karyotype notation lists the total chromosome number followed by the sex chromosome constitution. A normal female is 46,XX (46 chromosomes including two X chromosomes). A normal male is 46,XY. The other options represent Turner syndrome (45,X), Down syndrome (47,XX,+21), and a deletion of the long arm of chromosome 5 (46,XX,del(5q)).
📘 Q42 (Genetics) — Turner syndrome most commonly results from: A) 47,XXY B) 45,X C) 47,XXX D) 46,XXp- E) 46,XY
Answer: B
Turner syndrome is caused by complete or partial absence of a second sex chromosome, most commonly 45,X (monosomy X). The missing chromosome is usually of paternal origin (X or Y). Mosaic forms (e.g., 45,X/46,XX) also occur. Clinical features include short stature, webbed neck, shield chest, primary amenorrhoea, and gonadal dysgenesis.
📘 Q43 (Genetics) — A Robertsonian translocation between chromosomes 14 and 21 in a phenotypically normal parent confers what risk of having a child with Down syndrome? A) <1% B) 1–2% C) 5–15% D) 50% E) 100%
Answer: C
A carrier of a balanced Robertsonian translocation involving chromosomes 14 and 21 has a theoretical risk of 1 in 3 of having a child with translocation Down syndrome, but empirical data show a risk of ~10–15% when the mother is the carrier and ~1–2% when the father is the carrier. This is because unbalanced gametes arise during meiosis.
📘 Q44 (Genetics) — The recurrence risk for a couple who have had one child with an autosomal recessive condition such as cystic fibrosis is: A) 1 in 2 (50%) B) 1 in 4 (25%) C) 1 in 8 (12.5%) D) 1 in 100 (1%) E) 2 in 3 (67%)
Answer: B
For autosomal recessive conditions, both parents are obligate carriers. In each pregnancy, the risk that the child is affected (inherits two mutant alleles) is 1 in 4 (25%). The risk of being a carrier (one mutant allele) is 1 in 2 (50%), and the risk of being homozygous normal is 1 in 4 (25%).
📘 Q45 (Genetics) — In X-linked recessive inheritance, an affected father and a carrier mother have what chance of having an affected son? A) 0% B) 25% C) 50% D) 75% E) 100%
Answer: C
An affected father passes his X chromosome (with the mutation) to all daughters (who become carriers) and his Y chromosome to all sons (who are unaffected by paternal inheritance). However, the mother is a carrier and has a 50% chance of passing the mutant X to a son. Therefore, the chance of an affected son is 50%. All daughters will be carriers (if they inherit the father's X) or affected (if they also inherit the mother's mutant X).
📘 Q46 (Genetics) — Mitochondrial inheritance is characterised by: A) Transmission only through males B) Transmission only through females C) Equal transmission through both parents D) Recombination of mitochondrial DNA E) X-linked dominant pattern
Answer: B
Mitochondrial DNA is inherited exclusively from the mother because the sperm's mitochondria are degraded after fertilisation (or do not enter the oocyte). Mitochondrial disorders show maternal inheritance: all children of an affected female may inherit the mutation, but only females pass it on. Examples include Leber's hereditary optic neuropathy (LHON) and MELAS syndrome.
📘 Q47 (Genetics) — The triple test for Down syndrome screening typically measures: A) hCG, AFP, and oestriol B) hCG, AFP, and inhibin A C) hCG, inhibin A, and PAPP-A D) AFP, oestriol, and PAPP-A E) hCG, progesterone, and oestradiol
Answer: A
The second-trimester triple test (used at 15–20 weeks) measures maternal serum alpha-fetoprotein (AFP), human chorionic gonadotrophin (hCG), and unconjugated oestriol (uE3). In Down syndrome, AFP and oestriol are decreased, while hCG is increased. The quadruple test adds inhibin A (increased) for improved sensitivity.
📘 Q48 (Genetics) — Cell-free fetal DNA (cffDNA) in maternal blood is derived primarily from: A) Maternal leukocytes B) Fetal erythrocytes C) Apoptotic syncytiotrophoblast cells D) Amniotic fluid cells E) Fetal hepatocytes
Answer: C
Cell-free fetal DNA in maternal circulation originates predominantly from apoptosis of syncytiotrophoblast cells. It is detectable from ~4 weeks' gestation, but sufficient levels for non-invasive prenatal testing (NIPT) are present from ~10 weeks. cffDNA represents ~5–20% of total cell-free DNA in maternal plasma and is cleared within hours after delivery.
📘 Q49 (Genetics) — The most common trinucleotide repeat disorder in obstetric practice is: A) Huntington disease (CAG repeat, chromosome 4) B) Fragile X syndrome (CGG repeat, chromosome X) C) Myotonic dystrophy (CTG repeat, chromosome 19) D) Friedreich ataxia (GAA repeat, chromosome 9) E) Spinocerebellar ataxia (CAG repeat)
Answer: B
Fragile X syndrome is the most common inherited cause of intellectual disability and is caused by CGG trinucleotide repeat expansion in the FMR1 gene on the X chromosome. Premutation carriers (55–200 repeats) are at risk of fragile X-associated primary ovarian insufficiency (FXPOI) and fragile X-associated tremor/ataxia syndrome (FXTAS). Full mutation (>200 repeats) causes gene silencing.
📘 Q50 (Genetics) — Sickle cell disease is caused by a point mutation in the β-globin gene that results in: A) Substitution of valine for glutamic acid at position 6 B) Substitution of glutamic acid for valine at position 6 C) Deletion of a single base in the coding sequence D) Insertion of an extra amino acid in the β chain E) Premature stop codon in the β-globin gene
Answer: A
Sickle cell disease results from an A → T transversion in the HBB gene, leading to substitution of valine (a hydrophobic amino acid) for glutamic acid (a hydrophilic one) at the 6th position of the β-globin chain (Glu6Val). This causes haemoglobin S to polymerise under deoxygenated conditions, distorting red blood cells into a sickle shape.
📘 Q51 (Genetics) — The coefficient of relationship between a woman and her maternal grandmother is: A) 1.0 (100%) B) 0.5 (50%) C) 0.25 (25%) D) 0.125 (12.5%) E) 0.0625 (6.25%)
Answer: C
The coefficient of relationship (r) represents the proportion of shared genes by descent. A woman shares 50% of her genes with each parent, and each parent shares 50% with their parents. Thus, the coefficient between a woman and her grandmother is 0.5 × 0.5 = 0.25 (25%).
📘 Q52 (Genetics) — Aneuploidy most commonly arises from: A) Deletion during DNA replication B) Spindle checkpoint failure, during maternal meiosis I C) Crossing over between homologous chromosomes D) Mutation in a tumour suppressor gene E) Telomere shortening
Answer: B
Most aneuploidies (e.g., trisomy 21, 18, 13) result from non-disjunction during maternal meiosis I, which is strongly associated with advancing maternal age. The spindle assembly checkpoint fails to detect improper chromosome attachment, leading to unequal segregation of homologous chromosomes. Paternal meiotic errors are less common.
📘 Q53 (Genetics) — The phenomenon of variable expressivity refers to: A) Some individuals with a mutation not showing any features of the condition B) A wide range of clinical severity among individuals with the same genotype C) Increasing severity of a condition in successive generations D) Expression of a mutant allele only in one sex E) Two different mutations in the same gene causing different phenotypes
Answer: B
Variable expressivity describes the range of clinical features and severity seen in individuals with the same genetic condition. For example, neurofibromatosis type 1 (NF1) can manifest with only café-au-lait spots in one family member and multiple neurofibromas, optic gliomas, and skeletal abnormalities in another. This differs from non-penetrance (option A), where a mutation carrier shows no features.
📘 Q54 (Genetics) — A balanced translocation carrier has: A) Normal phenotype but abnormal karyotype with 45 chromosomes B) Normal phenotype and normal karyotype C) Normal phenotype but abnormal karyotype with the correct total chromosome count D) Abnormal phenotype and abnormal karyotype E) Normal karyotype but reduced fertility
Answer: C
A balanced translocation carrier has all the genetic material present but redistributed between chromosomes. The total chromosome number may be 45 if the translocation is Robertsonian (two acrocentric chromosomes fuse), but there is no net loss of genetic material, so the phenotype is usually normal. However, they are at increased risk of producing unbalanced gametes.
📘 Q55 (Genetics) — The Hardy–Weinberg principle predicts that for a population in equilibrium, the frequency of heterozygous carriers of a recessive condition is given by: A) p² + 2pq B) 2pq C) q² D) p² E) (p + q)²
Answer: B
In Hardy–Weinberg equilibrium, p is the frequency of the dominant allele and q the frequency of the recessive allele (p + q = 1). The genotype frequencies are p² (homozygous dominant), 2pq (heterozygous carriers), and q² (homozygous recessive affected individuals). For a recessive condition with incidence q², the carrier frequency is 2pq ≈ 2q (since p ≈ 1).
📘 Q56 (Genetics) — RNA interference (RNAi) involves silencing of gene expression through: A) Binding of small interfering RNA (siRNA) to complementary mRNA, leading to its degradation B) Methylation of promoter CpG islands C) Acetylation of histones in the coding region D) Deletion of the target gene E) Inhibition of RNA polymerase II
Answer: A
RNA interference is a post-transcriptional gene silencing mechanism triggered by double-stranded RNA. Dicer cleaves dsRNA into small interfering RNAs (siRNAs) ~21–23 nucleotides long, which are loaded into the RNA-induced silencing complex (RISC). The siRNA guides RISC to complementary mRNA, leading to mRNA cleavage and degradation, thus preventing translation.
📘 Q57 (Genetics) — A missense mutation is one that: A) Changes a codon to a stop codon B) Changes a codon to specify a different amino acid C) Does not change the amino acid sequence D) Deletes a segment of the gene E) Inserts an extra base
Answer: B
A missense mutation is a single nucleotide substitution that results in a codon coding for a different amino acid. The functional consequence depends on the nature of the amino acid change (conservative vs. non-conservative) and the location in the protein. A nonsense mutation (option A) creates a premature stop codon.
📘 Q58 (Genetics) — Cystic fibrosis is caused by mutations in the CFTR gene located on: A) Chromosome 4 B) Chromosome 7 C) Chromosome 12 D) Chromosome X E) Chromosome 21
Answer: B
The CFTR (cystic fibrosis transmembrane conductance regulator) gene is located on the long arm of chromosome 7 (7q31.2). The most common mutation is ΔF508 (deletion of phenylalanine at position 508), found in ~70% of CF chromosomes in Northern European populations. The gene encodes a chloride channel protein essential for epithelial fluid secretion.
📘 Q59 (Genetics) — Uniparental disomy (UPD) is defined as: A) Two identical copies of a chromosome from one parent and none from the other B) Both copies of a chromosome inherited from the same parent C) A single copy of a chromosome from both parents D) An extra copy of a chromosome from both parents E) Loss of both copies of a chromosome
Answer: B
Uniparental disomy (UPD) occurs when an individual inherits both copies of a specific chromosome from one parent and no copy from the other parent. Heterodisomy (inheriting two different homologues from one parent) results from meiotic non-disjunction with trisomy rescue. Isodisomy (identical copies) can lead to recessive disease. UPD can cause imprinting disorders such as Prader-Willi and Angelman syndromes.
📘 Q60 (Genetics) — The most common aneuploidy at term is: A) Trisomy 21 (47,+21) B) Trisomy 18 (47,+18) C) Trisomy 13 (47,+13) D) 45,X E) 47,XXY
Answer: A
Trisomy 21 (Down syndrome) is the most common autosomal aneuploidy at term, with an incidence of ~1 in 800 live births. The risk increases with maternal age. Trisomy 18 and trisomy 13 are rarer (1 in 5,000 and 1 in 15,000, respectively) and have much higher rates of intrauterine lethality. 45,X (Turner syndrome) is common among miscarriages but rare among live births.
📘 Q61 (Genetics) — In a pedigree demonstrating autosomal dominant inheritance with complete penetrance, an affected individual with one affected parent has what chance of passing the mutation to each child? A) 1 in 4 (25%) B) 1 in 2 (50%) C) 2 in 3 (67%) D) 3 in 4 (75%) E) Virtually 100%
Answer: B
In autosomal dominant inheritance, the affected individual is heterozygous for the mutant allele. For each pregnancy, there is a 50% chance of passing the mutant allele (resulting in an affected child) and a 50% chance of passing the normal allele (resulting in an unaffected child). Male-to-male transmission rules out X-linked inheritance.
📘 Q62 (Genetics) — The Philadelphia chromosome, t(9;22)(q34;q11), is associated with: A) Acute lymphoblastic leukaemia B) Chronic myeloid leukaemia C) Breast cancer D) Retinoblastoma E) Osteosarcoma
Answer: B
The Philadelphia chromosome is a reciprocal translocation between chromosomes 9 and 22, t(9;22)(q34;q11), creating a BCR-ABL1 fusion gene on the derivative chromosome 22. This encodes a constitutively active tyrosine kinase that drives uncontrolled proliferation in chronic myeloid leukaemia (CML). It is also found in some cases of acute lymphoblastic leukaemia (ALL).
📘 Q63 (Genetics) — Prenatal screening for aneuploidies using cell-free fetal DNA (NIPT) has the highest sensitivity for which condition? A) Trisomy 13 B) Trisomy 18 C) Trisomy 21 D) Turner syndrome E) Triploidy
Answer: C
Non-invasive prenatal testing (NIPT) using cell-free fetal DNA has the highest sensitivity and specificity for trisomy 21 (Down syndrome), with detection rates >99% and a false-positive rate <0.1%. Sensitivity is slightly lower for trisomy 18 (~97%) and trisomy 13 (~90%), and lower still for sex chromosome aneuploidies.
📘 Q64 (Genetics) — BRCA1 and BRCA2 are: A) Proto-oncogenes associated with sporadic breast cancer B) Tumour suppressor genes involved in homologous recombination repair of double-strand DNA breaks C) Oncogenes involved in signal transduction D) DNA repair genes involved in mismatch repair E) Genes encoding epidermal growth factor receptor
Answer: B
BRCA1 and BRCA2 are tumour suppressor genes that encode proteins essential for homologous recombination repair of DNA double-strand breaks. Loss-of-function mutations predispose to breast, ovarian, pancreatic, and prostate cancers. They follow an autosomal dominant inheritance pattern with reduced penetrance. PARP inhibitors exploit synthetic lethality in BRCA-mutated cancers.
📘 Q65 (Genetics) — The phenomenon of anticipation occurs in which type of genetic disorder? A) Autosomal recessive B) Autosomal dominant disorders caused by trinucleotide repeat expansions C) X-linked recessive D) Mitochondrial E) Chromosomal translocation carriers
Answer: B
Anticipation refers to the increase in disease severity or earlier age of onset in successive generations. It is characteristic of trinucleotide repeat expansion disorders such as Huntington disease (CAG repeats), myotonic dystrophy (CTG repeats), and Fragile X syndrome (CGG repeats). The repeat number tends to expand during meiosis, particularly through the paternal line in some disorders.
📘 Q66 (Genetics) — The Hardy–Weinberg equilibrium requires all of the following EXCEPT: A) Random mating B) No mutation C) Natural selection D) Large population size E) No gene flow
Answer: C
The Hardy–Weinberg equilibrium assumes no selection, no mutation, random mating, a large population (no genetic drift), and no gene flow (migration). Natural selection violates the equilibrium because it alters allele frequencies. The model describes ideal conditions under which genotype frequencies remain constant from one generation to the next.
📘 Q67 (Genetics) — A chorionic villus sampling (CVS) karyotype shows 46,XX/45,X mosaicism. The most likely explanation for the 45,X cell line is: A) Unbalanced translocation B) Mitotic non-disjunction in the early embryo C) Robertsonian translocation D) Deletion of the short arm of the X chromosome E) Meiotic non-disjunction
Answer: B
Mosaicism arises from a post-zygotic (mitotic) error. In this case, a normal 46,XX zygote underwent non-disjunction during an early cleavage division, producing a 45,X cell line (loss of an X chromosome) and a 46,XX cell line. The clinical phenotype depends on the proportion of abnormal cells in different tissues.
📘 Q68 (Genetics) — Microdeletion of chromosome 22q11.2 is associated with: A) DiGeorge syndrome (velocardiofacial syndrome) B) Cri-du-chat syndrome C) Wolf-Hirschhorn syndrome D) Williams syndrome E) Prader-Willi syndrome
Answer: A
The 22q11.2 microdeletion is the most common microdeletion syndrome, affecting ~1 in 4,000 live births. It causes DiGeorge syndrome (now often called 22q11.2 deletion syndrome), characterised by cardiac outflow tract anomalies, palatal defects, thymic hypoplasia/aplasia (with T-cell immunodeficiency), hypocalcaemia (due to parathyroid hypoplasia), and typical facial features.
📘 Q69 (Genetics) — The phenomenon of pleiotropy refers to: A) One gene causing multiple seemingly unrelated phenotypic effects B) Multiple genes influencing a single trait C) A single gene having no observable effect D) Interaction between two different genes E) Variable expression of a gene in different tissues
Answer: A
Pleiotropy occurs when a single gene mutation produces multiple, often apparently unrelated, phenotypic effects. For example, mutations in the fibrillin-1 gene (FBN1) cause Marfan syndrome, which affects the skeletal system (tall stature, arachnodactyly), cardiovascular system (aortic root dilation), eyes (lens dislocation), and lungs. Polygenic inheritance (option B) is the opposite concept.
📘 Q70 (Genetics) — A woman with a 47,XXX karyotype is most likely to have which clinical presentation? A) Primary amenorrhoea B) Infertility C) Normal phenotype with possible learning difficulties D) Severe intellectual disability E) Short stature
Answer: C
The 47,XXX (trisomy X) karyotype is often associated with a normal or near-normal phenotype. Many women are undiagnosed. Features may include tall stature, mild learning difficulties or speech delay, and normal fertility. Unlike Turner syndrome (45,X), there is no short stature or gonadal dysgenesis. It is often discovered incidentally during prenatal diagnosis for other reasons.
📘 Q71 (Genetics) — The most common cause of α-thalassaemia in South Asian populations is: A) Point mutation in the α-globin gene B) Deletion of one or both α-globin genes C) Duplication of the γ-globin gene D) Trinucleotide repeat expansion E) Translocation involving chromosome 16
Answer: B
α-Thalassaemia is most commonly caused by deletions involving the α-globin gene cluster on chromosome 16. There are normally two α-globin genes (α1 and α2) on each chromosome 16. Loss of one gene (α-thalassaemia trait) results in mild microcytic anaemia; loss of all four genes (Hb Bart's hydrops fetalis) is lethal in utero. Point mutations causing α-thalassaemia are rarer.
📘 Q72 (Genetics) — Which of the following correctly describes a CpG island? A) A cluster of C–G base pairs in the coding region B) A GC-rich region often located in gene promoter regions C) A region where guanine is replaced by inosine D) A region of telomeric repeats E) A centromeric satellite sequence
Answer: B
CpG islands are genomic regions with a high density of cytosine–guanine dinucleotides (CpG). They are typically 300–3,000 bp long and are found in the promoter regions of ~60–70% of human genes. CpG islands are usually unmethylated in active genes; hypermethylation leads to transcriptional silencing, a common epigenetic alteration in cancer.
Pathology
📘 Q73 (Pathology) — The morphological hallmark of irreversible cell injury is: A) Cellular swelling B) Fatty change C) Pyknosis, karyorrhexis, and karyolysis of the nucleus D) Formation of blebs on the plasma membrane E) Swelling of the endoplasmic reticulum
Answer: C
Irreversible cell injury is characterised by definitive nuclear changes: pyknosis (nuclear shrinkage and hyperchromasia), karyorrhexis (nuclear fragmentation), and karyolysis (dissolution of the nucleus by DNases). Cellular swelling and bleb formation (options A and D) occur in reversible injury. Once nuclear changes are evident, cell death is inevitable.
📘 Q74 (Pathology) — Apoptosis is characterised by all of the following EXCEPT: A) Cell shrinkage and membrane blebbing B) Activation of caspases C) Inflammation of surrounding tissue D) DNA laddering on electrophoresis E) Formation of apoptotic bodies
Answer: C
Apoptosis is programmed cell death that is carefully regulated and does not trigger inflammation. Apoptotic bodies are phagocytosed by macrophages and adjacent cells without release of pro-inflammatory mediators. In contrast, necrosis (accidental cell death) causes release of cellular contents and elicits an inflammatory response. DNA laddering is characteristic of apoptosis due to internucleosomal cleavage.
📘 Q75 (Pathology) — Caseous necrosis is most characteristically seen in: A) Myocardial infarction B) Tuberculous infection C) Acute pancreatitis D) Cerebral infarction E) Fat necrosis of the breast
Answer: B
Caseous necrosis is a distinctive form of coagulative necrosis with a "cheese-like" gross appearance and amorphous, eosinophilic, granular debris microscopically surrounded by granulomatous inflammation. It is most characteristic of Mycobacterium tuberculosis infection. Fat necrosis (option E) occurs in acute pancreatitis or breast trauma and results from enzymatic digestion of fat.
📘 Q76 (Pathology) — The earliest histological change in acute inflammation is: A) Emigration of neutrophils B) Vasodilation of arterioles C) Increased vascular permeability D) Margination of leukocytes E) Phagocytosis
Answer: B
The initial event in acute inflammation is transient vasoconstriction followed by vasodilation of arterioles, which increases blood flow (causing erythema and warmth). This is mediated by histamine, nitric oxide, and prostaglandins. Subsequently, increased vascular permeability occurs, followed by leukocyte margination, emigration (mainly neutrophils), and phagocytosis.
📘 Q77 (Pathology) — The predominant cell type in chronic inflammation is the: A) Neutrophil B) Eosinophil C) Macrophage D) Basophil E) Mast cell
Answer: C
Chronic inflammation is characterised by infiltration of mononuclear cells, primarily macrophages, lymphocytes, and plasma cells. Macrophages are key orchestrators, releasing cytokines and growth factors that drive fibrosis and tissue remodelling. Neutrophils are the hallmark of acute inflammation, though they may also be present in some forms of chronic inflammation.
📘 Q78 (Pathology) — Granulation tissue is composed of: A) Fibroblasts, collagen, and myofibroblasts only B) Proliferating small blood vessels, fibroblasts, and inflammatory cells C) Dense collagen with no vascular component D) Mature scar tissue E) Epithelial cells and basement membrane
Answer: B
Granulation tissue is the hallmark of the proliferative phase of wound healing. It consists of newly formed capillaries (angiogenesis), proliferating fibroblasts, and mixed inflammatory cells (macrophages, lymphocytes) embedded in a loose extracellular matrix. It appears grossly as pink, soft, granular tissue. Over time, it matures into a hypocellular, avascular scar.
📘 Q79 (Pathology) — Keloid formation differs from hypertrophic scar in that keloids: A) Remain within the boundaries of the original wound B) Extend beyond the margins of the original wound and rarely regress C) Are more common in children than adults D) Contain more myofibroblasts E) Are associated with excessive contraction
Answer: B
Keloids are abnormal wound healing responses in which scar tissue extends beyond the original wound margins, invading adjacent normal skin. Hypertrophic scars are raised but remain within the wound boundaries and often regress over time. Keloids are more common in dark-skinned individuals and may be genetically predisposed. They rarely regress spontaneously and tend to recur after excision.
📘 Q80 (Pathology) — The single best prognostic indicator for invasive breast cancer is: A) Tumour size B) Oestrogen receptor status C) Lymph node status D) Histological grade E) HER2/neu overexpression
Answer: C
Axillary lymph node involvement is the single most important prognostic factor in invasive breast cancer. The number of positive nodes correlates inversely with survival. Tumour size, histological grade, and receptor status are also important prognostic factors, but nodal status remains the strongest independent predictor of outcome.
📘 Q81 (Pathology) — The most common type of ovarian germ cell tumour is: A) Dysgerminoma B) Yolk sac tumour C) Mature cystic teratoma (dermoid cyst) D) Immature teratoma E) Choriocarcinoma
Answer: C
Mature cystic teratoma (dermoid cyst) is the most common ovarian germ cell tumour and the most common ovarian tumour in reproductive-age women. It is benign, composed of well-differentiated tissues from all three germ layers (ectoderm, mesoderm, endoderm). Ectodermal elements (skin, hair, sebaceous glands) predominate. It accounts for ~20% of all ovarian neoplasms.
📘 Q82 (Pathology) — Endometrioid adenocarcinoma of the ovary is most commonly associated with: A) BRCA1 mutation B) Endometriosis C) Lynch syndrome D) Obesity E) HPV infection
Answer: B
Endometrioid ovarian carcinoma frequently arises in association with endometriosis (malignant transformation of endometriotic cysts). It is the second most common type of epithelial ovarian cancer (after high-grade serous carcinoma). It is morphologically similar to endometrioid endometrial cancer and has a relatively favourable prognosis compared to serous carcinoma.
📘 Q83 (Pathology) — The most common cervical cancer worldwide is: A) Adenocarcinoma B) Squamous cell carcinoma C) Small cell carcinoma D) Clear cell carcinoma E) Sarcoma
Answer: B
Squamous cell carcinoma accounts for approximately 70–80% of cervical cancers worldwide. It arises from the transformation zone at the squamocolumnar junction and is strongly associated with high-risk human papillomavirus (HPV) types, particularly HPV-16 and HPV-18. Adenocarcinoma (option A) accounts for 15–20% and is also HPV-associated, though its incidence is rising.
📘 Q84 (Pathology) — Koilocytotic atypia on cervical cytology is characteristic of: A) Endocervical adenocarcinoma B) HPV infection (low-grade squamous intraepithelial lesion, LSIL) C) Squamous metaplasia D) Endometritis E) Atrophic vaginitis
Answer: B
Koilocytes are squamous epithelial cells with characteristic perinuclear halos (clear cytoplasmic vacuolisation), nuclear enlargement, hyperchromasia, and irregular nuclear membranes. They are the cytopathic effect of HPV replication and are diagnostic of LSIL (CIN 1). The presence of koilocytes indicates productive HPV infection. They are not seen in adenocarcinoma or metaplasia.
📘 Q85 (Pathology) — The most common uterine malignancy is: A) Leiomyosarcoma B) Endometrial stromal sarcoma C) Endometrioid adenocarcinoma D) Carcinosarcoma (malignant mixed Müllerian tumour) E) Squamous cell carcinoma of the cervix
Answer: C
Endometrioid adenocarcinoma is the most common uterine malignancy, accounting for ~80–90% of endometrial cancers. It is associated with unopposed oestrogen stimulation (type I endometrial cancer) and has a favourable prognosis when diagnosed early. Endometrial cancer is the most common gynaecological malignancy in developed countries.
📘 Q86 (Pathology) — Which of the following is a well-established risk factor for endometrial hyperplasia and carcinoma? A) Multiparity B) Oral contraceptive use C) Unopposed oestrogen therapy D) Smoking E) Progestin-only contraception
Answer: C
Unopposed oestrogen (from exogenous sources or endogenous production due to anovulation, obesity, or oestrogen-secreting tumours) is a major risk factor for endometrial hyperplasia and type I endometrial carcinoma. Progestins oppose oestrogen's mitogenic effect on the endometrium, which is why the combined oral contraceptive pill and progestin therapy are protective.
📘 Q87 (Pathology) — The most common cause of abnormal uterine bleeding in premenopausal women is: A) Endometrial carcinoma B) Endometrial polyp C) Leiomyoma (fibroid) D) Dysfunctional uterine bleeding (ovulatory dysfunction) E) Adenomyosis
Answer: D
Dysfunctional uterine bleeding (DUB), now termed abnormal uterine bleeding due to ovulatory dysfunction (AUB-O), is the most common cause of AUB in premenopausal women. It results from anovulation or oligo-ovulation, leading to unopposed oestrogen stimulation and unpredictable endometrial shedding. Endometrial polyps, fibroids, and adenomyosis are structural causes (PALM-COEIN classification).
📘 Q88 (Pathology) — Hydatidiform mole is characterised by: A) Aneuploidy with monosomy X B) Diploid karyotype with both chromosome sets from the mother C) Diploid karyotype with both chromosome sets from the father D) Triploid karyotype E) Tetraploid karyotype
Answer: C
A complete hydatidiform mole (CHM) typically has a 46,XX karyotype in which all chromosomes are of paternal origin (androgenetic conception). This results from fertilisation of an enucleated ovum by a single sperm that subsequently doubles its chromosomes (46,XX). Partial hydatidiform mole (PHM) is triploid (69,XXY), with two paternal and one maternal haploid sets.
📘 Q89 (Pathology) — The most serious complication of a complete hydatidiform mole is: A) Vaginal haemorrhage B) Uterine perforation C) Choriocarcinoma (gestational trophoblastic neoplasia) D) Pre-eclampsia E) Hyperemesis gravidarum
Answer: C
Complete hydatidiform mole carries a 15–20% risk of progression to gestational trophoblastic neoplasia (GTN), including invasive mole and choriocarcinoma. Following evacuation, serial hCG monitoring is essential to detect persistent disease. Partial moles have a lower risk (~1–5%). Choriocarcinoma is a highly malignant tumour that is exquisitely chemosensitive.
📘 Q90 (Pathology) — The Schiller test in cervical examination uses: A) Acetic acid to identify acetowhite epithelium B) Lugol's iodine to identify glycogen-containing normal squamous epithelium C) Methylene blue to stain dysplastic cells D) Silver nitrate to identify abnormal blood vessels E) Haematoxylin to stain nuclear material
Answer: B
The Schiller test involves applying Lugol's iodine solution to the cervix. Normal mature squamous epithelium contains glycogen, which stains dark brown. Immature squamous metaplasia, columnar epithelium, and dysplastic epithelium lack glycogen and remain unstained (Schiller-negative or Schiller-positive, i.e., positive for abnormality). This test helps identify areas for colposcopic biopsy.
📘 Q91 (Pathology) — The most common site of endometriosis is the: A) Ovaries B) Uterosacral ligaments C) Pouch of Douglas D) Fallopian tubes E) Bladder
Answer: A
The ovaries are the most common site of endometriosis. Ovarian endometriosis often forms endometriomas (chocolate cysts) — cysts filled with old, dark brown, tarry blood. The uterosacral ligaments, pouch of Douglas, and fallopian tubes are also frequently involved. Endometriosis implants are functionally active and respond to hormonal cycles, causing pain and infertility.
📘 Q92 (Pathology) — Adenomyosis is defined as: A) Ectopic endometrial tissue outside the uterus B) Presence of endometrial glands and stroma within the myometrium C) Adenocarcinoma of the endometrium D) Benign glandular proliferation in the cervix E) Fibrosis of the myometrium
Answer: B
Adenomyosis is characterised by the presence of ectopic endometrial glands and stroma within the myometrium, surrounded by hypertrophic and hyperplastic smooth muscle. It may be diffuse or focal (adenomyoma). Symptoms include heavy menstrual bleeding (menorrhagia), dysmenorrhoea, and chronic pelvic pain. It is distinguished from endometriosis (option A) by its location within the myometrium.
📘 Q93 (Pathology) — An infarcted, oedematous placenta with a "mushy" texture and foul odour is most consistent with: A) Placenta accreta B) Chorioamnionitis C) Placental abruption D) Placenta previa E) Succenturiate lobe
Answer: B
Chorioamnionitis is an acute inflammation of the chorion and amnion, usually due to ascending bacterial infection from the vagina. The placenta appears oedematous, friable, and may have a foul odour. Histologically, there is neutrophilic infiltration of the fetal membranes and chorionic plate. It is associated with preterm prelabour rupture of membranes (PPROM) and preterm labour.
📘 Q94 (Pathology) — In salpingitis, the most common causative organism is: A) Escherichia coli B) Neisseria gonorrhoeae C) Chlamydia trachomatis D) Mycoplasma genitalium E) Group B Streptococcus
Answer: C
Chlamydia trachomatis is the most common cause of acute salpingitis and pelvic inflammatory disease (PID) in many populations. It is an obligate intracellular bacterium that causes chronic, often subclinical infection, leading to tubal factor infertility and ectopic pregnancy. Neisseria gonorrhoeae is also a significant but less common cause; it tends to cause more acute symptoms.
📘 Q95 (Pathology) — The most common type of vulval carcinoma is: A) Basal cell carcinoma B) Malignant melanoma C) Squamous cell carcinoma D) Adenocarcinoma E) Paget's disease of the vulva
Answer: C
Squamous cell carcinoma accounts for ~85–90% of vulval malignancies. It typically occurs in postmenopausal women and may be associated with lichen sclerosus, differentiated vulval intraepithelial neoplasia (dVIN), or HPV infection (usual-type VIN). Basal cell carcinoma (option A) is rare on the vulva, and malignant melanoma (option B) accounts for ~5% of vulval cancers.
📘 Q96 (Pathology) — The histological finding of Arias-Stella reaction in the endometrium is associated with: A) Ectopic pregnancy B) Anovulation C) Endometrial hyperplasia D) Progesterone therapy E) Chronic endometritis
Answer: A
The Arias-Stella reaction is a characteristic change in endometrial glands seen in pregnancy, particularly in ectopic pregnancy. It features marked nuclear enlargement, hyperchromasia (often with a "smudgy" appearance), and cytoplasmic vacuolation. These changes result from high levels of hCG and progesterone. It must not be mistaken for adenocarcinoma, as the cytological atypia can be striking.
📘 Q97 (Pathology) — A Bartholin's gland abscess is most commonly caused by: A) Streptococcus agalactiae B) Chlamydia trachomatis C) Anaerobic bacteria D) Escherichia coli E) Neisseria gonorrhoeae
Answer: D
Bartholin's gland abscesses are most commonly caused by Escherichia coli (and other Enterobacteriaceae), followed by anaerobic bacteria. Neisseria gonorrhoeae and Chlamydia trachomatis are more commonly associated with Bartholin's gland infection (acute bartholinitis) but are less frequently isolated from established abscesses than E. coli.
📘 Q98 (Pathology) — Necrosis of the myometrium during pregnancy due to excessive stretching is known as: A) Uterine rupture B) Uterine atony C) Couvelaire uterus D) Adenomyosis E) Uterine inversion
Answer: C
Couvelaire uterus (uteroplacental apoplexy) occurs when blood from a placental abruption extravasates into the myometrium, causing dissection and necrosis of uterine muscle fibres. The uterus becomes woody, tender, and non-contractile, potentially leading to postpartum haemorrhage. It may necessitate caesarean hysterectomy in severe cases.
📘 Q99 (Pathology) — The most common pathological finding in postpartum haemorrhage requiring hysterectomy is: A) Placenta accreta spectrum B) Uterine atony C) Uterine rupture D) Disseminated intravascular coagulation (DIC) E) Uterine fibroids
Answer: B
Uterine atony (failure of the myometrium to contract adequately after delivery) is the most common cause of postpartum haemorrhage overall and the most common indication for peripartum hysterectomy in some series. However, placenta accreta spectrum (PAS) is increasingly the leading cause of peripartum hysterectomy in many centres, particularly in women with a previous caesarean section and placenta praevia.
📘 Q100 (Pathology) — The most common ovarian tumour in postmenopausal women is: A) Mature cystic teratoma B) Serous cystadenoma C) High-grade serous carcinoma D) Fibroma E) Mucinous cystadenoma
Answer: B
Serous cystadenoma is the most common ovarian tumour across all age groups and in postmenopausal women. It is a benign epithelial tumour that accounts for ~20–25% of all ovarian neoplasms. High-grade serous carcinoma (option C) is the most common malignant ovarian tumour in postmenopausal women, but benign tumours are more common overall.
End of Mock Exam 12 — 100 Questions