Molecular Pathology Practice Questions

Q: A pedigree chart shows the following pattern of inheritance. What is the most likely mode of inheritance?

Autosomal recessive. ***Autosomal recessive*** - Characterized by **unaffected carrier parents** producing affected offspring, with the trait **skipping generations**. - Affects **both sexes equally** and typically shows a **horizontal pattern** within a single generation. *Autosomal dominant* - Shows a **vertical pattern** where affected individuals have at least one affected parent in each generation. - Does **not skip generations** and demonstrates continuous transmission from parent to child. *X-linked recessive* - Primarily affects **males** with a characteristic pattern of affected grandfathers passing the trait through **carrier daughters** to affected grandsons. - Shows **no male-to-male transmission** since fathers cannot pass X-linked traits to their sons. *X-linked dominant* - Affects **more females than males** and shows transmission from affected fathers to **all daughters** but no sons. - Demonstrates a **vertical pattern** with affected individuals in consecutive generations, unlike the skipping seen in autosomal recessive.

Q: The HER2/neu receptor plays a role in what?

Predicting therapeutic response. **Explanation:** The **HER2/neu (Human Epidermal Growth Factor Receptor 2)** is a proto-oncogene located on chromosome 17 [3]. Its overexpression occurs in approximately 15–20% of breast cancers and serves as a critical **predictive marker** [1]. **Why Option A is correct:** HER2 status is primarily used to **predict therapeutic response** to targeted therapies. Patients who are HER2-positive respond specifically to monoclonal antibodies like **Trastuzumab (Herceptin)** and Pertuzumab [1]. These drugs block the extracellular domain of the receptor, inhibiting downstream signaling that promotes cell proliferation. **Analysis of Incorrect Options:** * **Option B (Diagnosis):** Breast cancer is diagnosed via clinical examination, imaging (Mammography/USG), and confirmed by histopathology (Biopsy). HER2 is a molecular marker used *after* diagnosis to characterize the tumor. * **Option C (Screening):** Screening is done via Mammography in the general population. Molecular markers are never used for screening. * **Option D (Recurrence):** While HER2 positivity is associated with a more aggressive clinical course and higher risk of recurrence (prognostic value), its primary clinical utility in modern oncology is guiding the choice of therapy [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Prognostic vs. Predictive:** HER2 is both. It is **prognostic** (indicates poor prognosis/aggressive tumor) and **predictive** (indicates likely response to Trastuzumab) [1]. * **Testing Method:** Initial screening is done via **Immunohistochemistry (IHC)**. If IHC results are equivocal (2+), **FISH (Fluorescence In Situ Hybridization)** is the gold standard to confirm gene amplification [2]. * **Side Effect:** Trastuzumab is associated with **cardiotoxicity** (reversible decrease in LVEF), unlike anthracyclines which cause irreversible damage.

Q: Which of the following chromosomes is involved in Patau syndrome?

Chromosome 13. **Explanation:** **Patau syndrome** is a severe genetic disorder caused by **Trisomy 13** (the presence of an extra copy of chromosome 13). It is the least common and most severe of the three viable autosomal trisomies. The condition results from meiotic non-disjunction, most commonly associated with advanced maternal age. **Analysis of Options:** * **Option A (Chromosome 13): Correct.** Patau syndrome is characterized by a "triad" of clinical features: **Microphthalmia** (small eyes), **Cleft lip/palate**, and **Polydactyly** (extra fingers/toes). Other features include holoprosencephaly and cutis aplasia (scalp defects). * **Option B (Chromosome 18): Incorrect.** Trisomy 18 is **Edwards syndrome**. Clinical hallmarks include "rocker-bottom feet," clenched fists with overlapping fingers, and micrognathia (small jaw). * **Option C (Chromosome 21): Incorrect.** Trisomy 21 is **Down syndrome**, the most common viable trisomy. It is characterized by intellectual disability, flat facial profile, Simian crease, and an increased risk of early-onset Alzheimer’s and ALL/AML. * **Option D (Chromosome 5): Incorrect.** A terminal deletion of the short arm of chromosome 5 (5p-) leads to **Cri-du-chat syndrome**, characterized by a high-pitched, cat-like cry and microcephaly. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Trisomies:** **P**atau (13 - **P**uberty starts at 13), **E**dwards (18 - **E**lection age is 18), **D**own (21 - **D**rinking age is 21). * **Biochemical Screening:** In Patau syndrome, first-semester screening typically shows **decreased free β-hCG and PAPP-A**. * **Prognosis:** Most infants with Patau syndrome die within the first few days or months of life due to severe neurological or cardiac complications.

Q: Which of the following chromosomal abnormalities is indicated by the chromosomal mapping?

Klinefelter syndrome. ***Klinefelter syndrome*** - The karyotype **47,XXY** shows an extra X chromosome in males, which is the classic chromosomal pattern for Klinefelter syndrome. - Clinical features include **hypogonadism**, **tall stature**, **gynecomastia**, and **infertility** due to the additional X chromosome. *Cri du chat syndrome* - Caused by a **deletion on chromosome 5p** (5p-), not an extra sex chromosome as shown in the mapping. - Characterized by a distinctive **cat-like cry**, **microcephaly**, and **intellectual disability**. *Eagle's syndrome* - This is **not a chromosomal abnormality** but rather an anatomical condition involving elongated **styloid process** or calcified **stylohyoid ligament**. - Presents with **throat pain**, **dysphagia**, and **otalgia**, unrelated to karyotypic changes. *Down's syndrome* - Results from **trisomy 21** (47,XX+21 or 47,XY+21), showing an extra chromosome 21, not extra sex chromosomes. - Clinical features include **intellectual disability**, **characteristic facial features**, and **cardiac defects**.

Question 1

45X0 is the chromosomal abnormality seen in which of the following conditions?

Accepted Answer

Turner's syndrome

Answer

Down's syndrome

Answer

Klinefelter's syndrome

Answer

True hermaphroditism

Question 2

Which of the following is an example of a gain-of-function mutation?

Accepted Answer

Huntington's disease

Answer

Osteogenesis imperfecta

Answer

Ehlers-Danlos syndrome

Answer

Marfan syndrome

Question 3

A pedigree chart shows the following pattern of inheritance. What is the most likely mode of inheritance?

Accepted Answer

Autosomal recessive

Answer

Autosomal dominant

Answer

X-linked recessive

Answer

X-linked dominant

Question 4

The HER2/neu receptor plays a role in what?

Accepted Answer

Predicting therapeutic response

Answer

Diagnosis of breast cancer

Answer

Screening of breast cancer

Answer

Recurrence of tumor

Question 5

Germline mutations in which of the following genes are not associated with hereditary breast cancer?

Accepted Answer

GATA2

Answer

CHEK2

Answer

BRCA2

Answer

TP53

Question 6

Which of the following chromosomes is involved in Patau syndrome?

Accepted Answer

Chromosome 13

Answer

Chromosome 18

Answer

Chromosome 21

Answer

Chromosome 5

Question 7

What is the most common tumor diagnosed in a female patient with tuberous sclerosis?

Accepted Answer

Renal Angiomyolipoma

Answer

Rhabdomyosarcoma

Answer

Pulmonary lymphangioleiomyomatosis

Answer

Optic glioma

Question 8

Beal's syndrome is caused due to a defect in which of the following genes?

Accepted Answer

Fibrillin-2

Answer

Fibrillin-1 gene

Answer

Elastin

Answer

Lamillin

Question 9

Which of the following chromosomal abnormalities is indicated by the chromosomal mapping?

Accepted Answer

Klinefelter syndrome

Answer

Cri du chat syndrome

Answer

Eagle’s syndrome

Answer

Down’s syndrome

Question 10

Hereditary retinoblastomas develop due to an abnormality in which of the following chromosomes?

Accepted Answer

13q14

Answer

13p14

Answer

14p13

Answer

14q13

Molecular Pathology — MCQs

Molecular Pathology — MCQs

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