Molecular Pathology Practice Questions

Q: Division of a chromosome perpendicular to its normal axis of division leads to which of the following?

Isochromosome. ### Explanation **Correct Option: B. Isochromosome** An **isochromosome** is a structural chromosomal abnormality formed when a chromosome divides **transversely (perpendicular)** to its longitudinal axis rather than the normal longitudinal (vertical) division. [1] * **Mechanism:** Instead of separating into two identical sister chromatids, the centromere splits horizontally. This results in one chromosome consisting of two short arms (p) and another consisting of two long arms (q). [1] * **Consequence:** The resulting cell has a loss of one arm's genetic material and a duplication of the other. The most common clinical example is **i(12p)** in germ cell tumors and **i(Xq)**, which is seen in approximately 15% of cases of **Turner Syndrome** (45,X/46,X,i(Xq)). [1] **Analysis of Incorrect Options:** * **A. Ring chromosome:** Formed when a chromosome sustains breaks at both ends (telomeres), followed by the fusion of the damaged "sticky" ends. This results in a circular structure and loss of distal genetic material. * **C & D. Acrocentric and Subtelocentric chromosomes:** These terms describe the **normal morphology** of chromosomes based on centromere position. * *Acrocentric:* Centromere is very near one end (e.g., chromosomes 13, 14, 15, 21, 22). * *Subtelocentric:* Centromere is located between the midpoint and the tip. These are not results of abnormal division. **High-Yield Clinical Pearls for NEET-PG:** * **Turner Syndrome:** The most common structural abnormality is the isochromosome of the long arm of X [i(Xq)]. [1] * **Robertsonian Translocation:** Occurs only in **acrocentric** chromosomes; it involves the fusion of two long arms and the loss of two short arms. * **Philadelphia Chromosome:** A reciprocal translocation t(9;22) seen in CML. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 169-170.

Question 1

What is the approximate resolution of visualizing chromosomes through a light microscope?

Accepted Answer

5 megabases (mb)

Answer

5 kilobases (Kb)

Answer

50 megabases (mb)

Answer

500 kilobases (Kb)

Question 2

A 45-year-old woman presents with a 2-month history of fatigue and recurrent fever. She also complains of tenderness below the right costal margin and dark urine. Physical examination reveals jaundice and mild hepatomegaly. The serum is positive for hepatitis B virus antigen. Which of the following best describes the mechanism of indirect virus-mediated hepatocyte cell death in this patient?

Accepted Answer

Immune recognition of viral antigens on the cell surface

Answer

Accumulation of abnormal cytoplasmic proteins

Answer

Generation of cytoplasmic free radicals

Answer

Impaired plasma membrane Na+/K+ ATPase activity

Question 3

Phagolysosomal-enzymatic digestion occurs due to which of the following?

Accepted Answer

Myeloperoxidase (MPO)

Answer

Protease

Answer

Oxidase

Answer

All of the above

Question 4

Karyotyping is done with all, except:

Accepted Answer

Blood monocyte

Answer

Blood lymphocyte

Answer

Amnion

Answer

Fibroblast

Question 5

Division of a chromosome perpendicular to its normal axis of division leads to which of the following?

Accepted Answer

Isochromosome

Answer

Ring chromosome

Answer

Acrocentric chromosome

Answer

Subtelocentric chromosome

Question 6

Amyloid that occurs in long-term hemodialysis is which type?

Accepted Answer

Amyloid Beta-2 microglobin

Answer

Amyloid light chain

Answer

Amyloid associated protein

Answer

Beta amyloid protein

Question 7

Which of the following tests is used to differentiate the chromosomes of normal and cancer cells?

Accepted Answer

Comparative genomic hybridization

Answer

PCR

Answer

Western Blotting

Answer

Southern Blotting

Question 8

Nonsense mutation is seen in which of the following conditions?

Accepted Answer

Thalassemia

Answer

AIHA

Answer

Sickle cell anemia

Answer

Hemophilia

Question 9

A CT scan of a 43-year-old woman with a parathyroid adenoma and hyperparathyroidism reveals extensive calcium deposits in the lungs and kidney parenchyma. These radiologic findings are best explained by which of the following mechanisms of disease?

Accepted Answer

Metastatic calcification

Answer

Arteriosclerosis

Answer

Dystrophic calcification

Answer

Granulomatous inflammation

Question 10

Klinefelter syndrome is diagnosed by which method?

Accepted Answer

Karyotyping

Answer

USG abdomen

Answer

Triple test

Answer

Echocardiography

Molecular Pathology — MCQs

Molecular Pathology — MCQs

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