General Pathology Practice Questions

Q: Which of the following is the most common fixative used in electron microscopy?

Glutaraldehyde. **Explanation:** **1. Why Glutaraldehyde is the Correct Answer:** Glutaraldehyde is the gold standard fixative for **Electron Microscopy (EM)** because it is a dialdehyde that forms extensive cross-links between proteins. This rapid and stable cross-linking preserves the **ultrastructural details** of organelles (like mitochondria and endoplasmic reticulum) with high fidelity. For EM, tissues are typically "double-fixed": first with **Glutaraldehyde** (to preserve morphology) and subsequently with **Osmium Tetroxide** (to preserve lipids and provide electron density/contrast). **2. Analysis of Incorrect Options:** * **Formalin (10% Neutral Buffered Formalin):** This is the most common fixative for **Light Microscopy**. While it preserves general tissue architecture well, it does not preserve ultrastructural details sufficiently for the high magnification of EM. * **Picric Acid:** A component of **Bouin’s solution**, it is excellent for preserving glycogen and delicate tissues (like testes or GI biopsies) but causes significant shrinkage, making it unsuitable for EM. * **Absolute Alcohol:** This is a **dehydrating/precipitating fixative**. It is primarily used for cytological smears or when preserving pigments and enzymes, but it causes severe tissue distortion and is never used for EM. **3. High-Yield Clinical Pearls for NEET-PG:** * **Best Fixative for EM:** Glutaraldehyde (followed by Osmium Tetroxide). * **Best Fixative for Light Microscopy:** 10% Neutral Buffered Formalin. * **Best Fixative for Renal Biopsy (Immunofluorescence):** Michel’s medium (transport medium). * **Best Fixative for Lipids:** Osmium Tetroxide. * **Fixative for Gout (Urate crystals):** Absolute Alcohol (as water-based fixatives dissolve the crystals).

Q: In-situ DNA nick end labeling can quantitate what fraction of cells?

Cells in apoptotic pathways. **Explanation:** **TUNEL (Terminal deoxynucleotidyl transferase dUTP Nick End Labeling)** is a specialized laboratory technique used to detect and quantitate cells undergoing **apoptosis**. **Why Option A is Correct:** A hallmark of apoptosis is the activation of endogenous endonucleases (caspase-activated DNase), which cleave genomic DNA into fragments of 180–200 base pairs (creating the characteristic "DNA laddering" on electrophoresis). These breaks result in numerous exposed **3'-hydroxyl (3'-OH) ends** or "nicks." The TUNEL assay uses the enzyme **Terminal deoxynucleotidyl transferase (TdT)** to attach labeled nucleotides (like dUTP) to these 3'-OH ends. The intensity of the labeling is proportional to the degree of DNA fragmentation, allowing for the quantification of apoptotic cells. **Why Other Options are Incorrect:** * **Option B (Cells in S phase):** These are typically identified using **BrdU (Bromodeoxyuridine)** labeling or Ki-67 protein expression, which mark DNA synthesis and active proliferation. * **Option C (p53 gene product):** p53 is a tumor suppressor protein detected via **Immunohistochemistry (IHC)**. While p53 can trigger apoptosis, TUNEL measures the resulting DNA damage, not the protein itself. * **Option D (bcr/abl gene):** This fusion gene (Philadelphia chromosome) is detected using **FISH (Fluorescence In Situ Hybridization)** or **RT-PCR**, not by end-labeling DNA nicks. **High-Yield Clinical Pearls for NEET-PG:** * **DNA Laddering:** A specific feature of apoptosis (not necrosis) seen on agar gel electrophoresis. * **Annexin V:** Another marker for apoptosis; it binds to **Phosphatidylserine**, which flips from the inner to the outer leaflet of the plasma membrane during early apoptosis. * **Caspase-3:** The most common "executioner" caspase involved in both intrinsic and extrinsic pathways.

Question 1

All of the following are types of genetic polymorphism, except?

Accepted Answer

Pleiotropism

Answer

Copy number variation

Answer

Single nucleotide polymorphisms

Answer

None of the above

Question 2

Which of the following is the most common fixative used in electron microscopy?

Accepted Answer

Glutaraldehyde

Answer

Formalin

Answer

Picric acid

Answer

Absolute alcohol

Question 3

What does not occur in lysosomal storage disorders?

Accepted Answer

Lysis of the cell

Answer

Increased number and size of lysosomes

Answer

Apoptosis of the cell

Answer

Accumulation of polyubiquitinated proteins

Question 4

Provisional matrix is made up of?

Accepted Answer

All of the above

Answer

Fibrin

Answer

Fibronectin

Answer

Fibrinogen

Question 5

The recurrence of pleomorphic adenoma is attributed to which of the following factors?

Accepted Answer

Presence of an incomplete capsule

Answer

Mixed origin

Answer

Absence of capsule

Answer

Perineural spread

Question 6

In-situ DNA nick end labeling can quantitate what fraction of cells?

Accepted Answer

Cells in apoptotic pathways

Answer

Cells in S phase

Answer

p53 gene product

Answer

bcr/abl gene

Question 7

Which of the following statements is NOT true about cutaneous calciphylaxis?

Accepted Answer

It exemplifies dystrophic calcification.

Answer

It is a potentially lethal condition.

Answer

It is characterized by progressive cutaneous vascular calcification.

Answer

It is seen in patients with chronic renal failure who have increased calcium, phosphate, and parathormone levels.

Question 8

A pregnant uterus is an example of which of the following cellular adaptations?

Accepted Answer

Hypertrophy

Answer

Metaplasia

Answer

Dysplasia

Answer

Atrophy

Question 9

Which of the following is NOT an antigen-presenting cell?

Accepted Answer

T-cells

Answer

Langerhans cell

Answer

Dendritic cells

Answer

B-cells

Question 10

What type of necrosis is typically seen in nervous tissue?

Accepted Answer

Liquefactive

Answer

Coagulative

Answer

Caseous

Answer

Fibrinoid

General Pathology — MCQs

General Pathology — MCQs

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