Molecular Pathology Practice Questions

Q: What is the CD marker for histiocytosis?

CD 1a. **Langerhans Cell Histiocytosis (LCH)** is a proliferative disorder of Langerhans cells, which are specialized dendritic cells [1]. In pathology, identifying these cells requires specific immunohistochemical (IHC) markers. **Why CD1a is the correct answer:** CD1a is the most specific and widely used diagnostic marker for Langerhans cells. It is a protein involved in presenting lipid antigens to T-cells. In the context of LCH, the presence of **CD1a** and **S100** on IHC, along with the identification of **Birbeck granules** (tennis-racket shaped organelles) on electron microscopy, confirms the diagnosis [1]. **Analysis of incorrect options:** * **CD1b, CD1c, and CD1d:** While these are also members of the CD1 family involved in lipid antigen presentation, they are not used as diagnostic markers for histiocytosis. CD1b and CD1c are expressed on various subsets of dendritic cells and B-cells, while CD1d is primarily involved in presenting lipids to NKT cells. They lack the diagnostic specificity required for LCH. **High-Yield Clinical Pearls for NEET-PG:** * **Langerin (CD207):** This is the most specific marker for LCH as it is directly associated with the formation of Birbeck granules [1]. * **BRAF V600E Mutation:** Found in approximately 50% of LCH cases; it is a common "hot topic" in molecular pathology [1]. * **Classic Triad (Hand-Schüller-Christian disease):** Calvarial bone defects, diabetes insipidus, and exophthalmos. * **Letterer-Siwe Disease:** The aggressive, multisystem form of LCH seen in infants (<2 years). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 629-630.

Q: Which of the following is an execution caspase?

Caspase 3. Apoptosis (programmed cell death) is mediated by a family of cysteine proteases called **Caspases** [1]. These are broadly categorized into **Initiator caspases** and **Executioner (Effector) caspases**. **1. Why Caspase 3 is Correct:** Caspase 3 is the primary **Executioner Caspase**. Once activated by initiator caspases, executioners (Caspases 3, 6, and 7) cleave structural proteins and activate nucleases (like CAD - Caspase Activated DNase), leading to the characteristic morphological changes of apoptosis, such as DNA fragmentation and cell shrinkage. **2. Analysis of Incorrect Options:** * **Caspase 8:** This is an **Initiator Caspase** for the **Extrinsic (Death Receptor) Pathway** [1]. It is activated by the binding of ligands like FasL to the Fas receptor. * **Caspase 9:** This is an **Initiator Caspase** for the **Intrinsic (Mitochondrial) Pathway** [1]. It is activated when Cytochrome C is released into the cytosol and forms the "Apoptosome" complex. * **Caspase 5:** This belongs to the **Inflammatory Caspase** group (along with Caspases 1, 4, and 11), which are involved in pyroptosis and cytokine processing rather than the standard apoptotic cascade [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Initiator Caspases:** 8, 9, 10. * **Executioner Caspases:** 3, 6, 7. * **Intrinsic Pathway Marker:** Cytochrome C release from mitochondria [1]. * **Extrinsic Pathway Marker:** Activation of Caspase 8 (which can also cross-talk with the intrinsic pathway via the protein **Bid**). * **DNA Laddering:** A hallmark of apoptosis caused by internucleosomal cleavage of DNA by Caspase-activated nucleases. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 64-69.

Question 1

Which one of the following is an antiapoptotic protein or gene?

Accepted Answer

BCL-2

Answer

BAK

Answer

BAX

Answer

BIM

Question 2

All of the following are chromosomal breakage syndromes except?

Accepted Answer

Ehlers-Danlos syndrome

Answer

Fanconi's anaemia

Answer

Bloom syndrome

Answer

Ataxia telangiectasia

Question 3

Inheritance pattern of Familial Hypercholesterolemia is:

Accepted Answer

Autosomal dominant

Answer

Autosomal recessive

Answer

X-linked dominant

Answer

X-linked recessive

Question 4

What is the CD marker for histiocytosis?

Accepted Answer

CD 1a

Answer

CD 1b

Answer

CD 1c

Answer

CD 1d

Question 5

All are factors of poor wound healing EXCEPT?

Accepted Answer

Young age

Answer

Infection

Answer

Zinc deficiency

Answer

Vitamin D deficiency

Question 6

Deletion of chromosome 11 is associated with which of the following conditions?

Accepted Answer

Wilms tumor

Answer

Neuroblastoma

Answer

Retinoblastoma

Answer

Osteosarcoma

Question 7

A normal parent has two siblings with osteogenesis imperfecta. What is the most likely pattern of inheritance?

Accepted Answer

Germline mosaicism

Answer

Mutation

Answer

Anticipation

Answer

Genomic imprinting

Question 8

A tissue preparation is experimentally subjected to a hypoxic environment. The cells in this tissue begin to swell, and chromatin begins to clump in cell nuclei. ATPases are activated, and ATP production decreases. Which of the following ions accumulating in mitochondria and the cytosol contributes most to these findings and to eventual cell death?

Accepted Answer

Ca2+

Answer

Cl-

Answer

HCO3-

Answer

K+

Question 9

Which of the following is an execution caspase?

Accepted Answer

Caspase 3

Answer

Caspase 5

Answer

Caspase 8

Answer

Caspase 9

Question 10

BRAF V600E mutations are seen in all of the following except?

Accepted Answer

Grade II astrocytoma

Answer

Langerhans cell histiocytosis

Answer

Erdheim Chester disease

Answer

Ovarian carcinoma

Molecular Pathology — MCQs

Molecular Pathology — MCQs

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