Molecular Pathology Practice Questions

Q: The DNA nick and labelling (in situ) technique is used to quantify which of the following?

The fraction of cells in the apoptotic pathway. ### Explanation The **DNA nick and labeling technique**, commonly known as **TUNEL** (Terminal deoxynucleotidyl transferase dUTP Nick End Labeling), is a gold-standard method for detecting and quantifying **apoptosis** (programmed cell death). **1. Why Option C is Correct:** A hallmark of apoptosis is the activation of endogenous endonucleases, which cleave genomic DNA into short fragments (180–200 base pairs), creating a "DNA ladder" on electrophoresis. This process leaves numerous **3'-hydroxyl (OH) ends** (nicks) in the DNA. The TUNEL assay uses the enzyme **Terminal deoxynucleotidyl transferase (TdT)** to attach labeled nucleotides (like dUTP) to these 3'-OH ends. By measuring the intensity of the label, clinicians can quantify the fraction of cells undergoing apoptosis. **2. Why Other Options are Incorrect:** * **Option A:** Mitochondrial DNA is typically quantified using qPCR or Southern Blotting, not by labeling DNA nicks. * **Option B:** Nucleic acid fractions (DNA vs. RNA) are measured using spectrophotometry (A260/A280 ratio) or specific dyes like Ethidium Bromide. * **Option C:** Meiotic division is studied via karyotyping or flow cytometry to assess DNA ploidy (n vs. 2n), not by DNA fragmentation. **3. High-Yield Clinical Pearls for NEET-PG:** * **DNA Laddering:** A classic feature of apoptosis seen on agar gel electrophoresis. In contrast, **Necrosis** shows a "smear" pattern due to random DNA degradation. * **Caspase-3:** Known as the "Executioner Caspase," it is the primary enzyme responsible for activating the endonucleases that create the nicks detected by TUNEL. * **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.

Question 1

Which of the following is a squamous cell carcinoma marker?

Accepted Answer

Cytokeratin

Answer

Vimentin

Answer

Dermin

Answer

Glial fibrillary acid protein

Question 2

Which of the following is NOT seen in Fragile X syndrome?

Accepted Answer

Genomic imprinting

Answer

Testicular enlargement

Answer

Cause of mental retardation

Answer

Trinucleotide repeat mutations

Question 3

Molecular study is important in the management of which malignancy?

Accepted Answer

Multiple myeloma

Answer

Renal cell carcinoma

Answer

Seminoma

Answer

Basal cell carcinoma

Question 4

The DNA nick and labelling (in situ) technique is used to quantify which of the following?

Accepted Answer

The fraction of cells in the apoptotic pathway

Answer

The amount of total DNA in mitochondria

Answer

The fraction of nucleic acids

Answer

The fraction of cells in meiotic division

Question 5

What is the most common microdeletion syndrome?

Accepted Answer

Velocardiofacial (VCF) syndrome

Answer

WAGR syndrome

Answer

Prader-Willi syndrome

Answer

Angelman syndrome

Question 6

Metaplasia arises from the reprogramming of which type of cell?

Accepted Answer

Stem cells

Answer

Stellate cells

Answer

Squamous cells

Answer

Columnar cells

Question 7

To which of the following does integrin bind?

Accepted Answer

Laminin

Answer

Fibronectin

Answer

Vitronectin

Answer

Collagen

Question 8

In an ablated animal, if Myeloid Stem Cells are injected, which type of cells are induced after the incubation period?

Accepted Answer

Erythroid

Answer

T-Lymphocyte

Answer

Fibroblast

Answer

Hematopoietic Stem Cells

Question 9

What is the specific chromosomal translocation associated with synovial sarcoma?

Accepted Answer

t(x;18)

Answer

t(9;22)

Answer

t(11;14)

Answer

t(14;18)

Question 10

All are present in Fragile X syndrome, except:

Accepted Answer

Mental retardation and macroorchidism

Answer

Mental retardation and microorchidism

Answer

Mental retardation and microorchidism

Answer

Microorchidism and large facies

Molecular Pathology — MCQs

Molecular Pathology — MCQs

On this page

Practice by Chapter

Want unlimited practice?