AIIMS CRE, SNO-2024: Which system is used for DNA visualization after electrophoresis?

AIIMS CRE, SNO-2024

Pathology & Genetics

Easy

Appeared in: AIIMS CRE, SNO-2024

Explanation

A gel documentation system is specifically designed to visualize and capture images of DNA separated by gel electrophoresis.
It works on the principle of fluorescence, where a UV or LED light source excites a fluorescent dye that has been bound to the DNA fragments in the gel.
The emitted light from the dye makes the DNA bands visible, and a built-in camera records the image for analysis of fragment size and quantity.
This allows for the confirmation of PCR products, analysis of restriction digests, and other molecular biology applications.

Option A: A microscope is used to magnify and observe microscopic objects like cells or bacteria. The bands of DNA in an electrophoresis gel are macroscopic and do not require microscopic magnification for visualization.
Option C: A spectrophotometer measures the concentration and purity of a substance in a solution by analyzing its light absorbance at specific wavelengths (e.g., 260 nm for DNA). It provides a quantitative value, not a visual image of separated DNA bands in a gel.
Option D: A pH meter is an instrument used to measure the acidity or alkalinity (pH) of a liquid. It has no role in the visualization of DNA.

Visual 1: Image - A gel documentation system. The image should show the main components: a dark hood, a UV transilluminator base where the gel is placed, and a screen displaying the captured image of glowing DNA bands.
Visual 2: Flowchart - The workflow of DNA analysis. It should show the steps: 1. DNA Extraction -> 2. PCR Amplification -> 3. Gel Electrophoresis -> 4. Staining -> 5. Visualization with a Gel Documentation System.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Laboratory instrumentation for molecular biology techniques as background academic context rather than a clinical decision trigger.
Gel electrophoresis and visualization are cornerstone techniques in clinical diagnostics for genetic testing (e.g., identifying gene mutations for diseases like sickle cell anemia or cystic fibrosis), paternity testing, and forensic analysis.
Nurses working in specialized areas like genetic counseling, oncology, or clinical research may be involved in collecting patient samples (e.g., blood, saliva) for DNA analysis and need to understand the principles to help interpret results or explain the process to patients and their families.
What if? If the question asked for a tool to quantify the total concentration of DNA in a liquid sample before separation, the correct answer would be the Spectrophotometer.

How to Approach the Question

First, identify the key parts of the question: the task is 'DNA visualization' and the context is 'after electrophoresis'.
Think about the electrophoresis process: DNA is separated in a gel, but it's invisible. To see it, it needs to be stained with something that glows under a specific light.
Evaluate each option based on this requirement:
A microscope is for viewing very small things, not bands in a gel.
A spectrophotometer measures concentration by light absorption, it doesn't create an image of bands.
A pH meter measures acidity, which is irrelevant for visualization.

Concept Tested & Keywords

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E6 Pathology- ROBBINS & COTRAN PATHOLOGIC BASIS OF DISEASE 10TH Ed p. 115-118