Question

Two dimensional gels are mostly used to

• A. Separate DNA fragments
• B. Separate RNA fragments
• C. Separate DNA from RNA fragments
• D. Separate different proteins

Hint:

Remember the two coordinates:
X-axis = Charge (pI).
Y-axis = Size (Mass).
This is the fundamental tool for studying differential protein expression under stress or disease conditions.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks for the primary application of 2D gel electrophoresis (2D-PAGE), which is a high-resolution analytical technique in molecular biology.
Detailed Explanation:

• Concept of 2D Electrophoresis:
Unlike standard 1D gels that separate molecules by only one property, 2D gels separate molecules in two stages based on two different physical properties.

• Mechanism in Proteomics:
First Dimension: Proteins are separated by their isoelectric point (pI) using a technique called Isoelectric Focusing (IEF). Proteins move in a pH gradient until they reach the pH where their net charge is zero.
Second Dimension: The IEF strip is placed on an SDS-PAGE gel, and proteins are separated perpendicularly based on their molecular weight (MW).

• Why use it?
Proteomes (the entire set of proteins in a cell) are extremely complex.
A 1D gel might show a single thick band containing multiple different proteins of the same size.
A 2D gel resolves these into distinct "spots," allowing for the identification and quantification of thousands of individual proteins.

Step 2: Final Answer:
Two-dimensional gels are primarily used in proteomics to separate and analyze complex mixtures of different proteins.