Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: 12-20% acrylamide in PAGE restricts the migration of large molecules.
Reason R: Pore size of the gel affects the separation of molecules.

• A. Both A and R are correct and R is the correct explation of A
• B. Both A and R are correct but R is NOT the correct explation of A
• C. A is correct but R is not correct
• D. A is not correct but R is correct

Hint:

High % Acrylamide (12–20%) = Small pore size $\to$ Best for separating SMALL molecules (restricts large ones).
Low % Acrylamide (4–7.5%) = Large pore size $\to$ Best for separating LARGE molecules.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question presents an Assertion regarding acrylamide concentration effects in Polyacrylamide Gel Electrophoresis (PAGE) and a Reason regarding gel pore size influence on molecular separation.

Step 2: Key Formula or Approach:
In PAGE, acrylamide polymerizes with bis-acrylamide crosslinkers to form a three-dimensiol molecular sieve matrix.
The average gel pore size is inversely proportiol to the total concentration of acrylamide (%T). High %T acrylamide gels produce smaller pores.

Step 3: Detailed Explation:

• Alysis of Assertion A: Gels with high total acrylamide concentrations (12–20% PAGE) form dense polymer networks with small average pore diameters. These tight pores physically hinder and restrict the migration of high molecular weight (large) biomolecules, while effectively resolving small proteins or nucleic acids. Thus, Assertion A is correct.

• Alysis of Reason R: Molecular separation in gel electrophoresis relies on sieving, where the pore size of the gel dictates the retarding effect experienced by molecules according to their hydrodymic radius and size. Thus, Reason R is correct.

• Causal Relationship: Because the gel's pore size directly dictates molecular sieving (Reason R), increasing the acrylamide concentration to 12–20% reduces the pore size, which directly explains why large molecules are restricted from migrating efficiently (Assertion A). Therefore, R is the correct explation of A.

Step 4: Fil Answer:
Both A and R are correct and R is the correct explation of A.