Question

Agarose gel electrophoresis is used to separate DNA fragments. The DNA fragments separate due to \rule{2cm{0.15mm} .}

• A. difference in their staining property
• B. difference in the base sequence in them
• C. positive charge on the fragments
• D. difference in the size of fragments

Hint:

Rule: Smaller DNA fragments $\rightarrow$ move faster $\rightarrow$ travel farther in gel.

Answer 1

The Correct Option is D

Concept: Agarose gel electrophoresis is a technique used to separate DNA fragments based on their physical properties.
• DNA molecules are negatively charged due to phosphate groups.
• When an electric field is applied, DNA moves toward the positive electrode (anode).
• The agarose gel acts as a molecular sieve.

Step 1: Understand the principle of separation.
DNA fragments move through the pores of the gel. Smaller fragments move faster and travel farther than larger ones.

Step 2: Analyze the role of size.
Since all DNA fragments have similar charge-to-mass ratio, separation primarily depends on their size.

Step 3: Evaluate options.
• (A) Staining property: Used for visualization, not separation
• (B) Base sequence: Does not affect migration significantly
• (C) Positive charge: Incorrect, DNA is negatively charged
• (D) Size difference: Correct

Step 4: Conclusion.
Thus, DNA fragments are separated based on their size. Final Answer: Option (D)