Question

Assertion (A): Isoelectric focusing (IEF) is a highly sensitive analytical technique particularly useful for studying micro-heterogeneity in a protein. Reason (R): A protein may show a single band on SDS gel, but three bands on an IEF gel. The method is useful for separating isoenzymes.

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

Hint:

SDS-PAGE = Measuring by weight. IEF = Measuring by personality (Charge). Personality is more specific!

Answer 1

The Correct Option is A

Step 1: Concept
IEF separates proteins based on their isoelectric point ($pI$).

Step 2: Meaning
Micro-heterogeneity refers to small charge differences in otherwise similar proteins.

Step 3: Analysis
Assertion (A) is correct about IEF's sensitivity. Reason (R) provides the evidence: SDS-PAGE only separates by size, so similar-sized proteins appear as one band, whereas IEF catches charge differences and splits them into multiple bands.

Step 4: Conclusion
(R) is the correct explanation for (A).

Final Answer: (A)