(A) : In electric field, an amino acid migrate towards cathode when `pH gt pI`
(R ) : When pH is greater than PI anionic form of amino acid predominates.

Options

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

Answer

To solve the question, we need to analyze the statements (A) and (R) regarding the behavior of amino acids in an electric field in relation to their isoelectric point (pI) and pH.

### Step-by-Step Solution:

1. **Understanding pI and pH**:
- The isoelectric point (pI) of an amino acid is the pH at which the amino acid has no net charge. At this point, the positive and negative charges balance each other out.

2. **Behavior of Amino Acids in Electric Fields**:
- In an electric field, charged particles migrate towards electrodes. Cations (positively charged) move towards the cathode (negative electrode), while anions (negatively charged) move towards the anode (positive electrode).

3. **Analyzing Statement (A)**:
- The statement (A) claims that an amino acid migrates towards the cathode when pH > pI.
- When pH is greater than pI, the amino acid predominantly exists in its anionic form (negatively charged), which means it would actually migrate towards the anode, not the cathode. Therefore, statement (A) is **false**.

4. **Analyzing Statement (R)**:
- The statement (R) claims that when pH is greater than pI, the anionic form of the amino acid predominates.
- This is true because, at pH levels above the pI, the amino acid loses protons and carries a negative charge. Thus, statement (R) is **true**.

5. **Conclusion**:
- Since (A) is false and (R) is true, the correct answer is that (A) is incorrect while (R) is correct.

### Final Answer:
- (A) is false, and (R) is true.