Question

Assertion (A): Restriction endonuclease recognises palindromic sequence in DNA and cuts them. Reason (R): Palindromic sequence has two unique recognition sites PstI and PvuI recognised by restriction endonuclease.

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

Hint:

Restriction endonucleases are enzymes that recognize specific palindromic sequences in DNA. Each enzyme has a distinct recognition site, and they cut the DNA at or near these sequences.

Answer 1

The Correct Option is C

Step 1: Analyzing the assertion:
- Restriction endonucleases are enzymes that cut DNA at specific sites. These enzymes typically recognize palindromic sequences, which are sequences of nucleotides that read the same forwards and backwards on complementary strands of DNA.
- The assertion is correct because restriction endonucleases do indeed recognize and cleave palindromic sequences in the DNA.
Step 2: Analyzing the reason:
- Palindromic sequences are recognized by various restriction endonucleases, but the reason given is incorrect in naming the specific recognition sites for PstI and PvuI.
- PstI recognizes the palindromic sequence 5'-CTGCAG-3', and PvuI recognizes the palindromic sequence 5'-CAGCTG-3', which are not the only recognition sites for restriction endonucleases.
- Therefore, the reason is partially incorrect because it mentions the specific sites PstI and PvuI, but these are just examples and not applicable to all restriction endonucleases.
Step 3: Conclusion:
- The assertion is correct, but the reason provided is incorrect because it gives a misleading explanation.
Thus, the correct answer is option (C): (A) is true, but (R) is false.