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: Assertion Evaluation:
- Restriction endonucleases are enzymes that cleave DNA at specific sites, typically recognizing palindromic sequences (nucleotide sequences that read the same forwards and backwards on complementary DNA strands).
- The assertion is accurate as restriction endonucleases indeed recognize and cleave palindromic sequences in DNA.
Step 2: Reason Evaluation:
- While palindromic sequences are recognized by various restriction endonucleases, the provided reason incorrectly specifies the recognition sites for PstI and PvuI.
- PstI recognizes the palindromic sequence 5'-CTGCAG-3', and PvuI recognizes the palindromic sequence 5'-CAGCTG-3'. These are illustrative examples and not exhaustive recognition sites for all restriction endonucleases.
- Consequently, the reason is partially incorrect due to its inclusion of specific, non-universal sites for PstI and PvuI.
Step 3: Final Determination:
- The assertion is correct, but the provided reason is flawed due to a misleading explanation.
Therefore, the appropriate conclusion is option (C): The assertion is true, but the reason is false.