Question

Given below are two statements:
Statement I: Restriction endonucleases recognise specific sequences to cut DNA known as palindromic nucleotide sequences.
Statement II: Restriction endonucleases cut the DNA strand a little away from the centre of the palindromic site.
In the light of the above statements, choose the most appropriate answer from the options given below: 

• A. Both statement I and Statement II are correct
• B. Both statement I and Statement II are incorrect
• C. Statement I is correct but statement II is incorrect
• D. Statement I is incorrect but statement II is correct

Answer 1

The Correct Option is A

To solve the problem, let's evaluate the given statements:

Statement I: Restriction endonucleases recognise specific sequences to cut DNA known as palindromic nucleotide sequences.

Explanation: Restriction endonucleases are enzymes that cut DNA at specific sequences. These specific sequences are often palindromic, meaning they read the same forwards and backwards on complementary strands. This statement is correct.

Statement II: Restriction endonucleases cut the DNA strand a little away from the centre of the palindromic site.

Explanation: When restriction endonucleases cut DNA, they often make staggered cuts near or at the palindromic site, not necessarily right at the center. This creates 'sticky ends' or 'blunt ends', which are crucial for DNA recombination techniques. Hence, this statement is also correct.

Considering the explanations, the most appropriate answer from the given options is: Both statement I and Statement II are correct.

Answer 2

Let's consider both statements one by one:

Statement I: Restriction endonucleases recognise specific sequences to cut DNA known as palindromic nucleotide sequences.

This statement is correct. Restriction endonucleases are enzymes that cut DNA at or near specific recognition nucleotide sequences known as restriction sites. These sites are typically palindromic sequences, meaning they read the same forward and backward on complementary strands.

Statement II: Restriction endonucleases cut the DNA strand a little away from the centre of the palindromic site.

This statement is also correct. While some restriction enzymes cleave at the exact site of the recognition sequence, others, known as those that produce sticky ends, cut asymmetrically away from the center, which usually results in a staggered cut with overhanging sequences. This property is utilized in molecular cloning and genetic engineering to facilitate the joining of DNA fragments.

Based on the correctness of both statements, the most appropriate answer is:

Both statement I and Statement II are correct