Question

Restriction Endonuclease type I is involved in:

• A. Endonuclease and Methylase
• B. Cleaving and Methylation
• C. Cut DNA within palindromic sequences
• D. Cut DNA within non-palindromic sequences

Hint:

Type II restriction enzymes are very precise, cut at or near the recognition site, and are useful for various applications in molecular biology, while type I enzymes cleave DNA at random sites and are not suitable for targeted applications.

Answer 1

The Correct Option is A

Type I restriction enzymes have both endonuclease (cleaving DNA) and methyl-transferase (modifying DNA by adding a methyl group) activities. They:
• Recognize specific DNA sequences but cleave DNA at random locations far away from the recognition site.
• Methylate specific bases within the recognition sequence to protect the host DNA from cleavage.
This dual functionality is characteristic of Type I restriction enzymes, differentiating them from other types of restriction enzymes that mainly perform cleavage. Type II enzymes cleave DNA at specific site. Type III enzymes cleave DNA at a specific sequence but not at the recognition site.