This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
What do restriction endonucleases do? 
Select and explain. 
A. Cut ds DNA at specific sites, B. Cut RNA at specific sites, C. Cut ss DNA at specific sites, D. Break peptide chains
A: Cut ds DNA at specific sites
Answer: A: Cut ds DNA at specific sites 
Explanation: Restiction Endonucleases (RE) : In order to transfer a gene, it is to be first selectively split from the parent DNA. It is usually achieved by the restriction endonucleases. RE have specific recognition sites where they cut the DNA. There are >800 such enzymes now available commercially. These enzyms recognize specific sequence with palindrome arrangement. REF :DM VASUDEVAN textbook; 8th EDITION; Page no :601