The restriction enzymes XhoI and SalI cut their specific sequences as shown below:

Xhol     5'-C             TCGAG-3'
            3'-GAGCT   C-5'
Sall      5'-G             TCGAC-3'
            3'-CAGCT   G-5'  

Can the sticky ends created by XhoI and SalI sites be ligated? If yes, can the resulting sequences be cleaved by either XhoI or SalI?

Key Concepts

Restriction Enzymes

Restriction enzymes, or restriction endonucleases, are proteins that cut DNA at specific sequences. Each enzyme recognizes a unique palindromic sequence and cleaves the DNA, resulting in either blunt or sticky ends. Understanding how these enzymes work is crucial for genetic engineering, as they allow for the precise manipulation of DNA fragments.

Sticky Ends

Sticky ends are short, single-stranded overhangs that are created when restriction enzymes cut DNA in a staggered manner. These overhangs can easily anneal with complementary sequences, facilitating the ligation of different DNA fragments. The compatibility of sticky ends is essential for successful cloning and recombinant DNA technology.

Ligation and Cleavage

Ligation is the process of joining two DNA fragments together, typically using the enzyme DNA ligase. For ligation to be successful, the sticky ends of the fragments must be complementary. After ligation, the resulting DNA can be tested for susceptibility to cleavage by the original restriction enzymes, which is important for confirming the integrity and functionality of the recombinant DNA.