What happens to a DNA molecule when a restriction enzyme is added to it, under appropriate conditions?

Restriction enzymes (RE) or restriction endonucleases are the enzymes isolated from different bacteria cells like EcoRI is obtained from the E. coli . Under appropriate conditions, they cut a dsDNA molecule at specific nucleotide sequences named recognition site (it is different for different RE). This leads to the formation of many fragments, usually four, five, or six nucleotides long. A restriction enzyme will cleave the DNA at recognition sequence results in the blunt end and sticky or staggered ends.

What are restriction enzymes?

A restriction enzyme or restriction endonucleases (REs) are enzymes that cut the dsDNA across the sugar-phosphate backbone by breaking the covalent bond holding the sugar and phosphate together. The DNA strands have specific recognition sites for REs that are usually 4 - 6 base pairs in length and are palindromic. REs (for example, EcoRI) are found in bacteria like E.coli , where they are used as a defence against bacteriophage infection by cutting their DNA inside of bacteria. Bacterial DNA is protected from restriction enzymes as their DNAs are methylated at nitrogenous bases such as adenine and cytosine.