What is the significance of restriction enzymes?

Restriction enzymes are proteins that cleave DNA at specific sites, known as restriction sites. They are found in bacterial cells, where they cleave foreign DNA, thus defending against infecting bacterial viruses or bacteriophages. 

The significance of restriction enzymes is that they prevent the replication of bacteriophage DNA by cleaving it into multiple pieces. Restriction enzymes can be isolated from bacterial cells and used in the laboratory as indispensable tools in genetic engineering or recombinant DNA technology.