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Why are restriction enzymes referred to as scissors?

Restriction enzymes or restriction endonucleases are sometimes called scissors because they are able to cut through the sugar-phosphate backbone of double-stranded DNA. Each restriction endonuclease is able to scan a piece of DNA for a particular 4-6 base pair sequence. Every time this sequence is found, the enzyme cuts through both strands of the DNA.  This cut can be blunt or straight across both strands of DNA or it can be uneven leaving what are called sticky ends where dangling nucleotides are left on the strands.


Restriction endonucleases are important tools for producing recombinant DNA which is used frequently within the field of biotechnology. The endonucleases allow genes to be inserted into plasmids. The gene can be isolated and amplified using primers and a polymerase chain reaction and then a plasmid can be cut open using a restriction endonuclease and the gene can be inserted. Once it is inside of the plasmid, the plasmid can be put into competent bacterial cells so that they can express the gene inserted into the plasmid. Bacteria, especially E. coli, grow very rapidly to produce large populations so it is an efficient way of producing needed proteins like insulin.

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