Using restriction endonucleases to isolate a gene

• Restriction endonucleases are enzymes that cut up viral DNA. They are often used by bacteria as a defence mechanism from invading pathogens.
• There are many types of restriction endonucleases. Each cuts a DNA double strand at a specific sequence of bases known as the recognition sequence.
• If a restriction endonuclease cuts between two opposite base pairs, then two straight edges (known as blunt ends) will form.
• If a restriction endonuclease doesn't cut between two opposite base pairs, it will cut DNA in a staggered way (forming sticky ends). Each strand of DNA will have exposed, unpaired bases.