CH 461 Lecture Notes - Lecture 37: Restriction Enzyme, Ecori, Phosphodiester Bond
Document Summary
Restriction enzymes function like a primitive immune system. Bacteria use these enzymes to cut dna from foreign sources, like the viruses that infect them (called bacteriophage). The cut dna can"t be used to make new bacteriophage, so while the virus may kill one bacterial cell, the culture of bacteria as a whole will be spared. Bacteria refrain from cutting their own dna by modifying it, usually by methylating it, so that it is not a substrate for the restriction enzymes. The most useful enzymes are the so called type ii restriction enzymes that cut double stranded dna at short palindromic the two pieces of dna separate, the 5 paatt portion of each piece is single stranded. Other type ii restriction sequences ( palindromes are sequences that read the same in the 5 to 3 direction). For example, the enzyme ecori (from certain strains of the bacterium e. coli) cleaves.
