In recombinant DNA technology, endonucleases and ligase enzymes are routinely employed. Restriction endonuclease enzymes are naturally occurring enzymes in bacteria that help protect bacteria from viral attacks by cutting up the foreign viral DNA while not harming the bacterium's own DNA. Restriction endonuclease enzymes recognize specific palindromic deoxyribonucleotide base sequences (base sequences that read the same forward and backward on the complementary DNA strands), and then split each DNA strand at a specific site within that sequence.
For example, escherichia coli makes a restriction endonuclease called eco R1 that recognizes the deoxyribonucleotide base sequence G-A-A-T-T-C and cuts the DNA strand between the G and the A. Since the complementary strand has the sequence CTTAAG, it is also cut between the G and the A. This leaves short, complementary, single-stranded sticky ends capable of hydrogen bonding with the complementary sticky ends of DNA fragments cut by the same enzyme.
Tags: Bio Technology, Bio Genetics, Artificial alteration of Genes
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