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Biotechniques. Restriction Enzymes. Bacteria have endonucleases to cut up viral DNA. About 400 different endonucleases Each endonuclease recognises a specific sequence of about 4-6 nucleotide bases Cut DNA into fragments at these recognition sites. Specific.
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Restriction Enzymes Bacteria have endonucleases to cut up viral DNA. About 400 different endonucleases Each endonucleaserecognises a specific sequence of about 4-6 nucleotide bases Cut DNA into fragments at these recognition sites
Specific different enzymes cut the DNA at different places same enzymes always cut the DNA at the same places enzymes are named after the bacteria they are taken from
Protection against cutting Bacteria can protect their own DNA from restriction enzymes add methyl groups to A and C bases in sequences recognised by their own endonucleases
Recognition Sites cuts Genetic Engineer Toolkits • isolate specific DNA fragments • manipulate individual genes from any organism.
A A T T C G C T T A A G A A T T C A A T T C G G G G C T T A A C T T A A Sticky Ends Restriction enzyme: EcoRI Fragment A A T T C G C T T A A G Cut DNA with an overhang Only complementary sticky ends can join (same restriction enzyme)
C CC C CC G GG G GG G GG C CC G GG G GG C CC C CC DNA G GG C CC C CC G GG G GG C CC C CC G GG G GG C CC cut cut C CC G GG C CC G GG Blunt Ends can join to any other blunt end fragment - non-specific
Restriction enzymes http://videos.howstuffworks.com/hsw/22635-discoveries-with-bill-nye-restriction-enzymes-video.htm (restriction enzymes, 1 min) http://www.dnatube.com/video/1008/Tissue-Culture (restriction enzymes, 1 min) http://www.youtube.com/watch?v=aA5fyWJh5S0 (restriction enzymes, 1 min – no sound) http://www.youtube.com/watch?v=AEINuCL-5wc&feature=related (restriction enzyme, 3 min – very simple) http://www.youtube.com/watch?v=zF3REf7yKpw&feature=related (restriction enzymes, 7 min – students in lab, no sound??)