General ---------Biology----------------------------------------------------- ------------------Online----------------------------------------------------------- Ch. 20 DNA Technology

Restriction enzymes were discovered in bacteria where they attack viral DNA and chop the DNA into
fragments.  Each different kind of restriction enzyme "recognizes" a particular base sequence, such as 
the AATGC shown below, and cuts the DNA at every point this sequence occurs.

The restriction enzyme cuts the DNA in a "dog leg" fashion.

Cut DNA has exposed bases at the ends of each fragment.  These exposed bases can hydrogen
bond to any other complimentary fragment cut with the same enzyme.  This ability to hydrogen 
bond with other cut fragments has given rise to the term "sticky ends" to describe this characteristic.
This is helpful when splicing DNA from one organism into another.

 

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