Screening  a  plasmid  library  to
   recover a cloned gene.

<Li> Colonies  of  a  plasmid  library  is  overlaid with a DNA binding
filter.
<Li> Colonies  are  transferred  to  the filter, then lysed, and DNA is
denatured.
<Li> Filter   is   placed  in  a  bag  with  a  solution  containing  a
radioactively   labeled   single-stranded  DNA  probe;  the  probe
hybridizes with complementary DNA on the filter.

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