E.  coli uses 3 enzymes to take up and
   metabolize the sugar lactose.
<P>
   The genes for these 3 enzymes are clustered in the lac operon.
<P>
<BR><LI> operon off
<BR><LI> operon on
<P>
   Review:  <A ClAsS=MID Href="../../../med/Vid/Johnson6e/ch13/lac_operon.swf" oNClick="popurlt('../../../../med/Vid/Johnson6e/ch13/lac_operon.swf');txtcolor('lac_operon3','gray');return false;" Id=lac_operon3><iMg sRc="/images/shockwave.gif" aLt='' boRDer=0></A>