The lac Operon

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What is an Operon?

An operon is a cluster of bacterial genes along with an adjacent promoter that controls the transcription of those genes. 

When the genes in an operon are transcribed, a single mRNA is produced for all the genes in that operon. This mRNA is said to be polycistronic because it carries the information for more than one type of protein.

What is the the lac Operon?

The lac operon is an operon required for the transport and metabolism of lactose in Escherichia coli and some other enteric bacteria.

 

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Animation is given in this site
http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter12/animation_quiz_4.html
or 
http://www.phschool.com/science/biology_place/biocoach/lacoperon/cyclic.html