Question

In lac operon model, repressor protein binds to which site?

• A. Structural genes
  
• B. Promotor
• C. Operator
• D. None of the above

Answer 1

Answer: (C)

Operator

Lac repressor is part of the regulatory network of the lac operon. Lac repressor controls the production of three proteins produced from the gene and affecting the metabolism of lactose. This repressor molecule is a tetramer whose all the subunits are identical. This tetramer binds to a particular region in the bacterial DNA called the operator. This region is present next the three lactose metabolizing proteins. Binding of the repressor to operator causes the block in the production of protein. Otherwise, for three genes to transcribe the repressor protein binds to the lactose molecule and hence unable to bind to operator allows the genes to transcribe.