Question

Study the diagram given below and answer the questions that follow.

1. Name the molecule ‘X’ synthesised by the ‘I’ gene. How does this molecule get inactivated?
2. Name the enzymes coded respectively by genes z, y, and a.
3. Which enzyme binds to the operator to initiate transcription?

Answer 1

1. X = Lac repressor protein (repressor).
   It gets inactivated when an inducer (allolactose / lactose) binds to it, changing its shape so that it cannot bind the operator.
2. z: β-galactosidase
   y: permease
   a: transacetylase
3. The repressor binds to the operator, while the RNA polymerase binds to the promoter to initiate transcription (in the presence of an inducer).