What is the protein product of the lac I gene of the lac operon?

1 Answer
Oct 2, 2016

The LacI gene codes for the repressor of the lac operon.

Explanation:

It can be somewhat confusing, but the LacI gene is not part of the Lac operon itself.

The Lac operon itself contains the genes for three enzymes:
- LacZ codes for #beta#-galactosidase
- LacY codes for #beta#-galactoside permease
- LacA codes for #beta#-galactoside transacetylase

The LacI gene is a regulatory gene that codes for the lactose-inducible lac operon transcriptional repressor. In other words, it codes for the respressor of te Lac-operon.

Home made illustration

LacI is always transcribed. When the repressor binds to the operator, the Lac genes can't be transcribed. For transcription to happen, the repressor first has to be inactivated.