1. Are genes always being transcribed and translated?

2. Gene Expression Gene expression for all genes falls into one of two categories. 1. constitutive expression – 1. known as housekeeping genes 2. induced expression –

3. lac Operon lac - lactose operon – promotergene 1gene 2gene 3 operator

4. lac Operon Bacterial cells mainly use glucose as a source of energy. The lac operon is only turned (on or off?) when glucose is absent, but lactose is present.

5. lac Operon Operon codes for three enzymes   -galactosidase (lacZ gene) 2. permease (lacY gene) 3. transacetylase (lacA gene)

6. lac Operon The lacI gene codes for a separate repressor protein.

7. lac Operon repressor protein (lacI gene) binds to the prevents RNA polymerase from When do you want the repressor to bind / not bind to the operon?

8. When lactose is absent:

9. When lactose is present:

10. lac Operon effector molecule – inducer –

12. lac Operon Animation lac Operon Animation