Lab 7

Question 1

Why do we use IPTG instead of lactose to induce the lac operon?

Answer 1

Because in using lactose, it will eventually deplete which will turn the lac Operon off resulting in faulty results. IPTG will induce the lac Operon but is not a substrate for B-Galactidase so the lac operon will not turn off.

Question 2

How is balanced growth reached?

Answer 2

By providing the cells with a vast excess of nutrients. This way one nutrient used for growth will not be depleted.

Question 3

What happens to the generation time during exponential phase?

Answer 3

The generation time stays the same for the duration of the exponential phase because cells are being “born” and dying at the same rate

Question 4

Lag Phase

Answer 4

Time period where cells are adjusting to a new medium

Question 5

Stationary Phase

Answer 5

Depleted, the cells enter stationary phase. Stationary phase points out an important limitation in measuring the OD of a culture: the procedure does not indicate whether the cells are dead or alive, only that they are scattering light. In stationary phase, the OD can remain constant while viability decreases.

Question 6

What gene encodes the B-Galactidase?

Answer 6

LacZ

Question 7

What is the β-galactosidase role in the lac operon?

Answer 7

Breaks down lactose into glucose and galactose