The lac operon controls the transcription of a group of genes involved in metabolizing lactose in E. coli. A group of scientists tested how to activate the lac operon. In four different mediums, they varied whether glucose or lactose was present in the medium, as indicated by a or -.The scientist discovered that the lac operon is inducible, repressed by glucose and induced by allolactose. Which medium has the right conditions to metabolize lactose

The correct answer would be - medium with lactose present and glucose absent.

Explanation:

There are genes present in lac operon that takes part in the lactose metabolism. These genes expressed only if a medium has lactose in absence of glucose.

In the absence of glucose and lactose is present, due to inducer the lac repressor is removed from the operator. This leads to the binding of CAMP to DNA as the CAMP levels are high. It helps in high transcription levels b binding RNA polymerase to promotor.