Question

 

1. Describe with detail how this molecular switch is analogous to a light switch that one person turns on and another person turns off. In your description indicate the molecular components in “turning on” and “turning off” the switch.

2. Describe why it is just as important for normal cell functioning to turn the switch off as it is to turn the switch on.

Answer 1

The presence and absence of any molecule result in the switching ON and OFF of the genes which can be correlated to the person turning ON and OFF of the switch. Negative repressor example - the absence of lactose, the lac Repressor protein, encoded by the lacI gene with a separate promoter that is always active, binds to the Operator sequence in the DNA. The Operator sequence is a type of DNA regulatory element. Repressor protein bound to the Operator prevents RNA polymerase from initiating transcription.

Positive regulation example-Glucose is the preferred substrate for energy metabolism. When glucose is present, cells transcribe the lac operon only at very low levels, so the cells obtain most of their energy from glucose metabolism.

Each cell expresses only a fraction of its genes it is switching ON those genes. The rest of the genes are repressed, or turned off. The process of turning genes on and off is known as gene regulation. Gene regulation is an important part of normal development. Genes are turned on and off in different patterns during development. Gene regulation also allows cells to react quickly to changes in their environments.