Question

1. What is lactose?  
2. What codes for the production of the repressor?  
3. Why would the bacteria want to regulate the production of certain genes?  
4. When would the repressor be bound to the lac operon?  
5. What would happen if the repressor binds to the operator in the lac operon?  
6. What happens when there is lactose in the environment?  

Answer 1

a) lactose is a disaccharide of galactose and glucose. lactose is an inducer of lac operon.

b) lac I gene codes for lac repressor protein

c) genes in the lac operon codes for the enzymes required for the metabolism of lactose, cell uses lactose when other sources of energy ( glucose) is absent. glucose is the preferred energy source, and lac operon is expressed only when lactose is present because lactose induces the expression of lac operon ( lac operon is expressed at higher levels when glucose is absent and lactose is present).

d) lac repressor can bind to the operator when it is not inhibited by the inducer, that is when the inducer is absent lac repressor can bind to the lac operator.

e) lac repressor binds to the lac operator and prevents the transcription of the lac operon by preventing the movement of RNA polymerase.

f) when lactose is present, lactose prevents the binding of the lac repressor to the lac operator so RNA polymerase can transcribe lac operon, that is lac operon is expressed in the presence of lactose.