lac operon specific

Question 1

enzymes transcribed + translated from lac operon

Answer 1

permease and beta-galactosidase

Question 2

when lactose is absent…lac operon is BLANK

Answer 2

repressed (no transcription or translation)

Question 3

explain what happens with the lac operon when lactose is absent

Answer 3

when there is no lactose in the environment, the repressor protein unbinds from the repressor gene and binds to operator. since the operator sequence is downstream of the promoter, this physically blocks RNA polymerase from transcribing. no products are produced.

Question 4

explain what happens with the lac operon when lactose is present

Answer 4

when lactose is present, it binds with the repressor protein which changes its shape (conformational change), barring the repressor from binding with the operator. nothing is blocking RNA polymerase so it can transcribe as normal. translation would then occur and the enzymes protease and beta-galactosidase are the products

Question 5

when there IS BOTH glucose and lactose what is happening with the lac operon

Answer 5

CAP (repressor protein) not bound, LAC repressor not bound, operon is OFF

no activation or repression, overall very little activity

Question 6

when there IS glucose but NO lactose, what is happening with the lac operon

Answer 6

CAP not bound, LAC repressor bound, operon is OFF

no activation but there is active represon, overall represon wins

Question 7

when there is NO glucose and NO lactose, what is happening with the lac operon

Answer 7

CAP bound, LAC repressor bound, operon is OFF

there is activation and repression, overall repression wins

Question 8

when there is NO glucose but there IS lactose, what is happening with the lac operon

Answer 8

CAP is bound, LAC repressor not bound, RNA polymerase bound, operon is ON

there is activation and no repression so transcription occurs

Question 9

what is the repressor protein used in the lac operon

Answer 9

CAP