exam 3 part 1

Question 1

-three genes are involved: Lac ___, Lac ___ and Lac A___. In addition to these three genes, the operon contain control region that regulate the expression. These include the core promoter region, the operator and the CAP binding site

Answer 1

-three genes are involved: Lac Z, Lac Y, and Lac A. In addition to these three genes, the operon contain control region that regulate the expression. These include the core promoter region, the operator and the CAP binding site

Question 2

Strong transcription of the lac operon occurs. The lac repressor is released from the operator. ____ levels are high because glucose is absent, so ____ is active and bound to the DNA. ____ helps RNA polymerase bind to the promoter, permitting high levels of transcription.

Answer 2

Strong transcription of the lac operon occurs. The lac repressor is released from the operator because the inducer (allolactose) is present. cAMP levels are high because glucose is absent, so CAP is active and bound to the DNA. CAP helps RNA polymerase bind to the promoter, permitting high levels of transcription.

Question 3

____produce protein (repressor) that always binds to the operator, prevents initiation of transcription by RNA pol

when the lactose is present, the ____ “leaks” in to the cell, the tetramer to the repressor protein and change its conformational shape and the repressor is off.

“_____” expressed

As soon as the transcription finish, _____ binds back to the operator

Answer 3

LAC I produce protein (repressor) that always binds to the operator, prevents initiation of transcription by RNA pol
when the lactose is present, “leaks” in to the cell, the tetramer bind to the repressor protein and change its conformational shape and the repressor is off.

“constitutively” expressed

As soon as the transcription finish, repressor binds back the operator

Question 4

______ alone does not bind very well to the lac operon promoter. It needs help to _____ activator protein(____, the protein that binds ____ sequence, ____ sequence), helps sigma bind at core promoter. Without help, the gene transcribe in a little amount

Answer 4

RNA polymerase alone does not bind very well to the lac operon promoter. It needs help to catabolite activator protein(CAP, the protein that binds CAP sequence,CIS sequence), helps sigma bind at core promoter. Without help, the gene transcribe in a little amount

Question 5

Cap isn’t always active, it is regulated by _____. ___ is made by E.coli when glucose levels are low. ___ binds to ___, changing its shape and making it able to bind DNA and promote transcription. Without ___, ____ cannot binds _____ and is inactive

Answer 5

Cap isn’t always active, it is regulated by cAMP. cAMP is made by E.coli when glucose levels are low. cAMP binds to CAP, changing its shape and making it able to bind DNA and promote transcription. Without cAMP, CAP cannot binds DNA and is inactive

Question 6

The lac operon of E. coli contains genes involved in lactose metabolism. It’s expressed only when ___ is present and ____ is absent.

Answer 6

The lac operon of E. coli contains genes involved in lactose metabolism. It’s expressed only when lactose is present and glucose is absent.

Question 7

Two regulators turn the operon “on” and “off” in response to lactose and glucose levels: the____ and catabolite activator protein (____).

Answer 7

Two regulators turn the operon “on” and “off” in response to lactose and glucose levels: the lac repressor and catabolite activator protein (CAP).

Question 8

__________-acts as a glucose sensor. It activates transcription of the operon
______ acts as a lactose sensor. It normally blocks transcription of the operon

Answer 8

Catabolite activator protein (CAP) acts as a glucose sensor. It activates transcription of the operon
The lac repressor acts as a lactose sensor. It normally blocks transcription of the operon

Question 9

GAL 4 is ____ sensitive, genes that turn ___ in presence of ___

Answer 9

GAL 4 is Galactose sensitive, genes that turn on in presence of galactose

Question 10

bacterial polymerase
α (2): ______ assembly and catalysis
β: ______: chain initiation and elongation
β’: _______ to DNA template
(______): ‘sticks’ enzyme subunits together?

sigma:
_____ factor, attach to the core promoter

Answer 10

bacterial polymerase
α (2): Enzyme assembly and catalysis
β: Catalysis: chain initiation and elongation
β’: Binds to DNA template
(omega): ‘sticks’ enzyme subunits together?

sigma:
initiation factor, attach to the core promoter

Question 11

sigma:

• generally -___ —- -___ region, rich in __ and ___
• bacterial species ____ significantly in the number of sigma factors, reflecting the different environmental conditions
• variation in both promoter element spacing and sequence allow different regulation of genes

Answer 11

sigma:

• generally -35 —- -10 region, rich in A and T
• bacterial species differ significantly in the number of sigma factors, reflecting the different environmental conditions
• variation in both promoter element spacing and sequence allow different regulation of genes

Question 12

GAL___-______ sensitive, genes that turn ___ in presence of galactose

Answer 12

GAL4-Galactose sensitive, genes that turn on in presence of galactose

Question 13

GAL ____is a ______ element that bind to the upstream actibatiating sequence, when _____ is not present, a protein called GAL ______ binds to its activation domain, when galactose is present, a protein called GAL_____ binds to GAL_____, prevent GAL ___ block the GAL___. Therefore, GAL ____Is exposed and help to bond ____ and mediator

Answer 13

GAL 4 is a trans element that bind to the upstream actibatiating sequence, when galactose is not present, a protein called GAL 80 binds to its activation domain, when galactose is present, a protein called GAL3 binds to GAL80, prevent GAL 80 block the GAL4. Therefore, GAL 4 Is exposed and help to bond SAGA and mediator