Prokaryotic Transcriptional Regulation

Question 1

Cues

Answer 1

proteins are produced in response to environmental cues

Question 2

Lactose Permease

Answer 2

transport protein that allows for the transport of lactose into the cells

Question 3

Repressor

Answer 3

• made our of 4 subunits that are able to twist the lac operon DNA in a loop, making the RNA polymerase unable to bind to it
• can be allosterically inhibited

Question 4

Operons

Answer 4

groups of related genes with similar functions can often be found clustered together

Question 5

Operon Model

Answer 5

• groups of functionally related genes are organized into transcriptional units along the bacterial chromosome
• controlled by a single on off switch that can control transcription of a clustered gene
• coordination is mediated by an operon which consists of a promoter, operator, and the coordinated gene cluster whose products will function as a common pathway

Question 6

Operator

Answer 6

sequence of nucleotides near the start of the operon that can be regulated to allow or inhibit transcription

Question 7

What happens when the operator is not bound to any inhibitor?

Answer 7

RNA polymerase can bind to the promoter and transcribe genes resulting in polycistronic mRNA which code for multiple proteins

Question 8

Lac Y

Answer 8

gene codes for lactose permease which will embed itself in the cell membrane and allow for the import of lactose into the bacterial cell

Question 9

Lac Z

Answer 9

codes for B-galactosidase that splits lactose into glucose and galactose

Question 10

Lac I

Answer 10

codes for repressor protein which can bind to the operator and inhibit transcription
-controls expression of lacY and lacZ

Question 11

Negative Regulation

Answer 11

• ability of the repressor protein to halt transcription
• accomplished because repressor protein is constitutively expressed at low levels
• repressor protein binds to lac O causing RNA polymerase to not bind to the promoter

Question 12

High glucose Levels

Answer 12

-inhibition of adenylyl cyclase which catalyzes cAMP resulting in low cAMP levels

Question 13

Low glucose levels

Answer 13

-increase activity of adenylyl cyclase producing high cAMP levels

Question 14

Why the amount of cAMP is important for regulation?

Answer 14

-determines whether an activator will bind to the site or not, deciding the degree of positive regulation

Question 15

What do low levels of glucose signal cAMP to do?

Answer 15

-to activate the positive regulator (CRP) and the presence of lactose binds the repressor protein to allow transcription of the operon to occur

Question 16

______________ binds to an activator site on the DNA allowing _________ to bind to the promoter to initiate transcription

Answer 16

Transcriptional activator protein

RNA polymerase