prokaryotic gene expression

Question 1

how is prokaryotic gene expression regulated
what is the name of the enzyme?

Answer 1

simple mechanisms that control transcription by one enzyme
- RNA polymerase

Question 2

what do sigma factors recognize?
and do?

Answer 2

promoter elements (-10, -35)
load RNA polymerase at the start site

Question 3

name the enzymes in eukaryotes and describe the general transcription factors and their function in eukaryotes

Answer 3

• RNA polymerase I II III
• involved in recognizing promoter elements and assembly of pre-initiation complex, then load RNA polymerases

Question 4

Name what regulates and releases RNA polymerase

Answer 4

transcription activators and repressors

Question 5

what is the lac operon (an example of a regulated prokaryotic promoter) activated by? binds to? recruits? repressed by?

Answer 5

activator protein (CAP, Catabolite Activator Protein)
- binds to a promoter
- recruits RNA polymerase
- repressed by a repressor protein (Lac repressor)

Question 6

CONTROL IN GENE EXPRESSION IN BACTERIA
describe the level of mRNA transcription with low levels of lactose and high levels of glucose (low cAMP)

Answer 6

No mRNA transcription. the presence of lactose drives the binding of lac repressor to its binding site

Question 7

CONTROL IN GENE EXPRESSION IN BACTERIA
describe the level of mRNA transcription with high lactose and high glucose (low cAMP)

Answer 7

low transcription

Question 8

CONTROL IN GENE EXPRESSION IN BACTERIA
describe the level of mRNA transcription with high lactose and low glucose (high cAMP)

Answer 8

high transcription

Question 9

what does RNA polymerase bind to

Answer 9

-10 position relative to the transcription initiation site

Question 10

RNA polymerase requires what kind of factor to initiate transcription
what position does the sigma factor associate with

Answer 10

sigma factor
- -30 position

Question 11

in promotors, what do -10 and -30 DNA elements act as

Answer 11

basal elements

Question 12

• how does the lac repressor (lac 1) bind to DNA
• what does it prevent

Answer 12

• binds downstream of the transcription initiation site
• prevents transcription by RNA polymerase

Question 13

what is CAP activated by?
how does CAP bind to DNA
what does it stimulate

Answer 13

• activated by cAMP
• binds upstream of the transcription initiation site
• stimulates the recruitment of RNA polymerase

Question 14

what happens in the absence of glucose and presence of lactose

Answer 14

lac operon is expressed

Question 15

what is the initiation of TRP operon promoter regulated by

Answer 15

activators and repressors

Question 16

what happens if tryptophan is limiting in the cell?

Answer 16

transcription proceeds to the end of the operon
mRNA for the expression of enzymes for synthesis of tryptophan are produced

Question 17

what happens if the concentration of tryptophan is high

Answer 17

• transcription is arrested soon after initiation
• no mRNA is produced