Exam 2: Ch 7 Control of Gene Expression in Bacteria

Question 1

in cancer, genes that restrain cell growth are ________ repressed and genes that encode proteins that promote cell growth and replication are ________ activated

Answer 1

abnormally, inapropriately

Question 2

regulation of gene expression can occur at various steps

Answer 2

transcription initiation and elongation

RNA processing

mRNA export from nucleus

translation

Question 3

control of gene expression at which two steps are most important for determining whether most genes are expressed and how much protein is produced?

Answer 3

transcription initiation and elongation

Question 4

what is pax6

Answer 4

transcription factor that regulates transcription of genes involved in eye development

Question 5

what do repressor and activator proteins do

Answer 5

recognize and bind to specific regions of DNA to control the transcription of a nearby gene

Question 6

transcription control region

Answer 6

sequences of DNA that serve as binding sites for repressor and activator proteins

Question 7

the structure and function of a cell are determined by …

Answer 7

the proteins it contains

Question 8

by controlling _____ a cell can regulate which proteins it produces, and how rapidly

Answer 8

transcription

Question 9

when transcription of a gene is ______, the corresponding mRNA and encoded protein is synthesized at low rates. Opposite of this is…

Answer 9

repressed

activated

Question 10

operons in E. coli

Answer 10

make up half the genes

encode enzymes involved in metabolic pathways or multiple proteins

Question 11

what do the lac and trp operon encode?

Answer 11

lac: 3 proteins required for metabolism of lactose
trp: 5 pp needed for biosynthesis of tryptophan

Question 12

coordinate regulation

Answer 12

all genes in an operon are activated or repressed to the same extent

Question 13

transcription of operons and isolated genes is controlled by interplay between…

Answer 13

RNA polymerase and specific repressor and activator proteins

Question 14

to initiate transcription, E. coli RNA polymerase must be associated with…

Answer 14

a sigma factor

σ70 binds RNA polymerase and to promoter DNA sequences

Question 15

σ70 is…

Answer 15

an initiation factor

Question 16

synthesis of the lac operon is repressed when….

Answer 16

there is no lactose around: to conserve energy

when there is glucose around: preferential glucose metabolism

Question 17

transcription of lac operon under different conditions is controlled by…

Answer 17

lac repressor

catabolite activator protein (CAP)

both bind to a specific DNA sequence in the lac transcription control region called the operator and CAP site

Question 18

when no lactose is present where does the lac repressor bind

Answer 18

to the lac promoter, blocking σ70 from initiating transcription

Question 19

when glucose falls, E. coli synthesizes a lot of…

Answer 19

cyclic AMP that binds to CAP protein allowing it to bind to the CAP site, stimulating rate of transcription initiation

Question 20

what makes a strong/weak promoter

Answer 20

rate of transcription

Question 21

what regulates expression of many bacterial genes via DNA-binding repressors and activators

Answer 21

small molecules

cAMP, phosphorylation

Question 22

how many σ factors are there

Answer 22

7

Question 23

enhancer

Answer 23

binding sites in DNA located 80-160bp upstream from start site

Question 24

σ54

Answer 24

sigma factor found in E. coli

binds to RNA polymerase to start transcription initiation

Question 25

NtrC protein

Answer 25

stimulates transcription of glnA gene that encodes enzyme glutamine synthetase

binds to enhancer after being phosphorylated by NrtB

Question 26

many bacterial responses are controlled by..

Answer 26

two-component regulatory systems

like NtrC and NtrB

Question 27

control of transcription elongation example

Answer 27

trp operon

Question 28

trp operon is repressed by

Answer 28

trp repressor when concentration of trp in cytoplasm is high

Question 29

when there is low concentration of tRNAtrp…

Answer 29

the ribosome stalls at the 2 Trp codons in region 1

Question 30

riboswitch

Answer 30

RNA tertiary structures that bind small molecules when present at high concentration

form hairpins that lead to early termination of transcription