Gene Regulation in Bacteria

Question 1

promoter region

Answer 1

where RNA polymerase binds

Question 2

operon

Answer 2

functioning unit of genomic DNA containing a cluster of separate coding sequences under control of a single operon

Question 3

trp operon is _

Answer 3

repressible; bacteria synthesizes its own tryptophan unless tryptophan becomes available

Question 4

trpR repressor protein

Answer 4

sensory for trp level; can not bind DNA (operator) without tryptophan

Question 5

tryptophan in trpR repressor

Answer 5

acts as a co-repressor

Question 6

trpR binding the operator prevents _

Answer 6

RNA polymerase binding

Question 7

operator

Answer 7

the piece of DNA that the repressor binds to

Question 8

attenuation

Answer 8

regulation of transcription after the initiation step, causing premature termination of transcription

Question 9

translation of _ controls transcription in the trp operon

Answer 9

leader sequence

Question 10

leader sequence

Answer 10

region 3 can base pair with region 2 to allow continuation of transcription or region 4 to termination transcription

Question 11

if the leader sequence is completely translated _

Answer 11

region 3 will base pair with region 4 and repress the trp operon (tryptophan is present)

Question 12

control sites of the trp operon

Answer 12

operator and leader

Question 13

What would happen if codons coding for histidine in the leader sequence were removed?

Answer 13

wouldn’t pass region 1, so 3 will base pair with 4 leading to termination

Question 14

no glucose but lactose available

Answer 14

lac genes are expressed

Question 15

high glucose but no lactose

Answer 15

lac operon is off (usual)

Question 16

both lactose and glucose available

Answer 16

low transcription of lac operon, glucose used first

Question 17

lac operon is _

Answer 17

inducible; usually off because glucose is present for metabolism

Question 18

lac operon pathway

Answer 18

no glucose but high lactose leads to production of cAMP –> cAMP binds CAP –> CAP helps RNA polymerase bind promoter –> lac operon is transcribed

Question 19

regulated genes

Answer 19

expressed only under certain conditions; usually to control cell growth and division as needed by cell

Question 20

constitutive genes

Answer 20

continuously expressed (housekeeping genes required for protein synthesis)

Question 21

lacZ

Answer 21

beta-galactosidase; enzyme that breaks lactose into 2 monosaccharides

Question 22

lacY

Answer 22

transporter

Question 23

lacI

Answer 23

produces a repressor that inhibits lacZ, lacY, and lacA; binding of lactose (or IPTG) inactivates it

Question 24

lacI is _

Answer 24

constitutively expressed

Question 25

mutations that knock out lacI (lacI-)

Answer 25

constitutive expression of lacZ, lacY, and lacA

Question 26

cis-elements

Answer 26

DNA sequence (operator) that influences expression of genes only on the same chromosome

Question 27

trans-factors

Answer 27

proteins or RNAs, such as lac repressor, that can diffuse and act on different molecules

Question 28

cis-regulation

Answer 28

regulator resides on the same molecule as the target; operator and promoter (DNA sequences)

Question 29

trans-regulation

Answer 29

regulator can be provided by a different molecule; protein or RNAs