Regulation of Gene Expression in Bacteria

Question 1

Genes that are always active because their function is always needed- “housekeeping genes”

(Ex: genes that encode for glucose metabolism)

Answer 1

Constitutive Genes

Question 2

Gene activity is induced or repressed in response to the needs of the cell or organism

(genes that encode for lactose metabolism)

Answer 2

Regulated genes

Question 3

Genomic unit characterized by a cluster of genes under the control of a common promoter that are transcribed together

Answer 3

Operon

Question 4

Bound by transcriptional repressors to inhibit transcription, or sequences bound by transcriptional activators to increase transcription

Answer 4

Operators

Question 5

Activators bind to activator binding sites (sequence specific) to assist RNA polymerase binding

Answer 5

positive regulation

Question 6

Repressors bind to operators (sequence-specific) to prevent RNA polymerase binding

Answer 6

negative regulation

Question 7

Can bind to regulatory proteins to allow or prevent binding to DNA

Answer 7

allosteric effectors

Question 8

Genes in an operon are transcribed as…

Answer 8

polycistronic RNAs

Question 9

Bacterial exchange of DNA: partial genome transfer by DNA uptake

Answer 9

transformation

Question 10

Bacterial exchange of DNA: plasmid transfer, results in partial genome transfer

Answer 10

Conjugation

Question 11

Bacterial exchange of DNA: transfer as part of viral genome

Answer 11

transduction

Question 12

Merodiploids

Answer 12

partial diploids resulting from conjugation

Question 13

Negative Regulation of Lac Operon: is transcribed and translated continuously

Answer 13

Lac repressor (lacI)

Question 14

Negative Regulation of Lac Operon: repressor binds to ____ of the operon and blocks transcription of lac operon genes

Answer 14

Lac operator (lacO)

Question 15

Negative Regulation of Lac Operon: In the presence of the ______, the repressor undergoes a conformational change and can no longer bind to the operator

Answer 15

inducer (lactose, allolactose)

Question 16

MUST be physically linked and spatially very close to the DNA that is regulated

Answer 16

cis

Question 17

a molecule that is separate from the DNA that is regulated

Answer 17

trans

Question 18

One mutation affects many things

Answer 18

pleiotrophy

Question 19

• mutation of lacI makes lac operon genes constitutive
• presence of functional lacI suppresses mutant phenotype (lacI- is recessive)
  -lacI is trans-acting (repressor protein is separate from lac operon)

Answer 19

Lac I findings from Pardee, Jacob, and Monod study

Question 20

• Mutation of lacO makes lac operon genes constitutive
• presence of functional lacO does not suppress mutant phenotype (lacOc is dominant)
• lacO is cis-acting (sequence is within lac operon)

Answer 20

Lac O findings from Pardee, Jacob, and Monod study

Question 21

Positive regulation of the lac Operon: _____ activator that binds to the CAP binding site

Answer 21

Catabolite Activation Protein (CAP)

Question 22

Positive regulation of the lac Operon: CAP can bind to DNA when it is bound to ______

Answer 22

cAMP

Question 23

-araA, araB, and araD encode for enzymes that break down arabinsose
-araC encodes for an activator protein when bound to arabinose
-CAP-cAMP also activates this operon
- In absence of arabinose, araC binds both the I site and the O site to repress transcription

Answer 23

Regulation of the ara Operon

Question 24

contains genes that encode for enzymes that catalyze reactions needed for the production of tryptophan in E. coli

Answer 24

trp operon

Question 25

trp operon: tryptophan is a ________ that binds to a repressor and activates it through allosteric activation

Answer 25

corepressor

Question 26

trp operon enzymes are produced only when Trp levels are low and Trp production is thus needed

Answer 26

the trp Operon is Repressible

Question 27

- contains a start codon and two codons that encode for tryptophan - RNA produced can base pair with itself to form a secondary structure

Answer 27

trp Operon leader sequence

Question 28

- even in the presence of tryptophan, there is some level of transcription of the trp operon-- but the transcripts are terminated prematurely - transcription is attenuated - formation of a stem loop in the mRNA determines transcription termination - ribosome stalling (waiting for tRNA-Trp) influences hairpin formation

Answer 28

Rate of translation affects trp Leader RNA structure

Question 28

attenuated

Answer 28

greatly reduced, not completely turned off

Question 29

- Leader region is completely translated - formation of stem and loop in attenuator region results in the termination of transcription

Answer 29

High tryptophan level

Question 30

- ribosome is stalled at trp codons in leader region - transcription continues

Answer 30

low tryptophan levels