chapter eighteen part one

Question 1

gene regulation in prokaryotes/unicellular eukaryotes

Answer 1

respond to different environmental cues
- feedback inhibition
- adjust activity of enzymes already present
- adjust production level of certain enzymes

Question 2

gene regulation in multicellular eukaryotes

Answer 2

• environmental cues
• developmental changes
• cell specialization/differentiation
  - expression of different genes in certain areas

Question 3

sites of gene regulation

Answer 3

1. transcription regulation
   - chromatin modification
   - transcription initiation
2. post-transcriptional regulation
   - alternative RNA splicing
   - mRNA degradation
   - mRNA location/availability
3. post-translational regulation
   - regulate protein activity (constitutive, regulated)
   - regulate protein lifespan

Question 4

where odes the most regulation occur

Answer 4

transcription regulation
- often in response to signalsc

Question 5

chromatin modification

Answer 5

1. DNA methylation - methylated regions where genes no expressed
2. histone protein methylation - condenses chromatin and reduces transcription
3. histone protein acetylation - addition of acetyl group to AA in histone tail loosens chromatin and promotes transcription

Question 6

transcription initiation

Answer 6

• key control point
• involves proteins that bind to DNA and inhibit/facilitate binding of RNA poly
• can vary in cell/tissue type

Question 7

alternative RNA splicing

Answer 7

from single pre-mRNA, multiple mRNA
- troponin (muscle protein)
- plasma B cell

Question 8

mRNA degradation

Answer 8

by enzymes
- hemoglobin mRNA in erythroblasts
- mRNAs usually stable for a while, translated repeatedly into red blood cells

Question 9

regulation of protein activity

Answer 9

reversible addition of phosphate groups. acquired sugars, transported to target destinations
- constitutive enzymes
- regulated enzymes

Question 10

constitutive enzymes

Answer 10

always there
- glycolysis, aminoacyl-tRNA synthetase
- most of bacterial enzymes, varies by cell type for multicellular euks

Question 11

regulated enzymes

Answer 11

inducible - on/off
- digestive/biosynthetic/cyclins
- fewer of bacterial enzymes, varies B cell type for multicellular euks

Question 12

operon

Answer 12

collection of several genes for one biosynthetic pathway and its regulatory regions

Question 13

regulatory regions of operon

Answer 13

promoter, operator, activator binding sites

Question 14

promoter

Answer 14

site for RNA poly to bind and begin transcription

Question 15

operator

Answer 15

controls access of RNA poly to genes
- where repressor proteins bind

Question 16

operons under negative control

Answer 16

use a repressor protein
1. repressible
2. inducible

Question 17

repressible operon (trp)

Answer 17

• anabolic enzymes
• by itself, trp operon turned on

Question 18

if no trp

Answer 18

operon turned on, repressor protein inactive, transcription of enzymes needed for trp synthesis produced

Question 19

if trp

Answer 19

operon off, trp binds to repressor (corepressor), repressor binds to operator, RNA pol access to promoter blocked, no enzymes for trp synthesis produced

Question 20

inducible operon (negative control) (lac)

Answer 20

• catabolic enzymes (using lactose as energy source)

Question 21

if no lac

Answer 21

operon turned off
- regulator produces repressor protein
- repressor by itself binds to operator
- RNA poly blocked, no enzymes for lac catabolism

Question 22

if lac

Answer 22

operon turned on
- lac binds to repressor protein (lac = inducer)
- repressor protein moved from operator/can’t bind
- RNA poly proceeds, enzymes for lac catabolism transcribed

Question 23

operons under positive control

Answer 23

• use activator protein
• inducible

Question 24

inducible (positive control) (lac)

Answer 24

• lac operon fine-tuned by being sensitive to glucose concentration
• if glucose low, then cAMP goes up and cAMP binds to CRP
• if glucose high, cAMP concentration falls, CPR detaches from lac operon

Question 25

what happened when cAMP binds to CRP

Answer 25

• it binds to DNA, increases tcr of lac operon