Topic 5

Question 1

regulatory proteins

Answer 1

either activate or repress transcriptional machinery
- bind to DNA
- interact w transcriptional machinery
- interact w other proteins
- chromatin domains (euk. only)
- physiological sensor domains

Question 2

operon

Answer 2

a group of genes expressed together, usually as a polycistronic transcript
- prokaryotes ONLY

Question 3

Positive control

Answer 3

needs an activator to turn on expression
-default is off

Question 4

Negative control

Answer 4

needs a repressor to turn off expression
- default is on
- ie. lac operon

Question 5

Inducible

Answer 5

an effector/inducer is needed to change expression (usually allosterically)

Question 6

mirozygote

Answer 6

partial diploids
- E. coli carrying an F episome

Question 7

episome

Answer 7

plasmid, extrachromosomal circular DNA

Question 8

lacZ

Answer 8

beta-galactosidase coding gene

Question 9

lacY

Answer 9

permease coding gene

Question 10

lacA

Answer 10

transacetylase coding gene

Question 11

palindromic

Answer 11

read the same backwards as forwards, usually bound by dimeric proteins

Question 12

CAP

Answer 12

catabolite activator protein

Question 13

cAMP

Answer 13

cyclic adenosine monophosphate
- activates lac operon when there is low glucose

Question 14

araC

Answer 14

alone: binds to both O and I, sterically preventing transcription (REPRESSOR)
+ arabinose: binds only I, allowing transcription (ACTIVATOR)

Question 15

polycistronic

Answer 15

multiple proteins are encoded on a single mRNA strand

Question 16

biochemical pathways are usually ________ systems

Answer 16

negative
-repressor usually binds to operator when end product is present

Question 17

attenuation

Answer 17

controls transcription prematurely by forming an intrinsic hairpin structure in response to a trigger (high trp levels)

Question 18

Promoter-proximal elements

Answer 18

upstream promoter elements
- bind GTFs
- CCAAT box @ -100bp
- GC rich region @ -200bp

Question 19

Distance-independent elements

Answer 19

silencers/enhancers
- up to 50kbp away from gene
- orientation independent
- use DNA looping to interact w RNA polymerase

Question 20

SOX1

Answer 20

binding of enhancer in crystallin genes

Question 21

enhancesome

Answer 21

large complex that acts synergistically to activate transcription