Regulation of Gene expression

Question 1

To exert transcriptional control, 3 genetic regulatory elements are needed

Answer 1

1. a regulatory gene (gene that encodes a repressor protein)
2. promoter (sequence that RNAP binds to)
3. operator (the place that a repressor binds to)

Regulator, promoter, operator, gene itself

Question 2

Inducers and Repressors

Answer 2

Inducer: binds to the repressor protein to weaken its affinity for the operater binding site

Repressor: binds tightly to the operator in a tethered dimer configuration

Question 3

Negative regulation

Answer 3

Molecular signal causes the dissociation of a repressor protein from the operator–> activation of gene

Molecular signal causes the binding of a repressor to DNA operator> inactivation of gene

Question 4

Positive regulation

Answer 4

Activator (protein that binds to RNAP not the DNA)

Signal causes the activator to the dissociate The RNAP or the binding of RNAP

Question 5

Catabolite repression

Answer 5

E coli would rather use glucose before lactose, so it can sense glucose levels via cAMP ( when glucose is low, cAMP levels go up)

cAMP binds to CAP (catabolite activator protein) camp/cap bind to a promoter region RNAP and start making lactose

Question 6

how does the lac operon get turned on

Answer 6

Lactose needs to be present so that it can form allolactose and bind to the repressor to have it come off of the operator

Glucose needs to be low so that camp levels go up and cause the dimerization of camp and CAP and they can both bind to the promoter and and strat RNAP do its job

Question 7

Gene regulation in Eukaryotes vs Prokaryotes

Answer 7

Prokaryotes: polycistronic mRNAs, coupled transcription and translation

Eukaryotes: monocistronic mRNAS, uncoupled transcription and translation, complex promoter regulatory elements

Question 8

Gene regulation in eukaryotes

Answer 8

Access of eukaryotic promoters to RNAP is hindered by heterochromatin structure so you need to remodel chromatin to activate a gene

Positive regulation mechanisms predominate and are required for basal level gene expression

Eukaryotic gene expression has a complicated set of proteins

RNAP 2 binding to a eukaryotic promoter requires 5 proteins:
Transcription activators (enhancers that bind upstream)
Coactivators (act indirectly)
Basal transcription factors
Architectural regulators to facilitate DNA looping
Chromatin Modification proteins

Question 9

Initiation Complex

Answer 9

You have an initiator region, and upstream you have a TATA box

you need basal transcription factors to assemble the preinitiation complex (the rate limiting step of transcription)

enhancers increase the rate of binding proteins

Closed-> Open-> promoter clearance-> elongation

Question 10

Enhancers

Answer 10

enhancers are upstream aka (UAS) that bind to DNA and allow RNAP 2 to bind better to the promoter region

Question 11

Eukaryotic transcriptional regulators have discrete functiional domains

Answer 11

1. DNA binding
2. factor dimerization
3. transcriptional activity