Regulation of Gene Expression

Question 1

what are operons in prokaryotes ?

Answer 1

Prokaryotic genes that encode proteins with related functions tend to be organized in clusters

Question 2

what are the 2 ways in which prokaryotes transcribe genes in prokaryotes ?

Answer 2

1. unducible
2. repressible

Question 3

what are the 2 types of operon on prokaryotes ?

Answer 3

• *Lac *operon
• Trp operon

Question 4

where does gene expression in eukaryotes occur ?

Answer 4

can occur at many different levels

Question 5

Control of Eukaryotic Gene Expression

Answer 5

1. transcriptional control
2. RNA pressing control
3. RNA transposrt and localization control
4. Translation control
5. mRNA degradetion control
6. Protein activity control

Question 6

what is the additional regulatory element in eukaryotes ?

Answer 6

An enhancer

Question 6

what is the additional regulatory element in eukaryotes ?

Answer 6

An enhancer

Question 7

what do enhancers do ?

Answer 7

• control whether a promoter is active or inactive in a cell or at a particular time
• can determine whether or not the general transcription factors can bind to the promoter and initiate transcription

Question 8

what do enhancers do ?

Answer 8

• control whether a promoter is active or inactive in a cell or at a particular time
• can determine whether or not the general transcription factors can bind to the promoter and initiate transcription

Question 9

where are eukaryotic promoters found?

Answer 9

• Both lie adjacent to and upstream of the transcriptional start site
• Both contain a TATA box

Question 10

main differences between prokaryotic and eukaryotic promoters

Answer 10

• Eukaryotic promoters are larger and more complex
• They contain a CAAT box
• Eukaryotic RNA polymerase II requires additional factors to bind to the promoter: General transcription factors

Question 10

main differences between prokaryotic and eukaryotic promoters

Answer 10

• Eukaryotic promoters are larger and more complex
• They contain a CAAT box
• Eukaryotic RNA polymerase II requires additional factors to bind to the promoter: General transcription factors

Question 11

What is a TATA Box ?

Answer 11

• a component of the eukaryotic core promoter and generally contains the consensus sequence (5’-TATA(A/T)A(A/T)-3’)
• Considered a non-coding DNA sequence (cis-regulatory element)
• binding site of the TATA-binding protein (TBP) and other transcription factors in some eukaryotic genes
• the site of preinitiation complex formation, which is the first step in transcription initiation in eukaryotes

Question 12

Six Key General Transcription Factors

ALPHABETICAL ORDER , NOT ACTUAL ORDER

Answer 12

1. TFIIA
2. TFIIB
3. TIID
4. TFIIE
5. TFIIF
6. TFIIH

Question 13

what does TFIIA do ?

Answer 13

Stabilizes the interaction between the TATA box and TFIID/TATA binding protein (TBP)

Question 14

what does TFIIB do ?

Answer 14

Recorgnizes the BRE element in promoters

Question 15

what does TFIID do ?

Answer 15

binds to TBP and recorgnizes TBP associates factors (TAFs), also adds promoter selectivity

Question 16

What does TFIIE do ?

Answer 16

attracts and regukates TFIIH

Question 17

what does TFIIF do ?

Answer 17

• stabilizes RNA polymerase interaction with TBP and TFIIB
• helps attract TFIIE and TFIIH

Question 18

what does TFIIH do ?

Answer 18

• Unwinds DNA at the transcription start point * Phosphorylates Ser5 of the RNA polymerase CCTD
• Releases RNA polymerase from the promoter

Question 19

what does TFIIH do ?

Answer 19

• Unwinds DNA at the transcription start point * Phosphorylates Ser5 of the RNA polymerase CCTD
• Releases RNA polymerase from the promoter

Question 20

the helix–turn–helix (HTH) motif

Answer 20

• present in eukaryotes and prokaryotes
• charactherised by a geometric conformation rather than an amino acid sequence
• presence of 2 addjecent aplha helices seperated by a turn of amino acids

Question 21

Zinc-finger motif

Answer 21

• found in wide range of transcription factors that regulate gene expression related to cell growth, development and differentiation
• typically it contins clusters of 2 cysteines and 2 histidates –> they interact with zinc atom to fold into loops wit specific DNA sequences

Question 21

Zinc-finger motif

Answer 21

• found in wide range of transcription factors that regulate gene expression related to cell growth, development and differentiation
• typically it contins clusters of 2 cysteines and 2 histidates –> they interact with zinc atom to fold into loops wit specific DNA sequences

Question 22

How can chromatin be modified ?

Answer 22

• Changes to nucleosomes – Histone modifications and variants
• Modifications to DNA – DNA methylation (typically acts as a repressor)