Gene Regulation

Question 1

(sigma factors are important)

Answer 1

See lecture 4 for sigma factors

Question 2

Draw lac operon diagram

Answer 2

(see notes for diagram)

Question 3

What are attenuators?

Answer 3

RNA sequences able to form >1 secondary structure , often involve short leader sequence which needs tightly regulated transcription and translation

Question 4

What is the Trp operon?

What happens at low and high Trp?

Answer 4

Invovled in tryptophan biosynthesis
At high Trp ribosome translates leader sequence allowing formation of specific termination hairpin in mRNA that makes RNA pol fall off
(Remember transcription and translation coupled in bacteria)
If Trp low ribosome pauses at Trp codons resulting in different RNA structure so RNA pol continues

Question 5

What is the Trp operon also under control of?

Answer 5

A repressor protein

Question 6

Overall how much variation is possible in Trp operon expression?

Answer 6

700-fold

Question 7

What enzyme catalyses acetylation of lysine residues on histones?

Answer 7

Histone acetylytransferases

Question 8

What does lysine acetylation do?

Answer 8

Opens up chromatin and promotes transcription

Question 9

Epigenetic changes are…

Answer 9

Heritable but not explained by DNA sequence changes

Question 10

What are categories of epigenetic changes?

Answer 10

1) Cellular memory/control - often induced by tissue-specific TFs during early development and influences cell phenotype and differentiation
2) Trancriptional memory/control - environmentally induced epigenetic changes allow cells to be ‘primed’ for repeat challenges
3) Transgenerational memory/control - modification maintained even if stress removed, change follows after meiosis

Question 11

Eukaryotic transcription has more…

Answer 11

Accessory factors

Question 12

What are examples of eukaryotic transcription accessory factors? (another word for TF) What do they do?

Answer 12

TATA- binding protein and Trancription Factor 11a (TF11A)

Important for RNA pol recruitment, can be up-regulated in response to stimuli, can also repress gene expression

Question 13

What does the promoter region allow?

Answer 13

Transcriptional activators to aid recruitment of transcriptional machinery

Question 14

Describe transcription factors

Answer 14

Bipartite (2 parts), have very specific DNA binding domain (with zinc-fingers) and activation domain

Question 15

What is alternate splicing and what does it do?

Answer 15

Inclusion/exclusion of specific exon casettes leading to expression of many protein isoforms
Drastically enhances transcriptome diversity

Question 16

D.Melaogaster alternate splicing leads to how many isoforms?

Answer 16

38,016 (see notes for diagram)

Question 17

What are small RNAs and how long are they?

Answer 17

18-26 nt long, regulate gene expression, incliude miRNAs, shRNAs and siRNAs (micro, short hairpin, small intefering)
Can result in mRNA degredation, translation inhibition or gene silencing
Often used by RNA viruses to disrupt infected cell

Question 18

What can small RNAs do in terms of small changes in a stimulus?

Answer 18

Act as a buffer to protect biological pathways from small pertunbations