Gene Expression and Regulation in Eukaryotes

Question 1

What is the principal difference between regulation of transcription in eukaryotes and prokaryotes?

Answer 1

In eukaryotes, the ground state is that heterochromatin is off - gene is not open to RNA pol II. The heterochromatin has to remodel to facilitate RNA pol II to be active.

Question 2

How is regulation controlled in eukaryotes?

Answer 2

Remodeling unwinds the heterochromatin to expose the promoter region for transcription.

Question 3

Histone acetylation usually leads to

Answer 3

Activation

Question 4

Histone methylation usually leads to

Answer 4

Supression

Question 5

What do enhanceosomes recruit?

Answer 5

Chromatin remodelers

Question 6

What does the ehanceosome form a binding site for? And what does it do?

Answer 6

GCN 5 complex binds to enhanceosome and adds acetyl groups to nuc 1 and 2

Question 7

The acteylation of the nucleosomes exposes the TATA box, what happens next?

Answer 7

TATA binding protein (TBP) binds to the TATA box which allows transcription to begin

Question 8

What is gene silencing caused by?

Answer 8

The spread of heterochromatin

Question 9

How do you stop the spread of heterochromatin?

Answer 9

Barrier insulater between heterochromatin and euchromatin?

Question 10

How does the barrier insulator work?

Answer 10

Barrier insulator attracts HAT protein which removes methylation on surrounding histone tails and acetylates the histone tails on either side causing inactivation

Question 11

How are the 2 X chromosomes in females regulated?

Answer 11

The first gene to bind to protein YY1 in the vicinity of a bound PRC2 will be inactivated and the other X chromosome will be inactivated.

Question 12

What is a UAS sequence in galactose genes?

Answer 12

Binding sites for activator self-expression protein

Question 12

What is a UAS sequence in galactose genes?

Answer 12

Binding sites for activator self-expression protein

Question 13

the Gal4 has what 3 domains?

Answer 13

Activation domain
dimerization domain
DNA-binding domain

Question 14

What does the DNA binding domain do?

Answer 14

Binds to the upstream regulatory sequences of the genes

Question 15

What does the activation domain do?

Answer 15

Attracts DNA polymerase and regulatory components and starts expression of the gene

Question 16

How can Gal4 regulate genes on separate chromosomes?

Answer 16

When Gal4 is expressed in the cell, it can bind to all UAS sequences in the cell

Question 17

If Gal80 protein is bound to the activation domain of Gal4?
What causes it to dissociate?

Answer 17

The gene is still inactive wil Gal80 is bound?
Gal80 will disociate in the presence of galactose and Gal3 and the gene will be actively expressed

Question 18

Port-translational Regulation

What does the RISC complex do?

Answer 18

1. Prevent Cap binding
2. Interefere with elongation
3. Prevent Ribosome assembly
4. Remove poly A tail

Question 19

How do transcription factors control yeast sex?

Answer 19

Depending on what transcription factors are bound, they will deteremine what sex the yeast is

Question 20

How is yeast mating type controlled by recombination?

Answer 20

MATa active - a mating type
HMLalpha is copied into MATalpha locus- alpha mating type
HMRa is copied into MATalpha locus - a mating type

Question 21

Enhabcer-blocking insulator place holder

Question 22

Maternal mitochondria inhertance

What results in conflict?

Answer 22

Biparental inhertiance - conflict
Uniparental inhertiance - no clonflict