Mod 6 Ch. 15

Question 1

Combinatorial control refers to the phenomenon that..

Answer 1

The combination of many factors determines the expression of any given gene

Question 2

A regulatory transcription factor protein typically contains ___ that binds to the ___ of the DNA.

Answer 2

An alpha helix, major groove

Question 3

A bidirectional enhancer has the following sequence:
5’-GTCA-3’
3’-CAGT-5’

Which of the following sequences would also be a functional enhancer?

Answer 3

5’-TGAC-3’

3’-ACTG-5’

Question 4

Regulatory transcription factors can be modulated by..

Answer 4

• the binding of small effector molecules
• protein-protein interactions
• covalent modifications

Question 5

A chromatin-remodeling complex may..

Answer 5

• change the locations of nucleosomes
• evict nucleosomes from DNA
• replace standard histones with histone variants

Question 6

According to the histone code hypothesis, the pattern of histone modifications acts like a language that..

Answer 6

Influences chromatin structure

Question 7

Which of the following characteristics is typical of a eukaryotic gene that can be transcribed?

Answer 7

The core promoter is found in a nucleosome-free region

Question 8

Transcriptional activation of eukaryotic genes involves which of the following events?

Answer 8

All of the above

• changes in nucleosome locations
• changes in histone composition within nucleosomes
• changes in histone modifications

Question 9

How can methylation affect transcription?

Answer 9

• it may prevent the binding of regulatory transcription factors
• it may enhance the binding of regulatory transcription factors
• it may attract the binding of methyl-CpG-binding proteins, which inhibit transcription

Question 10

The process in which completely unmethylated DNA becomes methylated is called..

Answer 10

De novo methylation

Question 11

Insulators may exert their effect by..

Answer 11

• acting as a barrier to changes in chromatin structure

- blocking the effects of neighboring enhancers

Question 12

Which of these levels is the most energy-efficient way to regulate gene expression?

Answer 12

Transcriptional regulation, because a cell avoids wasting energy making RNA or protein

Question 13

Explain how an alpha helix is able to function as a recognition helix in a transcription factor protein.

Answer 13

It can bind into the major groove of DNA and recognize a specific sequence of bases

Question 14

If a repressor prevents TFIID from binding to the TATA box, why does this inhibit transcription?

Answer 14

RNA polymerase will not be recruited to the core promoter

Question 15

When an activator protein interacts with mediator, how does this affect the function of RNA polymerase?

Answer 15

Causes mediator to phosphorylate CTD, which causes RNA polymerase to proceed to the elongation phase of transcription

Question 16

Explain why the glucocorticoid receptor binds next to the core promoter of some genes, but not next to the core promoter of most genes.

Answer 16

Binds only next to genes that have a GRE by their core promoters

Question 17

How might nucleosome eviction affect transcription?

Answer 17

May allow certain proteins access to binding to particular sites in the DNA

Question 18

Describe two ways that histone modifications may alter chromatin structure.

Answer 18

May directly affect the interaction between histones and the DNA, or they may affect the binding of other proteins to the chromatin

Question 19

Why is an NFR needed at the core promoter for transcription to occur?

Answer 19

So that activators can recognize enhancers and then the preinitiation complex can form

Question 20

Explain why histone eviction is needed for the elongation phase of transcription.

Answer 20

Because RNA polymerase cannot transcribe through nucleosomes

Question 21

What is the difference between be novo methylation and maintenance methylation?

Answer 21

De novo methylation occurs on unmethylated DNA

Maintenance methylation occurs on hemimethylated DNA

Question 22

Why are insulators important for gene regulation in eukaryotes?

Answer 22

They prevent one gene from regulating a neighboring gene. This allows each gene to control its own regulation