(Dr. Heinemann) (Unit C) Topic 19

Question 1

What is different between transcription in prokaryotes and eukaryotes?

Answer 1

1. Timing (can do replication and transcription at the same time for prokaryotes)
2. Spatial separation (replication and transcription occur in separate places in eukaryotes)

Question 2

What are potential points of replication in gene expression in eukaryotes?

Answer 2

1. Transcription control (DNA to RNA transcript)
2. RNA processing control (RNA transcript to mRNA)
3. RNA transport and localization control (transport from nucleus to cytosol)
4. mRNA degradation control (mRNA to inactive mRNA)
5. Translation control (mRNA to protein)
6. Protein activity control (protein to inactive/active protein)

Question 3

What does the eukaryotic transcription initiation complex comprise of?

Answer 3

• RNA polymerase II (different from prokayotes)
• 5 general transcription factors (GTFs)
• Multi-subunit complex (mediator)

Question 4

What are eukaryotic transcription factors equivalent to?

Answer 4

Sigma subunit in bacteria

Question 5

How do eukaryotic RNA polymerases interact with their promoters?

Answer 5

GTFs that recognize the TATA box element/promoter element

Question 6

Transcription activators vs. Transcription repressors

Answer 6

Transcription activators
* Bind to enhancer elements that can be distant from the TATA element

Transcription repressors
* Bind to silencer elements in a similar manner

Question 7

Bacteria vs. Eukaryotes:

Polymerases and termination

Answer 7

Prokaryotes
* Single RNA polymerase
* Requires sigma subunit to initiate
* Sometimes require Rho to terminate

Eukaryotes
* 3 RNAP
* Requires GTFs (TFIID) to initiate
* No Rho required

Question 8

Bacteria vs. Eukaryotes:

Operons

Answer 8

Bacteria
* Operons, multiple genes expressed per operon

Eukaryotes
* No operons, only a single gene expressed

Question 9

Bacteria vs. Eukaryotes:

Promoter structure

Answer 9

Eukaryotes
* Don’t have -10 and -35 sequences
* No sigma factor
* Has TATA box along with other regions

Question 10

How is promoter recognition done in eukaryotes?

Answer 10

Determined by a set of proteins
* Recognizes TATA box and binds

Question 11

Bacteria vs. Eukaryotes:

Regulatory protein binding sites

Answer 11

Eukaryotes
* Regulatory proteins often bind DNA several thousand base pairs from the start site

Question 12

What is the purpose of the mediator?

Answer 12

Since multiple regulatory proteins bind to the promoter
* Enhancer regions only have on activator protein
* Cannot attach to multiple different receptors
* Mediator recognizes a combination of regulatory proteins and attaches to provide on single “switch”

Question 13

Bacteria vs. Eukaryotes:

Combinational control

Answer 13

Eukaryotes
* Groups of proteins work together to determine the expression of a gene