Lecture 6 - Prokaryotic Gene Regulation

Question 1

What does a gene include?

Answer 1

The regulatory elements that control its transcription

Question 2

What is the central dogma of molecular biology (direction of information flow in cells)?

Answer 2

Replication, DNA, transcription, RNA, translation, protein

Question 3

Transcription and translation occur only after what?

Answer 3

Induction

Question 4

Transcription and translation is _____ in prokaryotic cells, but ____ in eukaryotic cells

Answer 4

coupled, separated

Question 5

The pivitol point of control for gene expression in prokaryotic cells is often at the site of transcriptional initiation, which is what?

Answer 5

the promoter

Question 6

What are the three methods to identify the sequence of a bacterial promoter?

Answer 6

• Sequence DNA fragments protected by RNA polymerase from digestion with deoxyribonuclease
• align sequences upstream of the initiation site of transcription
• analyze mutants with enhanced or diminished rates of transcription

Question 7

What are the three stages of RNA synthesis?

Answer 7

Initiation, Elongation, Termination

Question 8

What happens in the initiation stage of RNA synthesis?

Answer 8

RNA polymerase recognizes a promoter, melts the TATA box, and initiates the incorporation of the first ribonucleoside triphosphates into the nascent RNA

Question 9

What happens in the elongation stage of RNA synthesis?

Answer 9

growth of the RNA polymer in the 5’ to 3’ direction

Question 10

What happens in the termination stage of RNA synthesis?

Answer 10

synthesis of the RNA polymer stops at precisely defined sites coded by the DNA template

Question 11

The core enzyme (RNA polymerase) consists of what?

Answer 11

• 2 copies of the alpha subunit

- one copy of each of the beta, beta prime and omega subunits

Question 12

What is the omega subunit not essential for?

Answer 12

for transcription, but it helps stabilize the RNA polymerase

Question 13

What is required for promoter recognition and initiation of transcription?

Answer 13

the holoenzyme ( 2 alpha subunits, 1 beta subunit, 1 beta prime subunit, 1 sigma subunit)

Question 14

When is the sigma factor released from the holoenzyme?

Answer 14

after initiation, to participate in recognition of other promoters

Question 15

What completes elongation and termination of the RNA transcript?

Answer 15

the core enzyme ( 2 alpha subunits, 1 beta subunit, 1 beta prime subunit)

Question 16

What is the irreversible step in initiation of transcription transition?

Answer 16

going from a closed-promoter complex to a open-promoter complex

Question 17

What are the two types of metabolic pathways?

Answer 17

• catabolic pathway: breakdown chemicals

- anabolic pathways: build up chemicals

Question 18

Who discovered the regulation of the lactose operon?

Answer 18

Jacob and Monod

Question 19

Low levels of beta-galactosidease in the bacterial cell converts lactose to what?

Answer 19

allolactose (an isomer of lactose), the actual inducer of the lactose operon

Question 20

What does the binding of the lactose repressor protein to the operator do?

Answer 20

blocks the transcription of the operon

Question 21

Is the conformational transition of the lactose repressor upon binding allolactose a reversible or non-reversible process?

Answer 21

a reversible process

Question 22

Regulatory proteins undergo a conformational change upon binding to what?

Answer 22

• a small molecule (ligand) that decrease or increases its affinity (binding) for DNA

Question 23

What are proteins that undergo a conformational change upon binding a ligand, such as repressor proteins called?

Answer 23

Allosteric proteins