Midterm #2 Material - Push to Final

Question 1

What is polycistronic?

Answer 1

The single mRNA carrying multiple protein-coding sequences

Question 2

What is the lac operon designed for?

Answer 2

E.coli to break down lactose

Question 3

What are the different parts of the operon?

Answer 3

PROG (Promoter, Repressor, Operator, Gene)

Question 4

How is lactose transported?

Answer 4

via LacY permease

Question 5

What does beta-galactosidase do?

Answer 5

Cleaves lactose to glucose and galactose

Question 6

What happens to the operon when lactose isn’t present?

Answer 6

The lac operon is repressed by Lac1.

Question 7

What are the independent translation control signals of an operon?

Answer 7

1) RBS (Ribosomal Binding Site)
2) Start Codon
3) Stop Codon

Question 8

What is catabolite repression?

Answer 8

When a preferred carbon source is available, genes involved in the metabolism of other carbon sources is repressed.

Question 9

What does the induction of lac operon require?

Answer 9

1) High cAMP-CRP Concentration
2) Presence of lactose

Question 10

What is cyclic AMP synthesized from?

Answer 10

ATP via adenylate cyclase

Question 11

At what type of concentrations is cAMP effective at?

Answer 11

very low

Question 12

What does CRP stand for and what gene is it encoded by?

Answer 12

1) Catabolite Repressor Protein
2) crp gene

Question 13

What is CRP?

Answer 13

A gene regulatory protein that binds cAMP

Question 14

CAP Site

Answer 14

Region of the lac promoter (lacP) at which cAMP-CRP binds to

Question 15

What is the critical parameter in gene regulation by catabolite repression?

Answer 15

Concentration of cAMP

Question 16

What can neither crp or cya utilize?

Answer 16

Alternative C sources

Question 17

What are the conditions when glucose is abundant?

Answer 17

1) low concentration of cAMP-CRP
2) Not enough cAMP-CRP to bind to lacP
3) lac operon is not expressed

Question 18

What are the things lac operon induction requires?

Answer 18

1) Binding of cAMP-CRP to lacP
2) Absence of lacI repressor at lacO site

Question 19

What is the actual inducer of the lac operon?

Answer 19

allolactose

Question 20

What happens when there’s an absence of lactose (allolactose) or IPTG?

Answer 20

LacI-repressor binds to lacO, preventing transcription

Question 21

Why is IPTG often used as inducer rather than lactose?

Answer 21

Because of its constant level

Question 22

What are the advantages of plasmids?

Answer 22

Antibiotic resistance, toxin degradation, virulence and/or symbiosis-related functions

Question 23

What do Col plasmids do?

Answer 23

Synthesize colicin proteins

Question 24

What are colicin proteins?

Answer 24

Type of bacteriocin unique to E.coli strains

Question 25

What are bacteriocins?

Answer 25

Proteins that can kill sensitive bacteria

Question 26

What are R Plasmids (Resistance)?

Answer 26

They carry resistance to antibiotics and other factors

Question 27

What are characteristics of R Plasmids?

Answer 27

Often broad-host-range and self-transmissible