Prokaryotic gene expression

Question 1

The earlier the cell intervenes in the process of protein synthesis, the _______ energy it wastes. Thus, cells will tend to regulate protein synthesis _______.

Answer 1

less; at the earliest possible stage

Question 2

Operons involved in __ are typically inducible

Answer 2

Catabolism

Question 3

Operons involved in __ anabolism are typically repressible

Answer 3

Anabolic

Question 4

Constitutively expressed genes are generally _

Answer 4

unregulated

Question 5

How is the lac repressor gene expressed?

Answer 5

Constitutively

Question 6

What is the correct order of operon elements, assuming transcription is occuring from left to right?

Answer 6

Promoter, operator, structural genes?

Question 7

If the gene encoding the lac repressor is mutated so that the repressor can no longer bind the operator, will transcription of the lac operon occur?

Answer 7

Yes, because RNA polymerase will be able to bind the promoter and transcribe the operon

Question 8

The TATA box is a-

Answer 8

sequence in the promoter region of some genes

Question 9

An enhancer is

Answer 9

A DNA sequence several thousands on nucleotides distant from the promoter.
When bound by a protein, transcription rates increase greatly

Question 10

What are the stress response elements in plants

Answer 10

DNA sequences

Question 11

Name an example of regulation of eukaryotic transcription

Answer 11

Activator proteins binding to an enhancer

Question 12

What is the role of the protein sigma factor?

Answer 12

Sigma factor recognises and binds core promoter elements and recruits RNA polymerase

Question 13

How can DNA binding proteins regulate transcription (stimulate or repress)

Answer 13

The binding of a repressor/activator protein to a repressor/activator binding site

Question 14

Allosteric Regulation-

Answer 14

of enzyme-catalyzed reactions allows rapid fire-tuning

Question 15

Regulation of gene expression-

Answer 15

(regulation of the synthesis of enzymes) is slower but conserves resources

Question 16

How can inducers activate repressors or activators?

Answer 16

Inducers bind to either repressor/activator to change it’s conformation, allowing the opposite effect to take place

Question 17

Difference between inducer and constitutive proteins

Answer 17

Inducible promoters - synthesised only under certain conditions or on requirement Constitutive promoters - expressed all the time

Question 18

What proteins are involed in the uptake and metabolism of lactose in E.coli?

Answer 18

B-galactoside permease - carrier protein, moves sugar into the cell
B-galactosidase - hydrolyse lactose
B-galactoside transacetylase - transfer acetyl groups to certain B-galactoside

Question 19

What occurs if e.coli is grown with glucose but no lactose present?

Answer 19

No enzymes for lactose conversion are produced

Question 20

What if lactose is predominant and glucose is low in E.coli?

Answer 20

All three enzymes are synthesised

Question 21

What is an operon?

Answer 21

A cluster of genes with a single promoter that allows for genes to be co-regulated

Question 22

What does an operon consist of?

Answer 22

A promoter, two or more structural genes and an operator

Question 23

What is an operator?

Answer 23

a short stretch of DNA between the promoter and the structural genes

Question 25

What type of system is the lac Operon?

Answer 25

An inducible one

Question 26

In transcription, what role does lactose play in regulation?

Answer 26

Lactose binds to the repressor protein, changing it’s shape, therefore not allowing it to bind to the promoter, so RNA polymerase can bind so transcription can move ahead

Question 27

Inducible systems control _ pathways

Answer 27

Catabolic (breaks down molecules into smaller units with release of energy)

Question 28

Repressible systems control _ pathways

Answer 28

Anabolic (constructs molecules, energy required)

Question 29

lac Operon - Glucose present, no lactose

Answer 29

No transcription of lac genes, low cAMP levels, absent RNA polymerase