Prokaryotic Gene Regulation

Question 1

Two examples of negative regulation

Answer 1

1. enzyme repression in arginine operon

2. enzyme induction in lactose operon

Question 2

1 example of positive gene regulation

Answer 2

1. Maltose regulation system in E. coli

Question 3

arginine

Answer 3

corepressor

Question 4

What does arginine allosterically bind to?

Answer 4

arginine precursor (repressor protein)

Question 5

What genes are subject to end product repression?

Answer 5

anabolic (biosynthetic) genes

Question 6

What are catabolic (degradative) genes induced by?

Answer 6

starting substrates

Question 7

What does negative gene regulation involve?

Answer 7

Regulation of the repressor protein

Question 8

What does positive gene regulation involve?

Answer 8

Regulation of the activator protein

Question 9

catabolite repression

Answer 9

process whereby during catabolism of one carbon substrate, the catabolism and uptake of other poorer carbon substrates is prevented

Question 10

Two requirements for lac operon to be transcribed

Answer 10

1. cAMP present to bind to CRP

2. allolactose/suitable inducer present to bind to LacI repressor protein

Question 11

Lac operon regulation when glucose is PRESENT

Answer 11

Glucose prevents cAMP synthesis and stimulates its transport out of the cell

meaning cAMP cannot bind to CRP and so lac operon is NOT transcribed

Question 12

Regulon

Answer 12

multiple operons under control of a single regulatory protein

Question 13

Operon

Answer 13

one + genes transcribed into single mRNA and under control of single regulatory site

Question 14

During catabolite repression when both glucose and lactose are present, what is happening in the LAG PHASE?

Answer 14

Synthesis of beta-galactosidase enzymes (that are about to start catabolising lactose)