Chapter 6: 6.9 Prokaryotic Operons: Lactose (Lac) Operon

Question 1

In bacteria, related genes are ——— and ——– together in a structure known as an ——

Answer 1

• Regulated
• Expressed
• Operon

Question 2

True or False:

A single mRNA strand transcribed from an operon synthesizes only one protein

Answer 2

False, it can synthesize multiple proteins

Question 3

What does the Lac Operon encode?

Answer 3

Encodes for enzymes needed to utilize lactose as an energy source (LacZ, LacY, LacA)

Question 4

Is the Lac operon positively regulated?

Answer 4

No, it is negatively regulated

Question 5

What is LacI?

Answer 5

A repressor protein that negatively regulates the Lac Operon

Question 6

What is the inducer for the Lac Operon?

Answer 6

Lactose

Question 7

In a Lac Operon:

What happens when lactose is present?

(3 points)

Answer 7

• Binds to LacI
• LacI releases from the operator
• Transcription occurs

Question 8

In a Lac Operon:

What happens why lactose is absent?

(3 points)

Answer 8

• LacI stays bound to the operator
• Blocks RNA polymerase
• No transcription of the operon

Question 9

What is the Lac Operon negatively regulated?

Answer 9

Ensures no energy/resources are wasted transcribing and translating when it is not needed