Operons

Question 1

What is the purpose of control of gene expression in prokaryotic cells?

Answer 1

Saves energy by only making proteins needed at a particular time

This allows the cell to efficiently manage resources.

Question 2

What percentage of genes in prokaryotes are not regulated?

Answer 2

60-80%

These genes are constantly produced at a fixed rate.

Question 3

What are operons in prokaryotes?

Answer 3

Groups of genes located side by side that work together

Operons can turn genes on and off.

Question 4

What are the components of the Operon Model?

Answer 4

• Regulatory Gene (I)
• Promoter (P)
• Operator (O)
• Structural Genes (Z, Y, A)

Each component plays a role in gene transcription regulation.

Question 5

Regulatory Gene

Answer 5

Makes repressor protein

Question 6

Promoter

Answer 6

The reigon of DNA where RNA plymerase initiates transcription

Question 7

Operator

Answer 7

Like a traffic light that acts as a stop or go signal for the transcription of the genes

Question 8

Structural Genes

Answer 8

Determine which protein gets made

Question 9

What does induction do in gene expression?

Answer 9

Turns ON transcription when a particular product IS present

Example: lac operon in E. coli when lactose is present.

Question 10

What happens to the lac operon when lactose is absent?

Answer 10

The regulatory gene produces a protein that blocks RNA polymerase

This prevents transcription of genes for breaking down lactose.

Question 11

What is repression in gene expression?

Answer 11

Turns ON transcription when a particular product is NOT present

Example: Trp operon promotes tryptophan production when tryptophan isn’t present.

Question 12

What is a repressible operon?

Answer 12

Always transcribed unless deactivated by a repressor

Example: Tryptophan operon, which is normally active.

Question 13

What role does tryptophan play in the Tryptophan Operon?

Answer 13

Acts as a corepressor binding to the repressor protein

This binding stops further tryptophan synthesis when excess tryptophan is present.

Question 14

Operons are only in…

Answer 14

Prokaryotic cells (bacteria)