Gene Expression

Question 1

How is gene expression controlled in eukaryotics?

Answer 1

Transcription factors altering the rate of transcription of genes

Question 2

What are transcription factors?

Answer 2

Proteins that bind to DNA and activate/deactivate genes

Question 3

What are the two types of transcription factor in eukaryotes?

Answer 3

• Activators

- Repressors

Question 4

What do activators do? 2

Answer 4

• Increase rate of transcription

- Help RNA polymerase bind to DNA

Question 5

What do repressors do? 2

Answer 5

• Decrease rate of transcription

- Prevents RNA polyermase binding to DNA

Question 6

Where do transcription factors bind?

Answer 6

Start of target genes at specific DNA sites

Question 7

What does an operon contain?

Answer 7

• Structural genes
• Control elements [promoter/operator]
• Regulatory gene

Question 8

What type of cell contains operons?

Answer 8

Prokaryotes

Question 9

What are structural genes?

Answer 9

Genes coding for useful proteins functioning in cells

Question 10

What is the promoter region?

Answer 10

DNA sequence located before the structural genes RNA polymerase binds to

Question 11

What is the operator region?

Answer 11

DNA sequence transcription factors bind to

Question 12

What is the regulatory gene?

Answer 12

Transcription factors coding for the expression of other genes : activators/repressors

Question 13

What bacterium has the lac operon?

Answer 13

E.Coli

Question 14

What is the lac operon?

Answer 14

The section of DNA where the enzymes needed for digesting lactose are found

Question 15

What are 3 structural genes in the lac operon?

Answer 15

• Lac Z
• Lac A
• Lac Y

Question 16

What do 3 the structural genes in the lac operon code for?

Answer 16

• Beta galactosidase

- Lactose Permease

Question 17

What are beta galactosidase and lactose permease?

Answer 17

Proteins helping bacteria digest lactose

Question 18

What is the regulatory gene in the lac operon called?

Answer 18

Lac I

Question 19

What happens when lactose is absent?

Answer 19

• Regulatory gene [lacI] produces lac repressor protein
• Binds to the operator site
• Stops RNA polymerase binding to promoter region
• No transcription of structural genes

Question 20

What happens when lactose is present?

Answer 20

• Lactose binds to repressor protein
• It changes shape
• Can no longer bind to operator
• RNA polymerase can bind to promoter region
• Structural genes are transcribed and translated
• Beta galactosidase and lactose permease are made